essay on omicron virus

Masks Strongly Recommended but Not Required in Maryland, Starting Immediately

Due to the downward trend in respiratory viruses in Maryland, masking is no longer required but remains strongly recommended in Johns Hopkins Medicine clinical locations in Maryland. Read more .

• Vaccines  
• Masking Guidelines
• Visitor Guidelines  

COVID Omicron Variant: What You Need to Know

Featured Experts:

Robert Bollinger, M.D., M.P.H.

Stuart Ray, M.D.

Throughout the COVID-19 pandemic, several coronavirus variants have emerged as the virus, SARS-CoV-2, continues to mutate and evolve. Many of these variants’ mutations have little or no impact on how the virus affects humans. But others, such as the genetic changes in the delta variant, can make the coronavirus more transmissible contagious) than the original version of SARS-CoV-2 that was discovered in late 2019.

In November 2021 , a variant of the SARS-CoV-2 coronavirus emerged, and was named omicron by the World Health Organization (WHO). WHO currently lists the omicron as a variant of concern. Stuart Ray, M.D. , vice chair of medicine for data integrity and analytics, and Robert Bollinger, M.D., M.P.H. , Raj and Kamla Gupta Professor of Infectious Diseases, are experts in SARS-CoV-2, and they address your questions about the omicron coronavirus variant.

Staying Safe This Holiday Season: COVID-19 Variants

President Kevin Sowers and Dr. Lisa Maragakis discuss the omicron variant, COVID-19 boosters and staying safe through the holidays.

Omicron: There is much to learn

Because of its recent emergence, scientists are just starting to learn about omicron, but intense research is quickly uncovering more insight on this variant and how its genetic changes might affect its spread and people who are infected with it. Bollinger and Ray say the next few weeks will provide even more clarity, and address some questions.

Is omicron more transmissible (contagious)?

“There is some preliminary evidence suggesting the omicron variant is more infectious than the delta variant,” says Bollinger. “But there is no evidence so far that the standard prevention strategies, including vaccination, masking, distancing, ventilation and hand-washing are not effective in reducing the risk of infection or transmission.”

Does omicron cause more severe COVID-19 illness?

“For omicron, there are very limited data on this,” Bollinger says. “But, so far, the answer appears to be no.  We will know more about this in the coming weeks.”

Do the COVID vaccines still work and reduce the risk of severe illness?

According to Bollinger and Ray, this is the most important question, and with so little data, a lot is still unknown.

“My own expectation is that being fully vaccinated, including boosters, will still provide a reduced risk of hospitalization and death,” Bollinger says. “In the weeks ahead, we will learn more about how well the antibodies induced by the current vaccinations can neutralize the omicron variant in the laboratory. If they can, that will be good news.

“I am also confident that if we find that the current vaccines are not providing optimal protection against severe disease or death due to this variant, we will be able to quickly modify the current vaccines to address omicron.”

Does the omicron variant show up on COVID tests?

The available commercial diagnostic PCR (polymerase chain reaction) and antigen COVID tests still appear to work to identify the omicron variant. We will know more in the coming weeks about how well the rapid at-home tests perform to detect the new variant.

Do the current antiviral drugs still work on omicron?

Some antiviral drugs work by limiting a virus’ ability to make copies of itself (replicate) in the body. Remdesivir is the only such antiviral drug currently authorized for emergency use by the Food and Drug Administration (FDA) to treat COVID-19. Two other antiviral drugs, one from Merck and one from Pfizer, are under FDA review to see if they, too, can be authorized.

“I have not seen any data so far,” Bollinger says, “that would suggest that these drugs would work less well for omicron than for any of the other variants. However, continued studies will reveal more about these mutations and potential impact the drugs may have on their viral replication.”

Do current monoclonal antibody (MAbs) treatments still work for people infected with the omicron variant?

“For other variants, providing high-risk infected and exposed patients with early access to MAbs reduces their risk of hospitalization and death by up to 70%.

“We do not know yet how well the current MAbs will work for the omicron variant, but we will know very soon how well they neutralize omicron in the lab,” Bollinger says. “If they do, this will be reassuring. If they do not, I am confident that we will be able to quickly modify the current MAbs to address this,” he says.

“We still have a lot to learn about omicron,” Ray says, “but we have tools at hand that enable individuals to manage risk, including wearing a high-quality mask, or respirators. Those rated FFP2 or FFP3 are more protective than cloth masks, and often easier to wear. Getting vaccinated and getting a COVID-19 booster, hand-washing and avoiding large indoor gatherings, especially with unmasked people, are other ways to mitigate the risk of infection.

“This new variant is a reminder that we should be using multiple tools for the safety of ourselves and those for whom we care.”

Learn more about variants .

After an Organ Transplant: 14 Strategies for Safer Living During the COVID-19 Era

Traveling After an Organ Transplant During the COVID-19 ERA

Información sobre la COVID-19

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

• View all journals
• Explore content
• About the journal
• Publish with us
• Sign up for alerts
• NEWS FEATURE
• 24 February 2022

Omicron’s lasting mysteries: four questions scientists are racing to answer

• Amber Dance 0

Amber Dance is a science journalist in Los Angeles, California.

You can also search for this author in PubMed   Google Scholar

Omicron infects the cells of the nose, throat and lungs differently from former variants. Credit: Lucas Landau/Reuters/Alamy

Infection rates with the Omicron variant of the coronavirus SARS-CoV-2 are plummeting in many countries around the world. But scientists are still struggling to understand how it spread so rapidly and what it might do next, especially because the subvariant known as BA.2 is rising in some places.

Access options

Access Nature and 54 other Nature Portfolio journals

Get Nature+, our best-value online-access subscription

24,99 € / 30 days

cancel any time

Subscribe to this journal

Receive 51 print issues and online access

185,98 € per year

only 3,65 € per issue

Rent or buy this article

Prices vary by article type

Prices may be subject to local taxes which are calculated during checkout

Nature 603 , 22-24 (2022)

doi: https://doi.org/10.1038/d41586-022-00428-5

Hui, K. P. Y. et al. Nature https://doi.org/10.1038/s41586-022-04479-6 (2022).

Article   PubMed   Google Scholar  

Peacock, T. P. et al. Preprint at bioRxiv https://doi.org/10.1101/2021.12.31.474653 (2022).

Abdelnabi, R. et al. Antiviral Res. 198 , 105253 (2022).

Hay, J. A. et al. Preprint at medRxiv https://doi.org/10.1101/2022.01.13.22269257 (2022).

Puhach, O. et al. Preprint at medRxiv https://doi.org/10.1101/2022.01.10.22269010 (2022).

Willet, B. J. et al. Preprint at medRxiv https://doi.org/10.1101/2022.01.03.21268111 (2022).

Wang, L. et al. Preprint at medRxiv https://doi.org/10.1101/2022.01.12.22269179 (2022).

Davies, M.-A. et al. Preprint at medRxiv https://doi.org/10.1101/2022.01.12.22269148 (2022).

Bojkova, D. et al. Cell Res . https://doi.org/10.1038/s41422-022-00619-9 (2022).

Shalamova, L. et al. Preprint at bioRxiv https://doi.org/10.1101/2022.01.20.476754 (2022).

Choi, S. J. et al. Cell. Mol. Immunol . https://doi.org/10.1038/s41423-022-00838-5 (2022).

Article   Google Scholar  

Shiliaev, N. et al. J. Virol. 95 , e01357-21 (2021).

Szemiel, A. M. et al. PLoS Pathog. 17 , e1009929 (2021).

Download references

Reprints and permissions

Related Articles

Molecular architecture of coronavirus double-membrane vesicle pore complex

Article 14 AUG 24

Long COVID lung damage linked to immune system response

News 18 JUL 24

Vaccines save lives: how can uptake be increased?

Editorial 09 JUL 24

Mpox is spreading rapidly. Here are the questions researchers are racing to answer

News Explainer 28 AUG 24

Mysterious Oropouche virus is spreading: what you should know

News Q&A 26 AUG 24

Birth of protein folds and functions in the virome

Article 26 AUG 24

Tenure-Track/Tenured Faculty Positions

Tenure-Track/Tenured Faculty Positions in the fields of energy and resources.

Suzhou, Jiangsu, China

School of Sustainable Energy and Resources at Nanjing University

ATLAS - Joint PhD Program from BioNTech and TRON with a focus on translational medicine

5 PhD positions for ATLAS, the joint PhD Program from BioNTech and TRON with a focus on translational medicine.

Mainz, Rheinland-Pfalz (DE)

Translational Oncology (TRON) Mainz

Alzheimer's Disease (AD) Researcher/Associate Researcher

Xiaoliang Sunney XIE’s Group is recruiting researchers specializing in Alzheimer's disease (AD).

Beijing, China

Changping Laboratory

Supervisory Bioinformatics Specialist CTG Program Head

The National Library of Medicine (NLM) is a global leader in biomedical informatics and computational health data science and the world’s largest b...

Bethesda, Maryland (US)

National Library of Medicine, National Center for Biotechnology Information

Post Doctoral Research Scientist

Post-Doctoral Research Scientist Position in Human Transplant Immunology at the Columbia Center for Translational Immunology in New York, NY

New York City, New York (US)

Columbia Center for Translational Immunoogy

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Quick links

• Explore articles by subject
• Guide to authors
• Editorial policies

Skip to content

Read the latest news stories about Mailman faculty, research, and events. 

Departments

We integrate an innovative skills-based curriculum, research collaborations, and hands-on field experience to prepare students.

Learn more about our research centers, which focus on critical issues in public health.

Our Faculty

Meet the faculty of the Mailman School of Public Health. 

Become a Student

Life and community, how to apply.

Learn how to apply to the Mailman School of Public Health. 

• Additional Resources

What Is Omicron and How Concerned Should We Be?

Nearly two years after the emergence of the virus that causes COVID-19, a variant of the virus called Omicron is raising concerns around the world. Transmission checked in with some of Columbia Mailman School’s top experts in virology, emerging infectious diseases, epidemiology, and the global response to pandemics to answer questions about the variant, including its potential risks and what we can do to protect ourselves.

What is Omicron?

Omicron (pronounced ah·me·kraan ) is the thirteenth variant of SARS-CoV-2, the coronavirus that causes COVID-19, named by the World Health Organization, using a Greek letter naming scheme. It is the fourth variant designated by the WHO as a “variant of concern” after Delta, which is currently responsible for most cases and deaths around the world. Delta, which is more than twice as contagious as earlier variants, supplanted previous variants in the summer of 2021. So far, scientists do not know whether Omicron is more or less contagious than Delta, but there is sufficient cause for concern.

Where does Omicron come from and Why did it emerge?

In early November, scientists in South Africa identified the variant in a patient with COVID-19 from Botswana, a country that borders South Africa. Subsequently, the variant was detected in South Africa. The identification of new variants is expected. Variants are a natural part of the virus lifecycle and arise as the result of errors (mutations) that take place when the virus copies its genetic code while replicating inside the cells of an infected person.

Why are public health officials concerned?

“While we don’t know yet whether Omicron is more or less contagious than Delta, there are concerns that it may be more contagious because it is rapidly replacing Delta in South Africa,” says W. Ian Lipkin , John Snow Professor of Epidemiology and director of the Center for Infection and Immunity . Another troubling sign: Omicron has many more mutations than earlier variants and these mutations are concentrated in a part of the virus that interacts with human cells—regions that are important for the efficacy of vaccines and treatments. 

Where is Omicron now and Where will it spread next?  

As of November 29, the Omicron variant has been detected in 15 countries. Due to incomplete surveillance and limited availability of virus sequencing around the world, the variant is likely more widespread and will likely be identified in many more countries, including the U.S. However, projecting the future spread of Omicron is not yet possible. “We won’t be able to project its spread and impact until we have a better sense of its transmissibility, its ability to compete with other variants—Delta in particular—its ability to cause breakthrough and repeat infections, and the severity of disease caused by Omicron,” says Jeffrey Shaman , a professor of environmental health sciences who is an expert in infectious disease modeling.

What are the biggest unanswered questions about the new variant and when will we get answers?

The most critical questions about the new variant are whether or not it is more infectious than the Delta variant, whether or not it is likely to cause more severe disease, and whether or not it will compromise the effectiveness of available vaccines or treatments. In laboratory studies, scientists are hard at work examining how well vaccines work against Omicron. Meanwhile, epidemiological studies will determine how infectious the variant is and whether it causes more severe illness. Preliminary answers will likely take a few weeks, according to Jessica Justman , senior director at ICAP at Columbia and associate professor of epidemiology. 

What precautions are being taken against Omicron and why?

Around the world, viral sequences are being examined for the presence of Omicron. Scientists are also working on a vaccine against the new variant, in case one is needed. Meanwhile, countries, including the U.S., have limited visitors from certain southern African countries to slow the arrival of the variant. Some say these restrictions unfairly target southern African countries when evidence already suggests the variant is circulating more widely. Stephen Morse , professor of epidemiology, says restrictions on travel from China in early 2020 did nothing to stop the spread of the virus in the U.S., which instead arrived via Europe. “Travel restrictions alone may buy some time, but I doubt will do much to stop it,” he says.

what else can we do to protect ourselves?

The recommended measures to limit the spread of the virus continue to apply in the face of new variants. As more evidence evolves, experts say we might need to adjust our approaches, but for now, they say it is important to stay the course and use the protective tools we have. The best thing to do is get fully vaccinated, including a booster shot. Additional precautions include avoiding large gatherings, especially indoors, and wearing a mask when indoors, when not with immediate family or small social groups, as well as outdoors in a crowded setting. It is also important to stay home if not feeling well and get tested, as appropriate.

On a policy level, our experts call on improved availability of vaccines around the world, especially in low and middle-income countries, which lag behind wealthy countries in vaccine coverage. “There is an urgent need to produce more vaccine doses and support countries in their vaccination efforts,” says Wafaa El-Sadr , Columbia University Professor and director of ICAP at Columbia. “COVID-19 is everywhere. We must stop transmission, which we know drives the evolution of new variants, and vaccines remain our best tool to stem new infections and the risk of new variants.”

• Share full article

Advertisement

Supported by

Guest Essay

Here’s When We Expect Omicron to Peak

New Covid-19 cases,

United States

By Jeffrey Shaman

Dr. Shaman is an infectious disease modeler and epidemiologist at Columbia. His team built one of the first Covid-19 models.

The Omicron variant is spreading widely and infecting large numbers of people, including the vaccinated and those previously infected with the virus. While spikes in cases have been the norm for the past two years, there are clear indications this wave will differ substantially from previous ones.

The record number of cases in the United States and globally is largely because Omicron is more contagious than other variants and has a greater ability to evade immunity to infection. At the same time, early evidence indicates that it’s less common for people infected with Omicron to experience severe disease and end up in the hospital. This has important implications when estimating just how disruptive Omicron will be in terms of deaths, hospitalizations and work and school interruptions.

To assess the future burden of a variant like Omicron, epidemiologists like myself often turn to mathematical modeling and projection. The idea is to use a computer-based representation of how the virus spreads to simulate potential future outcomes.

It is important for modelers to explore the unknowns around Covid. For instance, evidence indicates that Omicron is more transmissible than the Delta variant, but by how much? By incorporating uncertainties into our models, we don’t merely project a single outcome. Instead, we create a distribution of outcomes, much like the cone of uncertainty used for a hurricane landfall forecast.

Projecting the Covid-19 burden is also more difficult now because of the December holidays. Reporting of cases is often delayed during the two weeks beginning shortly before Christmas until shortly after New Year’s Day. As a consequence, reported case numbers can give the misleading short-term appearance of steep case increases, or even declines.

All these issues create uncertainty and limit how far we can reliably project the burden of Omicron. My inclination is that four to six weeks is as far as modelers should routinely project.

January will likely see a record number of cases

Total new Covid-19 cases by month, United States

25 million total cases

Previous months

Day of the month

This month will likely see a record number of cases

We are having trouble retrieving the article content.

Please enable JavaScript in your browser settings.

Thank you for your patience while we verify access. If you are in Reader mode please exit and  log into  your Times account, or  subscribe  for all of The Times.

Thank you for your patience while we verify access.

Already a subscriber?  Log in .

Want all of The Times?  Subscribe .

• Skip to main content
• Keyboard shortcuts for audio player

Goats and Soda

• Infectious Disease
• Development
• Women & Girls
• Coronavirus FAQ

Omicron is spreading at lightning speed. Scientists are trying to figure out why

A colorized electron micrograph image of a cell (red) infected with with SARS-CoV-2 virus particles (yellow), isolated from a patient sample. Science Source hide caption

A colorized electron micrograph image of a cell (red) infected with with SARS-CoV-2 virus particles (yellow), isolated from a patient sample.

In late November, more than 110 people gathered at a crowded Christmas party at a restaurant in Oslo, Norway. Most of the guests were fully vaccinated. One had returned from South Africa just a few days earlier and was unknowingly carrying the omicron variant of SARS-CoV-2.

Ultimately, about 70% of the partygoers were infected.

Scientists who traced this superspreader event concluded it was evidence that omicron was "highly transmissible" among fully vaccinated adults.

Just over a month later, omicron's speedy worldwide ascent now makes it abundantly clear that the party wasn't an isolated example. In country after country, the new variant has outcompeted its predecessor, the delta variant, with one case of omicron sparking at least three other new infections on average. Cases have soared to record highs in parts of Europe and now the U.S., where about half a million new infections have been recorded in a single day.

"This is a game-changing virus, especially in the vaccinated population where people have had a level of invincibility," says Sumit Chanda , a professor in the Department of Immunology and Microbiology at Scripps Research.

Shots - Health News

With omicron, you need a mask that means business.

Indeed, in a world where vaccinations and infections have built up immunity, other variants were having trouble gaining a foothold. Yet omicron is thriving.

"This changes the calculus for everybody," says Chanda.

And so scientists are trying to figure out: What accounts for omicron's lightning-quick spread?

While it's still early, they're starting to piece together why the new variant is so contagious — and whether that means old assumptions about how to stay safe need to be revamped.

A big question: How does it fare in the air?

So far, omicron's best trick — what helps explain its success more than anything else — is dodging our immunity: the antibodies and other immune defenses put on by the body after vaccination and/or prior infection.

The variant's many mutations on the spike protein allow it to infect human cells more efficiently than previous variants could, leaving many more people again vulnerable. Because of that, "immune escape" alone could be the major reason why the variant looks so contagious compared with delta, which was already highly transmissible.

In fact, omicron has been spreading at a pace that's comparable to how fast the original strain of the coronavirus spread at the very beginning of the pandemic, despite the world's newfound levels of immunity.

"The playing field for the virus right now is quite different than it was in the early days," says Dr. Joshua Schiffer , an infectious disease researcher at Fred Hutchinson Cancer Research Center. "The majority of variants we've seen to date couldn't survive in this immune environment."

Even delta was essentially at a "tie," he says, where it was persisting, but "not growing very rapidly or decreasing very rapidly."

The Coronavirus Crisis

A pediatrician's advice to parents of kids under 5 on omicron, travel and daycare.

A new study from Denmark suggests that much of the variant's dominance comes down to its ability to evade the body's immune defenses.

Researchers compared the spread of omicron and of delta among members of the same household and concluded that omicron is about 2.7 to 3.7 times more infectious than the delta variant among vaccinated and boosted individuals.

But here's an interesting additional point: For unvaccinated people, there was no significant difference in rates of infection between delta and omicron. That would indicate that both variants are about at the same level of transmissibility among the unvaccinated. In other words, under those circumstances, omicron is not necessarily more transmissible than delta.

If confirmed, the findings would support the idea that omicron's increased transmissibility can be ascribed to its "immune evasiveness" — not some other characteristics that make the variant inherently more transmissible, the authors conclude.

This is also what a small study from the University of Maryland may hint at, although here, too, the findings are preliminary and yet to be peer-reviewed.

Researchers measured how much virus that vaccinated people who were infected with omicron were releasing into the air after shouting and singing. Four out of the five were exhaling ample amounts of virus into the air — comparable to the amount shed by unvaccinated people earlier in the pandemic.

"But what's striking is that I was expecting to see the amounts be much higher, and they are not," says Dr. Don Milton , an infectious disease aerobiologist at the University of Maryland School of Public Health, who led the study.

The findings suggest that the spread of omicron could hinge, in part, on the fact that more vaccinated people are contagious and shedding virus, not necessarily that each infected individual is releasing a lot more virus into the air. And if the results hold true, Milton says long-distance transmission is unlikely to become a new concern with omicron, above and beyond what's already been seen with other contagious variants like delta.

"With measles, for example, the source strength is just so intense that even in the next room, people are still at risk of getting infected," he says. "And you don't see much of that with this virus" because it gets so diluted by the time it reaches the next room.

But there is a down side. Says Milton: "The bad news is the vaccine doesn't mean you're not going to transmit it to somebody else."

And he adds that the findings are ultimately limited to those who are vaccinated: "Maybe you get an unvaccinated person, it [the amount of virus] is a whole lot more intense."

Omicron could have other advantages that give it a leg up

With so many mutations, it's still quite possible that omicron does have additional advantages that make it more contagious than other variants — advantages that rely on more than breaking through our prior immunity.

Maybe omicron can produce more copies of itself in a cell? Or maybe it sticks to cells more effectively? Or maybe it's better at hanging in the air and staying infectious?

"Any of those things would make the virus more contagious," says Schiffer of Fred Hutchinson.

It's time to recalculate your COVID 'risk budget.' Here's how

One key difference emerging with omicron is just how quickly someone who gets infected becomes contagious.

Omicron appears to have a shorter incubation period and that can substantially speed up infections across the population. A study of the Oslo Christmas party outbreak found the incubation period could be about three days, compared with 4.3 days for delta and five days for other variants. A small study from CDC also puts the incubation period at about three days.

"That's actually a fairly significant difference," says Schiffer. This would mean there are many more cycles of infections and less time for people who are exposed to take precautions not to expose others.

A mid-December study from Hong Kong has also led scientists to consider that omicron may indeed replicate better in certain cells and therefore have a leg up against delta, at least among the unvaccinated.

Researchers found that omicron multiplied about 70 times faster than delta did in tissue samples from the bronchus — the large airways that lead from the trachea to the lungs. Meanwhile, omicron had much more trouble infecting cells in lung tissue than the original version of the coronavirus that was first identified in Wuhan, China.

"Potentially you could be shedding more virus in your upper respiratory tract than you would be if most of the replication was happening deep in your lungs," says Angie Rasmussen , a virologist at the University of Saskatchewan in Canada.

Like other variants, omicron spreads from the nose and mouth through respiratory droplets at close range and through virus particles that float through the air and can stay suspended for quite awhile, especially in places with poor ventilation.

Rasmussen says this data on faster replication in the bronchus tissue "would suggest you might have more virus in those respiratory secretions, which can come out either as mucus if you have a runny nose or certainly can be exhaled as aerosols and droplets."

Airborne concerns as omicron spreads

If omicron does spread more easily through the air, this faster replication in the bronchus would be one of the two most likely explanations, says Linsey Marr , a professor of engineering at Virginia Tech who studies how viruses transmit in the air. "Infected people are either releasing a lot more virus particles into the air or you can breathe in fewer of them and still become infected — or some combination of those," she says.

While that Hong Kong study focused on what happens in the lab, a cautionary tale of omicron spreading through the air has also emerged from an isolation facility there.

In a report published in early December, Hong Kong scientists describe how a traveler in quarantine at a hotel had infected a person staying across the hallway but never actually had face-to-face contact. "Airborne transmission across the corridor" is the most probable explanation, the authors conclude.

"That suggests a very small amount of the virus was able to cause an infection," says Dr. Michael Klompas , an infectious disease physician and hospital epidemiologist at Brigham and Women's Hospital. This could mean that omicron requires a smaller dose than previous variants to infect people, although there's no data yet to establish whether that is true, he says.

While concerning, such early anecdotes need to be interpreted carefully. There are similar instances of airborne transmission with delta, and hotels and other places repurposed to isolate infected travelers are difficult places to turn into quarantine facilities.

"Can we catch omicron more easily through the air than other variants? I don't think that's known" says Rasmussen. "What is very clear is that you can catch it more easily, period."

A somewhat reassuring point

Despite the many unanswered questions about why omicron is so contagious, scientists say it's important to realize that the coronavirus has not morphed into an entirely new virus.

"The rules haven't changed; it's just the margin for error has got a lot smaller," says Klompas.

When it comes to minimizing your personal risk, the same principles apply: Wear a high-quality mask like an N95, choose outdoors over indoors if possible and avoid large gatherings with unmasked people, especially if they are not vaccinated.

"These risk-reduction measures are additive and you should try to apply as many of them as possible," says Rasmussen .

Even quick face-to-face interactions appear to be more risky with omicron, in part because people have relied on the vaccines as their only layer of defense, says Chanda. "If you walk into a room full of people and someone is infected, the chances have dramatically increased that you will get the virus" — whether you're vaccinated or boosted or not.

Coronavirus FAQ: Remind me, how do you define mild, moderate and severe COVID?

• transmissibility
• omicron variant

An official website of the United States government

The .gov means it’s official. Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

The site is secure. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

• Publications
• Account settings

Preview improvements coming to the PMC website in October 2024. Learn More or Try it out now .

• Advanced Search
• Journal List
• Vaccines (Basel)

A Systematic Review on the Emergence of Omicron Variant and Recent Advancement in Therapies

Beyau m. konyak.

1 Integrated Molecular Diagnostic and Research Laboratory (BSL-2), District Hospital Tuensang, Tuensang 798612, Nagaland, India

Mohan Sharma

Shabnam kharia.

2 Department of Life Sciences, Dibrugarh University, Dibrugarh 786004, Assam, India

Ramendra Pati Pandey

3 Centre for Drug Design Discovery and Development (C4D), Department of Biotechnology & Microbiology SRM University, Delhi-NCR, Rajiv Gandhi Education City, Sonepat 131029, Haryana, India

Chung-Ming Chang

4 Master & Ph.D. Program in Biotechnology Industry, Division of Biotechnology, Chang Gung University, No. 259, Wenhua 1st Rd., Guishan Dist., Taoyuan City 33302, Taiwan

Associated Data

Not applicable.

With the ongoing COVID-19 pandemic, the emergence of the novel Omicron variant in November 2021 has created chaos around the world. Despite mass vaccination, Omicron has spread rapidly, raising concerns around the globe. The Omicron variant has a vast array of mutations, as compared to another variant of concern, with a total of 50 mutations, 30 of which are present on its spike protein alone. These mutations have led to immune escape and more transmissibility compared to other variants, including the Delta variant. A cluster of mutations (H655Y, N679K, and P681H) present in the Omicron spike protein could aid in transmission. Currently, no virus-specific data are available to predict the efficacy of the anti-viral and mAbs drugs. However, two monoclonal antibody drugs, Sotrovimab and Evusheld, are authorized for emergency use in COVID-19 patients. This virus is not fading away soon. The easiest solution and least expensive measure to fight against this pandemic are to follow the appropriate COVID-19 protocols. There is a need to strengthen the level of research for the development of potential vaccines and anti-viral drugs. It is also important to monitor and expand the genomic surveillance to keep track of the emergence of new variants, thus avoiding the spread of new diseases worldwide. This article highlights the emergence of the new SARS-CoV-2 variant of concern, Omicron (B.1.1.529), and the vast number of mutations in its protein. In addition, recent advancements in drugs approved by FDA to treat COVID patients have been listed and focused in this paper.

1. Introduction

The emergence of this ongoing pandemic coronavirus has devastated the world. It has been almost two years since COVID-19 was detected in Wuhan, China. As of 12 August 2022, more than 6 million deaths and 585 million confirmed cases have been reported worldwide, making it one of the deadliest viruses in history [ 1 ]. This virus has undergone several recombination and mutations over the past years, leading to the emergence of a vast array of new variants of concern (VOC) and variants of interest (VOI), resulting in a high level of global health alerts and panic.

While the world has been tackling the Delta variant, the emergence of the novel Omicron variant in December 2021 took the world by storm [ 2 ]. The first SARS-CoV-2 variants to emerge were Alpha, Beta, Gamma, and Delta, and the Omicron (B.1.1.529) variant, classified as VOC by WHO [ 3 ] on 26 November 2021, has become the dominant one in many countries since January 2021 ( Table 1 ). The novel Omicron variant has a larger number of mutations as compared to other VOCs. This has led to a higher rate of infections, higher transmissions, and immune escape from COVID-19 vaccines, resulting in rapid spread worldwide in a shorter period. As per the WHO, this novel variant also enhances immune or diagnostic evasion, causes less severe disease, and shows enhanced transmissibility. In addition, it poses a detrimental impact on epidemiology and shows increased variability in clinical presentation. The four most common symptoms of an Omicron infection, according to the US Centers for Disease Control and Prevention, are cough, fatigue, congestion, and a runny nose [ 4 ]. Although the Omicron variant seems more contagious than previous variants, as per the data available, early findings suggest lower rates of hospitalization for Omicron-positive patients, as compared to the Delta variant. However, the Omicron variant should not be taken lightly. Precautionary measures should be taken such as avoiding crowded spaces, maintaining social distances, and wearing masks to prevent the spread of infection [ 5 ]. The SARS-CoV-2 Interagency Group (SIG) evaluates and classifies the novel variant as a VOC, based on the cases detected in various countries, its travel history, rate of transmission, mutations in the spike protein, and as per data available for other variants. It is also evaluated based on a reduction in the effectiveness of vaccines and monoclonal antibody treatments. The SIG tracks and evaluates the emergence of new viruses and actively monitors the potential impact of vaccines, therapeutics, and diagnostics against SARS-CoV-2 [ 6 ]. This review article highlights the emergence of the Omicron variant, its mechanism, and the vast array of mutations in the spike protein, which enhance transmissibility and immune escape from vaccines. The potential impact on diagnosis, the various advancements in anti-viral drugs, and therapeutic treatments to tackle the ongoing COVID-19 pandemic is also discussed.

WHO-designated SARS-CoV-2 variants of concern (VOCs).

2. The Emergence of the Omicron (B.1.1.529) Variant and Its Sub-Lineage

South Africa was the first country to detect the novel variant of SARS-CoV-2 from specimens collected on 11 November and 14 November 2021. The first Omicron variant was reported to WHO by the South African Department of Health on 24 November 2021 [ 6 ]. On 25 November 2021, the United Kingdom Health Security Agency designated the B.1.1.529 Omicron variant as a Variant Under Monitoring (VUI-21-NOV-01) and, just one day later, it was designated as a VOC by the WHO; the variant was later named Omicron [ 4 , 7 ]. The rapid spread of this variant in South Africa and surrounding countries alarmed the WHO. This could be due to the large number of mutations on the spike protein in the Omicron variant as compared to other VOCs. However, Omicron has been reported to be less severe than the previous variants [ 8 , 9 ]. Three days after the announcement of Omicron on 29 November 2021, by the WHO, this novel variant was detected in Australia, Belgium, Canada, the Czech Republic, Denmark, France, Germany, Italy, Netherlands, and the United Kingdom [ 10 ]. As of 25 December 2021, Omicron had been reported in 108 countries, with nearly 150,000 confirmed cases and 26 deaths, creating an alarming situation worldwide [ 11 ]. The emergence of the Omicron variant in South Africa has also revealed a vaccination gap between the richest and the poorest. Whilst an average of 60% of the population of Europeans has been vaccinated, it is appalling to see that only 5–10% of the African population has been vaccinated [ 12 ]. This could be one of the major factors contributing to the emergence of VOCs. Japan also reported the first two cases of the novel Omicron variant at the end of November 2021 among international travelers returning to the country with the undetected Omicron variant [ 13 ]. India reported the first two cases of the Omicron variant on 3rd December 2021 among international travelers [ 14 ]. In Germany, two suspected cases of the new Omicron variant were first reported on 27 November 2021 and, as the New Year began, this novel Omicron became one of the most dominant variants in Germany, despite protective measures at the initial stage in January 2022 [ 15 , 16 ]. This new variant has been spreading worldwide and has been reported in 180 countries as of 4 February 2022. As of 11 February 2022, the UK reported a maximum number of Omicron cases (422,993) followed by the USA (359,236), Denmark (69,789), Germany (48,866), Canada (30,687), and France (27,487), while an increasing number of cases can be seen on a daily basis in many other countries [ 16 ]. Jansen et al. [ 17 ] reported that the Omicron variant has a shorter incubation period than the previous variants, with similar clinical symptoms. Preliminary data conducted by the National Institute of Infectious Diseases shows a high viral load three to six days after the onset of symptoms [ 18 ].

As the Omicron variant continues to evolve and mutate, new sequences (sub-lineages) of the Omicron variant were reported by the WHO in December 2021, namely: BA.1, BA.2, and BA.3 [ 19 ]. Over the past two months, the BA.1 variant has escalated globally. However, in the last weeks of January 2022, the BA.2 sub-lineage had increased internationally and had already become dominant in Denmark. As of 11 February 2022, BA.2 had been detected in at least 70 countries and 44 U.S. states, according to the data uploaded in GISAID, and a total number of 55,404 sequences in the BA.2 lineage have been detected since the lineage was identified [ 20 , 21 ]. A preprint uploaded in medRxix [ 22 ], concluded that Omicron BA.2 is more dominant and transmissible than the parent Omicron variant (BA.1). It possesses immune-escaped advantages among vaccinated individuals; however, it does not increase its transmissibility to vaccinated individuals with breakthrough infections. India is another country where BA.2 is rapidly replacing the Delta and Omicron BA.1 variants, as per the report [ 23 ]. Data uploaded on GISAID suggest that the BA.2 variant is increasing rapidly in proportion to the original BA.1 variant, thus dominating the parental variant based on the sequence frequency [ 24 ].

3. Mechanism of Omicron Variant

The Omicron variant has the highest number of mutations observed so far, as compared to the other VOCs such as Alpha, Beta, Gamma, and Delta. This variant contains more than 30 mutations in the spike protein, which binds to the ACE2 receptor in the human cell for invasion, and out of which, 15 modifications are observed in a Receptor Binding Domain (RBD), an area strongly associated with humoral immune evasion [ 25 ], thus, increasing its transmissibility and thereby causing the possibility of evading vaccine-induced antibodies [ 26 ]. Researchers from China constructed and studied the binding affinity between the complex structure of the human ACE2 protein and the RBD of the Omicron variant spike protein (S-protein) using atomistic molecular dynamics simulations. They observed that mutations in the RBD of the SARS-CoV-2 Omicron variant resulted in a higher binding affinity to the human ACE2 protein [ 27 ].

There are two distinct mechanisms for the entry of SARS-CoV-2 into a human cell: cell-surface entry and endosomal entry, where TMPRSS2-mediated S protein activation takes place at the plasma membrane and cathepsin-mediated activation takes place in the endolysosome at the cytoplasmic region, respectively [ 28 ]. A researcher from Glasgow University in the UK demonstrated the replication process of different SARS-CoV-2 variants and their mechanisms in entering the human cell. An HIV-pseudotype was evaluated for entry assay. The study reveals that Omicron, like pangolin CoV, uses the endocytosis pathway to enter human cells and is independent of the TMPRSS2 present on the cell surface. This study was further supported by using drug inhibitors targeting either the TMPRSS2 (Camostat) or the cathepsins (E64d). As compared to another variant spike, the Omicron spike shows a reduced syncytium formation, thereby causing fewer lung infections [ 29 ].

4. Mutations in Omicron Variant

In November 2021, Omicron (B.1.1.529) emerged as a VOC. Wahid et al. [ 26 ] had earlier reported the triplet mutation (K417N + E484K + N501Y) in the Beta (B.1.351) and Gamma (P.1) variants, which were highly transmissible, leading to greater COVID-19 hospitalizations, ICU admissions, and even deaths. Such mutations have increased the immune escape potential leading to a decrease in the neutralization of antibodies (such as those found in the Pfizer and Moderna vaccines). The Omicron variant contains overall 50 mutations, with 30 mutations [ 25 ] on the spike protein, which include: A67V, del69/70, T95I, G142D, del143/145, N211I, del212/212, G339D, S371L, S373P, S375F, S477N, T478K, E484A, Q493R, G496S, Q498R, N501Y, Y505H, T547K, D614G, H655Y, N679K, P681H, N764K, D796Y, N856K, Q954H, N969K, and L981F, of which 15 modifications are located at the RBD region [ 30 ]. Cecylia et al. [ 27 ] conducted atomistic molecular dynamics simulations to study the binding interactions between the human ACE2 protein and the RBD of the Omicron spike protein (S-protein). The analysis shows that the Omicron RBD binds more strongly to the human ACE2 protein than does the original Wuhan strain. However, the SARS-CoV-2 Omicron RBD shows weaker binding affinity than the Delta variant [ 31 ]. Most COVID-19 strains contain at least one change from the original Wuhan sequence, D614G, altering the virus’s ability to escape the immune response. The N501Y mutation is present in all VOCs, except the Delta variant [ 32 ]. Interestingly, Omicron’s spike protein mutations, such as D614G, N501Y, and K417N, are found in some other VOCs, thus making the virus more infectious—a prospect that is very concerning.

Similarly, the H655Y, N679K, and P681H mutations in the Omicron spike protein, also found in the Alpha and Delta variants, could increase the transmission of the virus [ 6 , 33 , 34 ]. It has the deletion at spike protein (Δ69–70), position 69–70, similar to the Alpha and Eta variants, that leads to the S-gene dropout or S-gene target failure. This phenomenon may provide a useful proxy to measure the prevalence of the Omicron variant. The rapid transmission of the Omicron variant across the globe could be due to the presence of these larger numbers of mutations in the spike protein, unlike the Delta variant, and thus evading immune response [ 33 ]. However, this phenomenon does not apply to the BA.2 sub-lineage of the Omicron variant, as it does not contain the deletion at S: 69–70 and is S-gene target positive (SGTP) on PCR diagnostic assays [ 35 ]. The comparison and mutual sharing of the spike protein mutations of the Omicron sub-lineages, BA.1, BA.2, and BA.3, are represented by a Venn diagram, as shown in Figure 1 .

Comparison of spike protein mutations of Omicron sub-lineage: BA.1, BA.2, and BA.3. (GISAID: https://www.epicov.org/epi3/frontend#58aca ) (Accessed on 10 February 2022). This Venn diagram represents the common mutation present among the sub-linages of Omicron variant; G142D, T478K, D614G, H655Y N679K, P681H, N764K, D796Y, Q954H, N969K. B.A.1 (30); A67V, del69/70, T95I, G142D, del143/145, N211I, del212/212, G339D, S371L, S373P, S375F, S477N, T478K, E484A, Q493R, G496S, Q498R, N501Y, Y505H, T547K, D614G, H655Y, N679K, P681H, N764K, D796Y, N856K, Q954H, N969K, L981F. B.A.2 (29); T19I, L24S, del25/27, G142D, V213G, G339D, S371F, S373P, S375F, T376A, D405N, R408S, K417N, N440K, S477N, T478K, E484A, Q493R, Q498R, N501Y, Y505H, D614G, H655Y, N679K, P681H, N764K, D796Y, Q954H, N969K. B.A.3 (16); A67V, del69/70, T95I, G142D, del143/145, N211I, del212/212, T478K, D614G, H655Y, N679K, P681H, N764K, D796Y, Q954H, N969K.

The combination of N501Y + Q498R may increase the binding affinity to ACE2, while other substitutions may lead to a decrease in the binding affinity to the ACE2 in the Omicron spike protein. Kinases’, such as PI3K/AKT, signaling are essential in SARS-CoV-2 entry. Based on molecular docking, Bexultan et al. [ 36 ] analyzed the interaction between the potential kinases and the N501Y mutation and observed that the N501Y mutation did not enhance binding to epidermal growth factor receptors (EGFR) due to the mutations. The N501Y mutation-containing lineages might become more infectious since several kinases are elevated in cancer patients. Therefore, additional care for cancer management should be taken into consideration. Mannar et al. [ 37 ] analyzed a cryo-electron microscopy structure between the spike proteins of the Omicron variant in complex with human ACE2. The structure depicts two additional new salt bridges and hydrogen bonds formed by the mutated residues R493, S496, and R498 in the RBD with the ACE2. This enhances other mutations, such as K417N, which is known to reduce the ACE2 binding affinity to the spike protein. These strong interactions at the ACE2 interface may contribute to the rapid spread of the Omicron variant [ 38 ]. Zhuoming et al. [ 39 ] reported that E484K could escape neutralization by convalescent sera, while S477N was resistant to neutralization by multiple mAbs, thus needing further investigation. The increase in binding affinity to the ACE2 receptor by N501Y could aid in an increase in transmission. The combination of N501Y and Q498R may also increase the binding affinity even more; however, other substitutions in the Omicron spike protein are expected to decrease binding to the ACE2. A cluster of mutations (such as H655Y, N679K, P681H) present at the S1–S2 furin cleavage site in the Omicron variant may increase spike cleavage and could aid in transmission. The N679K present at the furin cleavage site adds to the polybasic nature and is associated with an increase in transmission. The P681H mutation (also found in Alpha) enhances spike cleavage, and could also aid in transmission. At this position, an alternate mutation (P681R) is found in Delta [ 40 ]. In India, Surendra et al. [ 41 ] found a major mutation at the P681 position with an R (P681R) similar to the Delta variant (B.167.2) of about 9.71% instead of the H (P681H) mutation. This variant is of considerable public concern, as it is increasing at a high rate in many countries, including the U.S., due to its increased transmissibility and immune evasion. In the nucleocapsid (N) protein region, the Omicron variant also possesses two additional mutations such as R203K and G204R (found in ancestral mutation) that enhance sub-genomic RNA expression and viral RNA binding with key host proteins, thus increasing the viral load [ 42 , 43 ]. Phylogenetic analysis, based on the prevalence of high numbers of mutations, revealed that the Omicron variant is closely related to the Gamma (P.1) variant [ 44 ], and may possess similar characteristics at the molecular level [ 45 ].

5. Impact of Diagnosis on the Omicron Variant

The emergence of mutations in SARS-CoV-2 has resulted in five SARS-CoV-2 variants, namely: the Alpha, Beta, Gamma, Delta, and Omicron variants. The World Health Organization has designated such variants as VOC [ 46 ]. This has resulted in investigating the performance of the potential impact on diagnosis. A rapid diagnostic antigen test is cheap and offers quick results at the point of care when the viral load is high and, hence, provides utility in clinical and public health settings. The rapid test is approved in many countries, including Australia, for self-testing [ 47 ]. However, it is less sensitive than the RT-PCR-based method [ 48 ].

Deerain et al. [ 49 ] evaluated ten commercially available rapid antigen test kits, based on nucleocapsid protein antigens, to check their diagnostic performance (sensitivity) between the Delta and Omicron variants. Overall, they observed no sensitivity difference among the variants. The detection limit of all the kits for the Delta variant was 6.50 log10 copies per mL (Ct 25.4), and 6.39 log10 copies per mL (Ct 25.8) for the Omicron variant. Similarly, Puhach et al. [ 50 ] evaluated seven Ag-RDTs for their sensitivity to the Omicron variant and compared them to other VOCs such as Alpha, Beta, Gamma, and Delta. A trend toward lower sensitivity for Omicron detection compared to the other VOCs was observed. As per the data retrieved on 28 December 2021 (the Food and Drug Administration), it suggests that the antigen test provides a rapid result, and does detect the Omicron variant, but is not a very reliable or sensitive diagnostic testing option [ 51 ].

The Paul Ehrlich Institute (PEI) has also investigated and evaluated the sensitivity of 198 rapid antigen tests (Qualitative Lateral Flow Tests) using uniform sample material marketed in Germany until the end of January 2022. The current state-of-the-art was defined as corresponding to a minimum sensitivity of 75% for the pools with Cq ≤ 25. However, the results do not allow any conclusions regarding the specificity of the tests [ 52 ]. Some studies have also demonstrated that up to 50% of the positive cases detected by rapid tests are false positives as compared to PCR diagnostics tests. A recent small preprint study that has not been peer-reviewed found that the antigen test fails to detect the virus on day zero of 30 individuals who turn out to be COVID positive in the PCR test. The PCR tests also indicated a higher viral load [ 53 ]. However, a study performed in January 2022, in California, on 731 individuals’ shows that the Abbott BinaxNOW rapid tests could detect the Omicron variant, as they did with other variants, especially when people have higher viral load and were symptomatic [ 54 ]. The Abbott BinaxNOW Rapid Antigen Test can be a useful adjunct to RT-PCR testing for the detection of SARS-CoV-2 infections [ 55 ].

The RT-PCR test is considered to be the ‘gold standard’ for detecting coronavirus. In the RT-PCR, two or more spike genes are targeted; therefore, there are chances to detect one of the genes in case of any mutations, thus highlighting its advantage for the Omicron variant. Ever since the detection of SARS-CoV-2 in 2019, it has undergone a broad process of replication and mutation in the spike proteins and RBD, generating a vast number of VOIs and VOCs. Due to this mutation, a phenomenon called ‘S-gene dropout’ or ‘S-gene target failure’ has been reported [ 7 ]. This vast mutation has jeopardized the reliability of currently used diagnostic kits for detecting SARS-CoV-2 and, hence, requires a regular re-evaluation of commercially available kits based on the emerging VOIs and VOCs [ 56 ]. ‘S-gene target failure’ has been suggested as a marker in identifying the Omicron variant. However, with the emergence of the new BA.2 sub-lineage of Omicron (which does not contain 69/70del in the spike protein), it cannot be considered as a marker for the presence of Omicron and requires confirmation of Omicron by sequencing [ 4 ]. This phenomenon has been supported by Metzger et al. [ 57 ], who obtained a piece of information and collected 39 assays of the most commonly used PCR tests in Switzerland and Liechtenstein, targeting genomic loci such as the ORF1ab region, the RdRp gene, the S gene, the E gene, the N gene, and the M gene. Only two assays showed S-gene dropout for Omicron out of eight assays targeting the S gene. Hence, gene sequencing data analysis is required to confirm the presence of the Omicron variant.

Whole-genome sequencing of Omicron with next-generation sequencing (NGS) might serve as a gold standard to detect SARS-CoV-2 variants despite being time-consuming and costly. It also requires large data processing. Fu et al. [ 58 ] compared and evaluated the Allplex SARS-CoV-2 Master Assay and Variants I Assay (a direct PCR-based variant analysis) to detect HV69/70 deletion, Y144 deletion, E484K, N501Y, and P681H spike mutations with NGS for 115 samples and observed sensitivity of 98.7% with the Master Assay and 100% with the Variants I Assay. These assays can be utilized as useful tools to rapidly monitor selected and updated VOCs in resource-limited settings. Currently, the CDC is working to understand the new Omicron variant and the effectiveness of commercially available diagnostic tools and authorized medical countermeasures, such as vaccines and therapeutics, against this variant, and is providing technical support to monitor the epidemiologic and clinical features of novel variants [ 59 ].

6. Advancement in Therapeutics Drugs

The emergence of COVID-19 has led to the development of various repurposed and therapeutic drugs, including antivirals and antibody drugs. The U.S. Food and Drug Administration (FDA) have authorized the use of these drugs for emergency purposes in COVID-19 patients with serious illnesses, as per the panel’s recommendation. Meanwhile many anti-viral drugs and mAbs are under investigation.

The in vitro studies performed by IGM Biosciences, Inc. indicate the novel antibody IGM-6268 exhibits potential neutralizing activity against the Omicron variant and all other VOCs and VOIs [ 60 ]. Some of the recent advances in therapies that have been approved and authorized for emergency use in COVID-19 patients and are suitable for the Omicron variant are being discussed in this section ( Table 2 ).

List of drugs which has been approved and authorized by FDA for emergency use in COVID-19 patients. (Source: FDA homepage, Medlineplus, Medicalletter).

6.1. Immunomodulatory Drugs

Amid Omicron, WHO continues to approve new COVID-19 treatments for hospitalized patients, according to their disease severity. The arthritis drugs tocilizumab and sarilumab [ 61 , 62 ], which have been found to have efficacy in the treatment of COVID-19 patients with moderate to severe COVID-19 pneumonia, have recently been approved by WHO [ 63 ]. Similarly, dexamethasone, which is effective at reining in lung-damaging inflammation [ 64 ], and Baricitinib a Janus kinase (JAK) inhibitor, are also approved by WHO for treatment in COVID-19 patients as per the panel’s recommendation [ 65 ]. Recently, studies have shown that dextromethorphan treatment was characterized by regulation of adaptive immunity and other specific local innate; however, it was not associated with the regulation of pro-inflammatory pathways in COVID-19 acute respiratory distress syndrome (CARDS) [ 66 ].

6.2. Antivirals Therapy

Recently, the U.S. FDA issued an emergency use authorization (EUA) for Pfizer’s Paxlovid (nirmatrelvir tablets and ritonavir tablets) for the treatment of COVID-19 patients with mild–moderate symptoms and those at high risk of progressing into severe illness. This should be prescribed immediately, within five days after diagnosis of COVID-19 [ 67 ]. During the biochemical assay, the nirmatrelvir drug was shown to inhibit the 3CL protease associated with the Omicron (B.1.1.529) variant [ 68 ]. In vitro studies also suggest that Paxlovid has the potential to maintain plasma concentrations, thus preventing Omicron and other variants from replicating.

Molnupiravir, an oral antiviral drug, is a small molecule of the synthetic nucleoside derivative N-hydroxycytidine (NHC). It targets viral RNA polymerase and inhibits SARS-CoV-2 replication. It was granted EUA by the FDA’s Antimicrobial Drugs Advisory Committee on 23 December 2021, for the treatment of COVID-19 [ 69 ].

The antiviral drug Veklury (remdesivir) was approved by the FDA in 2020 for the treatment of COVID-19 in adult and pediatric patients, and those of old age [ 70 ]. These three drugs: molnupiravir, remdesivir, and paxlovid have shown neutralizing activity against other VOCs, including the novel Omicron variant [ 71 ]. Many antiviral drugs such as Ivermectin, Interferon Alfa, Interferon Beta, Interferon Lambda, and Nitazoxanide are still under evaluation for the treatment of COVID-19. All these drugs have paved the way as new hopes to fight against the COVID-19 pandemic.

6.3. Monoclonal Antibodies

The emergence of COVID-19 has led to the development of various treatments. Monoclonal antibodies (mAbs) are a novel class of antiviral intervention [ 72 ]; they target the RBD of the SARS-CoV-2 spike protein, which is highly mutated in the Omicron variant [ 73 ]. They are one of the most effective therapeutic strategies to neutralize viral replication. This has been shown proven in a previous experiment conducted by researchers from the Baylor University Medical Centre, Dallas, Texas in the US, where dual mAb therapy was shown to reduce viral transmission [ 74 ].

Currently, four anti-SARS-CoV-2 mAb products: bamlanivimab plus etesevimab, casirivimab plus imdevimab (REGEN-COV), sotrovimab, and tixagevimab plus cilgavimab (Evusheld) have been authorized by the FDA for emergency used to treat COVID-19-positive, non-hospitalized patients who are likely to develop more serious disease at the later stage [ 75 ]. The bebtelovimab monoclonal antibody was approved recently [ 76 ]. Such mAbs as casirivimab plus imdevimab, and bamlanivimab plus etesevimab, which have shown effectiveness in the previous VOCs, have reduced neutralization in the Omicron variant [ 77 ].

Recently, Emi et al. [ 78 ] assessed the neutralizing activities of mAbs using a live-virus focus reduction neutralization assay (FRNT) against the Omicron variant and other VOCs. Etesevimab, bamlanivimab and imdevimab did not neutralize Omicron. Casirivimab showed reduced neutralization against the Omicron variant. COV2-2196 (tixagevimab), COV2-2130 (cilgavimab), and S309 (marketed as sotrovimab) retained neutralizing activity against the Omicron variant. Thus, there are two authorized monoclonal antibody treatments against Omicron—Sotrovimab and Evusheld. Early reports also suggest that bamlanivimab and C144-LS antibodies have reduced efficacy against the Omicron variant. Based on early modeling, studies have shown casirivimab plus imdevimab (REGN-COV2), as well as the Rockefeller University antibody C135, to be effective against the Omicron variant [ 79 ]. Some of the monoclonal antibodies authorized by the FDA for emergency use are listed below.

6.3.1. Bamlanivimab and Etesevimab

These mAbs bind at the overlapping sites in the spike protein RBD of SARS-CoV-2; blocking its attachment to the human ACE2 receptor. The FDA has banned the use of these mAbs in some areas of the United State due to the progression of variant resistance [ 80 ]. However, the FDA has approved a EUA to allow the use of this mAbs injection in certain non-hospitalized adults and children and infants (≥2 years of age) who have mild to moderate COVID-19 symptoms with a risk of progressing to serious illness [ 81 ].

6.3.2. Casirivimab and Imdevimab mAb

These are recombinant human mAbs that prevent the entry of the virus into human cell by targeting the spike protein of SARS-CoV-2. The FDA has authorized the use of these mAbs to treat mild to moderate SARS-CoV-2-positive adults and pediatric patients. It is also administered to patients above 65 years of age with chronic medical conditions. However, it is not authorized for hospitalized COVID-19 patients with oxygen therapy [ 82 ]. Recently, the FDA rescinded its authorization of these drugs, due to the prevalence of the Omicron variant [ 83 ].

6.3.3. Sotrovimab

This mAb targets an epitope region in the spike protein RBD that is conserved between SARS-CoV and SARS-CoV-2. This monoclonal antibody has been shown to neutralize the Omicron variant. However, it is not authorized for use in COVID-19 patients who are hospitalized with mechanical ventilation [ 84 ].

6.3.4. Tixagevimab Plus Cilgavimab

The tixagevimab and cilgavimab monoclonal antibodies bind to non-overlapping sites of the SARS-CoV-2 spike protein, preventing the interaction between the virus and the ACE2 receptor. The FDA has approved a EUA to allow certain adults and children 12 years of age and older to receive this mAbs injection. The combination has shown to somewhat decrease neutralizing activity in in vitro against the Omicron variant [ 85 ].

6.3.5. Bebtelovimab (LY-CoV1404)

This mAbs has not been approved and has only been authorized for emergency use by the FDA for treatment of mild to moderate COVID-19 patients (≥12 years old) with a high risk of progressing to severe illness. It neutralizes the SARS-CoV-2 spike glycoprotein RBD, thereby inhibiting the entry of the virus into a human cell. Bebtelovimab is active and has shown some neutralizing activity against other VOCs, including the Omicron variant [ 76 ].

Thus, the abilities of all these monoclonal antibodies and anti-viral therapies to fight and neutralize the Alpha, Beta, Gamma, and Delta VOCs—including the novel Omicron variant—have paved the way for hope in the future to make a potential therapeutic and diagnostic intervention.

7. Discussion

The emergence of the novel Omicron variant has created chaos worldwide. Just after the announcement of Omicron as a VOC by WHO, this novel variant had already spread globally. This rapid spread of the Omicron variant has concerned global health bodies. This is due to a high level of mutation; overall, Omicron has 50 mutations, with 30 mutations on its spike protein. This review gives an overview, highlighting concerns about the emergence of the Omicron variant, its vast array of mutations, the impact of diagnosis methods to detect the novel Omicron variant, and the novel advancement in therapeutic drugs.

The Omicron variant possesses a phenomenon called S-gene dropout, due to the deletion of the amino acid at spike protein position 69–70. This acts as a marker to measure the prevalence of the Omicron variant during diagnosis. However, this phenomenon does not apply to the BA.2 sub-lineage of the Omicron variant. A vast number of mutation and phylogenetic analyses revealed that the Omicron variant may possess similar characteristics to the Gamma (P.1) variant at the molecular level, predicting that drugs suitable for gamma may equally work for the novel Omicron variant.

Recent in vitro studies indicate that Novel Antibody IGM-6268 exhibits potential neutralizing activity against the Omicron variant, as well as other VOCs and VOIs. Interestingly, three drugs namely: molnupiravir, remdesivir, and paxlovid have been approved and authorized by the FDA for emergency use, as they show neutralizing activity against other VOCs, including the novel Omicron variant. This article has a limitation, as it lacks clinical data on the efficacy of mAbs and anti-viral drugs for the treatment of patients with the Omicron variant. Here, we have only described mAbs and anti-viral drugs authorized by the FDA for emergency use in hospitalized and non-hospitalized COVID-19 patients.

It is almost inescapable that there will be the emergence of a new variant, as long as there is a loophole in one part of the world that is unprotected.

8. Conclusions and Prospect

It has been more than two years since the emergence of this COVID-19 pandemic. Despite several measures and protocols to control the virus, it has dominated the world. High levels of effort and mass vaccination campaigns to restrain the spread of this virus have become useless with the emergence of novel variants. COVID-19 has escalated around the globe within a short period and the outcome is devastating, with global health concerns and economic fallout. The emergence of a new VOC every year with the accumulation of a large number of mutations is of concern. The vast array of mutations in SARS-CoV-2 has recently given rise to the most mutated Omicron variant of SARS-CoV-2. The emergence of mutations could be due to the transmissibility of the virus from person to person, leading to its escape from population immunity and frequent transmission. It is the nature of the virus to mutate. This novel Omicron variant has shown itself to be resistant to vaccination and requires booster doses. The hypothesis of its epizootic transfer needs validation and should be thoroughly investigated. At present, there is no specific data and evidence to get rid of SARS-CoV-2. Moreover, the etiology of SARS-CoV-2 is poorly understood. As of now, some anti-viral and monoclonal antibody drugs are being authorized by the FDA for emergency use, as per the panel’s recommendation. This COVID-19 is not going away soon, and may remain forever. The only way to tackle this situation is to follow appropriate protocol and measurements as per the WHO recommendations, such as quarantine, keeping good personal hygiene, social distancing, wearing a mask, and vaccination. In addition, strengthening the level of research for the development of potential vaccines and anti-viral drugs, and a proper strategy to tackle the situation in case of new variants should be evaluated at the global level. It is also very important to monitor and expand genomic surveillance to keep track of the emergence of new variants, thus avoiding the spread of new diseases worldwide.

Funding Statement

This research was funded by two industry–academia collaboration projects, VtR Inc-CGU, R.O.C., project grant (SCRPD1L0221), DOXABIO-CGU, R.O.C., project grant (SCRPD1K0131), and also the CGU project grant (UZRPD1L0011).

Author Contributions

Conceptualization, B.M.K., R.P.P. and C.-M.C.; methodology, B.M.K. and S.K.; validation, R.P.P.; formal analysis, B.M.K. and M.S.; investigation, B.M.K., M.S., S.K. and R.P.P.; resources, B.M.K. and S.K.; data curation, B.M.K.; writing—original draft preparation, B.M.K.; writing—review and editing, B.M.K., M.S., S.K., R.P.P. and C.-M.C.; visualization, B.M.K.; supervision, R.P.P. and C.-M.C.; project administration, R.P.P.; funding acquisition, C.-M.C. All authors have read and agreed to the published version of the manuscript.

Institutional Review Board Statement

Informed consent statement, data availability statement, conflicts of interest.

The authors declare no conflict of interest.

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

• Coronavirus

The COVID-19 Omicron Variant

What Is the Omicron Variant? 

In November 2021, the World Health Organization (WHO) first identified the Omicron mutation of the COVID-19 virus as a variant of concern. It quickly became the most common strain worldwide.

Since then, several sub-variants of Omicron have surfaced, including BA.2, BA.3, BA.4, and BA.5. By the summer of 2022, the BA.5 variant was the most dominant strain in the US. The BA.5 and BA.4 variants appear to be the most contagious types of COVID-19 so far, according to the CDC. In January of 2023, a new Omicron variant called XBB.1.16 was reported and labeled as “one to watch” by the WHO.

Omicron variants seem to cause less serious illness than earlier types of this coronavirus. The COVID-19 vaccines still work well to protect people against hospitalization and death. Th e new bivalent vaccine targets both the original strain as well as Omicron.

Who's at Risk for the Omicron Variant?

Your chances of getting any variant of COVID-19 are greatest if you haven't gotten the COVID-19 vaccine. It's still possible to get the virus if you've been vaccinated (breakthrough infection), but your symptoms should be milder and your chances of having to go to the hospital are much less.

Several other things raise your risk of getting very sick from COVID-19, including

• A weakened immune system
• Other health conditions, such as obesity, diabetes, heart failure
• Smoking, whether currently or in the past

Omicron Symptoms

Early studies found that cold-like symptoms were common in those with Omicron. They reported that the top five symptoms related to the variant were:

• Mild or severe fatigue
• Sore throat

But other common COVID-19 symptoms, such as cough, fever, and loss of smell or taste, are still important signs to watch out for in case of any COVID-19 variant.

WHO experts have said there isn’t any data that suggests Omicron causes symptoms that are different from the ones produced by other COVID-19 variants.

Omicron symptoms day by day

A 2020 study from the University of Southern California found that COVID-19 symptoms tend to come in this order:

• Muscle pain and headache
• Nausea and vomiting

If your symptoms follow this pattern, you may want to take a COVID-19 test , seek care, and begin to self-isolate.

How long do you stay contagious with Omicron?

This variant has a shorter incubation time than those that came before it — about 3 days. If you have it, you can spread the virus to others from 1-2 days before your symptoms start until 2-3 days after they've cleared up. Even if you never show symptoms, you can still be contagious. Ten days after your symptoms begin or you test positive for COVID-19, you should no longer be contagious, as long as you're feeling better and your fever has stopped.

Omicron Incubation Period

Studies show that the incubation period for Omicron is 3.42 days. This is shorter than the ones for the Alpha, Beta, and Delta variants.

How Severe Is Omicron?

Omicron typically causes less severe disease than other variants. However, some people may still get very sick, need to be hospitalized, and could die from an Omicron infection.

Having a less severe case of COVID-19 is especially true for instances of reinfection or breakthrough cases in people who are fully vaccinated. One early study shows that a previous infection only gives a 19% protection rate. It puts the chances of getting reinfected at almost 5½ times higher with this variant than with the Delta variant .

Remember that even a relatively mild case of COVID-19 can cause long COVID: symptoms that last weeks or months after the first illness has passed.

How Quickly Does Omicron Spread?

Omicron spreads more easily than earlier variants of COVID-19, including Delta. Researchers think this is mostly because this strain is better able to get around people's immune defenses, even if they've been vaccinated.

What Do We Know About Omicron Subvariants?

Omicron BA.2 or “ stealth ” subvariant. Scientists named this variant Omicron BA.2 to distinguish it from the original Omicron variant, BA.1. At first, scientists thought BA.2 wasn’t as contagious as BA.1 and would fade away soon. That didn’t happen. Starting in January 2022, BA.2 appeared to be at least as easy to transmit as BA.1.

A January 2022 study in Denmark showed no difference in the number of hospitalizations caused by BA.2 and BA.1. It also showed that as BA.2 cases went up, BA.1 cases went down. But other countries (Great Britain, Norway, and Sweden) reported a slower increase in the number of BA.2 cases.

Early studies show that current vaccines and boosters seem to work at least against this variant, protecting against a first infection as well as against serious illness.

BA.4 subvariant. Experts first detected the BA.4 subvariant in South Africa in early 2022, followed shortly by the BA.5 subvariant. Since then, the number of countries and cases linked to these variants has spiked.

Both BA.4 and BA.5 have mutations that make them different from previous Omicron subvariants. These mutations affect the "spike" proteins that help the virus latch onto and infect your cells. This makes infection easier. It also helps BA.4 and BA.5 evade virus-fighting antibodies from previous infections with COVID-19.

BA.5 subvariant. BA.5 seems to spread more easily than BA.4. In late July 2022, BA.5 was responsible for about 78% of COVID cases in the U.S., compared to 13% for BA.4. Along with the spike protein mutation, BA.5 has additional mutations that distinguish it from BA.4.

Experts believe that symptoms of BA.4 and BA.5 are similar to those of past variants. They include:

• Constant cough

XBB subvariant. This subvariant is a combination of two BA.2 strains. It has mutations that help it evade immunity better than other variants. It also attaches more tightly to cells, making it easier to spread. It arose in mid-2022 and quickly became the cause of a majority of COVID-19 cases in the U.S. But it didn't cause a big jump in the number of cases. Because it has so many mutations, you could easily be reinfected with this one if you already had COVID-19 caused by another strain of the virus.

EG.5 or “ Eris ” subvariant. This descendant of the XBB subvariant first appeared in February of 2023. And by August of that year, it had become the most common and fastest-spreading subvariant in the U.S. While it spreads rapidly, experts have found that it's not more severe than strains that came before it.

How Do Doctors Diagnose Omicron?

To find out if you have the virus , you’ll need to take a COVID-19 test. You can access at-home tests or see a doctor to get one. If you test positive, more testing would be needed to tell if your case was caused by this variant. But this process takes a long time and is expensive. Experts don’t usually do it for each positive COVID-19 case. The tests are also done anonymously to protect people’s privacy, so you won’t get that information.

How Do Doctors Treat Omicron?

Researchers continue to look at how well current COVID-19 treatments help with Omicron cases. Because of the genetic changes in this variant, some treatments will continue to be effective, while others may be less useful. Your doctor may suggest antiviral medicines or monoclonal antibody treatments as an outpatient depending on your risk factors for serious disease from COVID-19.

Corticosteroids and IL6 receptor blockers still help people with severe COVID-19 infections.

How long does Omicron last?

This variant has an incubation period of just over 3 days. If you have Omicron or any variant of COVID-19, you will likely have symptoms for a couple of weeks. You're contagious from 1-2 days before your symptoms start until 2-3 days after they're gone. You can be contagious even if you don't have symptoms. You shouldn't be contagious anymore about 10 days after you first have symptoms or a positive COVID-19 test, as long as you're not having symptoms or a fever .

Does the COVID-19 Vaccine Protect Against Omicron?

The BA.4 and BA.5 variants are close enough to the original Omicron virus, and existing COVID-19 vaccines help prevent serious illness. So, it's important to get your COVID-19 vaccine and boosters.

The new bivalent booster vaccine targets both the original strain as well as Omicron.

Omicron booster

In October of 2022, the FDA authorized updated booster COVID-19 vaccines. These are bivalent vaccines, which means that they target both the original strain of the virus and the Omicron BA subvariants. You get this booster as a single dose.

If you’re an adult, you can get your booster as soon as 2 months after your most recent COVID-19 vaccine. But to get the maximum benefit, it’s best to wait at least 6 months when the antibody levels from your vaccine have gone down. If you’ve had COVID-19 recently, wait for 3 months from the date you first had symptoms or your positive test result if you didn’t have symptoms.

You can get the booster at the same time as any other vaccines you may need, including the flu vaccine. 

Visit the CDC website to see current booster recommendations for people aged 65 and older, children between the ages of 6 months and 5 years, and those with weakened immune systems .

When you get your booster, you may have side effects that include:

• Soreness at the site of injection
• Slight fever or chills

These side effects are likely to be mild and should go away within a few days.

How Can You Prevent Omicron?

There are many things you can do to protect yourself against Omicron and other COVID-19 variants:

Get vaccinated. Vaccines are still the best public health step to protect people against serious illness from COVID-19. Get boosters if you're eligible.

Wear a high-quality mask.  Your mask will protect you and those around you from all variants. The CDC suggests that you wear a mask in public indoor areas, regardless of whether you’ve had the COVID-19 vaccine, if the COVID-19 community level is high, or if you prefer to be masked. Also, wear a mask if you or a family member are at high risk for severe COVID-19 disease even if the community level is at medium.

Social distance.  It’s important to continue to social distance to stop the spread of any variant of COVID-19 when there is a threat in the area.

Get a test. Self-tests or tests given by medical professionals can tell you if you have COVID-19 or not. These tools can help you take steps to protect others from Omicron and other variants.

Other safety measures. Open your windows to improve ventilation, keep your hands clean, stay away from crowded or poorly ventilated areas, and cough or sneeze into your elbow or a tissue.

Omicron is a variant of SARS-CoV-2, the virus that causes COVID-19.

• It first appeared in November 2021 and quickly became the dominant variant around the world.
• It spreads faster than previous COVID-19 variants but causes less severe illness.
• Its symptoms are similar to those of other variants of this virus.
• The currently available bivalent booster vaccines target Omicron subvariants.
• To protect yourself from Omicron, get the COVID-19 vaccine and boosters, wear a high-quality mask, and practice social distancing in high-risk situations.

Omicron FAQs

What is Omicron?

Omicron is a variant of SARS-CoV-2 , the virus that causes COVID-19. A short time after it was identified, it became the dominant variant around the world.

Is Omicron a mutation?

All viruses mutate (or change) over time. Some of these changes don't alter the virus much. But others affect how they operate: They may help them adapt to the immune defenses of their host organisms so they can continue to spread. Or they can make the illness they cause more severe or harder to treat. The virus that causes COVID-19 has mutated several times since it first appeared. This means that there are several different variations or lineages that people can catch and spread to others.

Why is Omicron serious?

The incubation period for this variation of the virus is very short. You're contagious as soon as the day after you've been infected and before you have any symptoms. This makes it easy for someone to spread the illness to many other people very quickly before they realize they're sick and start to isolate themselves.

When did Omicron start?

The Omicron variation was first identified in late November 2021. The first case in the U.S. was confirmed one week later.

Top doctors in ,

Find more top doctors on, related links.

• Coronavirus News
• Coronavirus Reference
• Coronavirus Features
• Coronavirus Slideshows
• Coronavirus Videos
• Cold, Flu & Cough
• Cystic Fibrosis
• Lung Cancer
• Pulmonary Hypertension
• Quit-Smoking Assessment
• Smoking Cessation
• Tuberculosis
• Tuberous Sclerosis

• All health topics

Popular topics

• Communicable Diseases Department
• Vaccine preventable disease
• Department of Healthier Populations and Noncommunicable Diseases (HPN)
• Universal health coverage
• Research and Innovation
• Planning, Monitoring and Evaluation
• Publications
• News releases
• Media Statements
• Feature stories
• Opinion Editorials
• World Health Day 2024
• Emergency Operations
• Country Health Emergency Preparedness & IHR
• Infectious Hazard Management
• Health Emergency Information & Risk Assessment
• Public health Laboratory services
• Regional Strategic Roadmap for Health Security (2023-2027) endorsed by the Regional Committee
• Nepal Earthquake
• Thailand becomes first in SEAR with WHO classified emergency medical team
• Where we work
• Country Strategy and Support
• Regional Director
• Regional Committee
• Seventy-sixth Session of the Regional Committee
• Collaborating Centers

Take all measures to prevent further spread of Omicron – WHO

SEAR/PR/ 1777

New Delhi, 18 December 2021 –  

With seven countries in South-East Asia Region confirming cases of the new COVID-19 variant Omicron, the World Health Organization today emphasized on urgent scale up of public health and social measures to curtail its further spread.

“Countries can – and must – prevent the spread of Omicron with the proven health and social measures.  Our focus must continue to be to protect the least protected and those at high risk,” said Dr Poonam Khetrapal Singh, Regional Director, WHO South-East Asia Region.

The overall threat posed by Omicron largely depends on three key questions – its transmissibility; how well the vaccines and prior SARS-CoV-2 infection protect against  it, and how virulent the variant is as compared to other variants.

From what we know so far, Omicron appears to spread faster than the Delta variant which has been attributed to the surge in cases across the world in the last several months, the Regional Director said.

Emerging data from South Africa suggests increased risk of re-infection with Omicron, she said, adding that there is still limited data on the clinical severity associated with Omicron. Further information is needed to fully understand the clinical picture of those infected with Omicron. We expect more information in the coming weeks.

Omicron should not be dismissed as mild, the Regional Director said, adding that even if it does cause less severe disease, the sheer number of cases could once again overwhelm health systems. Hence, health care capacity including ICU beds, oxygen availability, adequate health care staff and surge capacity need to be reviewed and strengthened at all levels. 

“We must continue to do it all. Protect yourself and protect each other. Get vaccinated, wear a mask, keep a distance, open windows, clean your hands and cough and sneeze safely. Continue to take all precautions even after taking vaccine doses,” the Regional Director said.

On the impact of the new variant on vaccines, Dr Khetrapal Singh said preliminary data suggests that that vaccines may likely have reduced effectiveness against infections by the Omicron variant. However, studies are underway to better understand the extent to which Omicron may evade vaccine and/or infection derived immunity and the extent to which current vaccines continue to protect against severe disease and death associated with Omicron. Globally, the pandemic is driven by the Delta variant, against which the vaccines continue to provide a robust level of protection from severe disease, hospitalization, and death. Hence, our efforts to scale-up vaccination coverage must continue.

“Vaccines are an important tool in our fight against the pandemic, but, as we know,  vaccines alone will not get any country out of this pandemic. We must scale up vaccination and at the same time implement public health and social measures, which  have proven critical to limiting transmission of COVID-19 and reducing deaths,” the Regional Director said.

Public health and social measures include surveillance and response such as testing, genetic sequencing, contact tracing, isolation, and quarantine. They include personal protective measures such as masks; physical distancing; avoiding crowded, closed and confined settings; ensuring hand hygiene and respiratory etiquette. Physical distancing measures include regulating the number and flow of people attending gatherings, maintaining distance in public or workplaces.

WHO has been advocating for the measures to be tailored to local settings and conditions, and implemented in a timely manner to be effective. 

Media Contacts

Shamila Sharma

Public Information and Advocacy Officer WHO South-East Asia Regional Office