omicron essay in english pdf

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• 02 December 2021
• Correction 07 December 2021

How bad is Omicron? What scientists know so far

• Ewen Callaway &
• Heidi Ledford

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Barely a week has elapsed since scientists in Botswana and South Africa alerted the world to a fast-spreading SARS-CoV-2 variant now known as Omicron . Researchers worldwide are racing to understand the threat that the variant — now confirmed in more than 20 countries — poses to the world. Yet it might take scientists weeks to paint a more complete picture of Omicron, and to gain an understanding of its transmissibility and severity, as well as its potential to evade vaccines and cause reinfections.

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Nature 600 , 197-199 (2021)

doi: https://doi.org/10.1038/d41586-021-03614-z

Updates & Corrections

Correction 07 December 2021 : An earlier version of this story misspelt Richard Lessells’ name.

Pulliam, J. R. C. et al. Preprint at medRxiv https://doi.org/10.1101/2021.11.11.21266068 (2021).

Schmidt, F. et al. Nature https://doi.org/10.1038/s41586-021-04005-0 (2021).

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Omicron: A New Rise to Epidemic

Journal of Pharmaceutical Research International

The world has been suffering for the past two and half years since the emergence of the plague Covid-19, which has caused more than 5.57 million deaths globally. The new coronavirus Omicron variants following alpha, beta, gamma, and delta continue to spread. The virus, which was first detected in Botswana and South Africa in November, has since surged globally in the past few weeks, faster than any previously known variant of the coronavirus. Omicron has proven to be highly contagious and less receptive to vaccines compared with other variants. The aim of this study was to provide a brief outline of what we already know about the Omicron virus and what needs to be learned about the different variants of this kind.

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Coronavirus was first originated in the city of Wuhan, China, in late 2019 however the flare-up spread rapidly across the globe in the primary long stretches of 2020. It was announced a worldwide pandemic by the WHO on 11 March 2020. WHO's present approaches and defends are as yet viable against viral strains found since the episode started. The Delta variety of the Covid, which causes COVID-19, causes a greater number of diseases and spreads speedier than prior variations of the infection. The Delta variation is profoundly infectious, over 2x as infectious as past variations. On November 24, 2021, another variation of COVID-19, B.1.1.529, was accounted for to the planet Health Organization (WHO). On November 26, 2021, WHO named the B.1.1.529 Omicron and arranged it as a Variant of Concern (VOC). The Omicron variation probably will spread more effectively than the primary SARS-CoV-2 infection and the way effectively Omicron spreads contrasted with Delta stays obscure. Acute Cor...

Sunita Vagha

SARS is a type of acute respiratory syndrome. Coronavirus 2 (SARSCoV2), highly contagious, affecting people worldwide. Coronavirus Disease 19 (COVID19) leads to a rapidly spreading respiratory distress syndrome. It has caused a global pandemic and severe health crisis in most countries. Due to its continual evolution, further research into the virus's pathogenicity and virulence mechanisms and the development of efficient therapy techniques are urgently required. The current paper summarises what is known about the virus's evolutionary and structural features to comprehend better its mutational pattern and probable role in the current pandemic. In December 2019, the Coronavirus Disease (SARSCoV2) began a destructive path toward a global pandemic in Wuhan, China. Since then, several SARS CoV2 variants have been discovered. Despite the speedy development of a COVID19 vaccine and ongoing mass vaccination efforts around the globe, the discovery of the latest SARSCoV2 variants co...

Dr. Chandra Mohan

In 2019, human race again came across a highly transmittable and pathogenic viral infection viz. COVID-19 and along with its pandemic nature, caused severe acute respiratory syndrome (SARS), and owes its emergence from the local seafood market of Wuhan city, China. Corona virus is currently prevalent all over the world wherein it caused infection in more than 29,599,29 individuals worldwide with mortality rate nearby 6.84% in approximately 213 countries within a short span of time and the infection due to this virus is still on a higher verge. The data showed that the transmission rate of COVID-19 is higher than the previous viral infections, particularly because of changes in genetic recombination at S protein in the RBD region. Till now there is no approved treatment available against COVID-19 infection and has been observed for human to human transfer widely. The present review summarizes the etiology, transmission, epidemiology, possible approaches for the treatment of COVID-19 ...

arman rabbani

Coronavirus disease 2019 (COVID-19) has become one of the most prevalent and significant global health concerns since its origin in Wuhan, China in the December 2019. As on 05th April, this disease has affected over 131 million people and has resulted in more than 2.85 million deaths worldwide till date. The disease is transmitted from the infected patients to the people in close contact through respiratory droplets. There are a number of factors which affect the transmission of this disease. The clinical presentation of COVID-19 can range from asymptomatic infections to critical disease leading to respiratory failure, septic shock and multiple organ failure. The disease essentially affects the respiratory system but other organ systems may also be involved. Currently, the therapeutic management of the disease is based on the severity of the infection and employs various strategies like monoclonal antibodies, corticosteroids, antivirals, stem cell therapy and immunomodulators. Scien...

Saba Majeed

Aims: COVID-19 pandemic brought the medical community into action, to introduce safe and effective strategies to combat the disease. Pakistan has also experienced a significant increase in COVID-positive cases. The objective of this study is to assess the disease-related characteristics and evaluate different treatment responses in patients infected with SARS-CoV-2. Data was collected from January to September 2021. Methodology: An online survey was circulated and analyzed using SPSS and results were reported as frequency and percentages. 1000 questionnaires were distributed, of which 257 responses were received. Results: The majority of the population 90.3% survived however, a few 9.7% deaths were reported. Fever (65.7%) and cough (53.6%) were the most frequently observed symptoms. Ninety percent (n=230) of the patients required no hospital admission. The results show that 16.3% received anti-viral treatment, mainly Remdesivir. This study will help in assessing the COVID-19 patient...

Garima Dhingra

Coronavirus disease-2019 (COVID-19) is an outbreak on a scale unseen in modern human history. More than two years after the outbreak began, there are 271 million fatalities and more than 5.32 million mortalities reported globally. Vaccination has been the most successful medical intervention in the last century to minimize mortality and suffering due to infectious illnesses. Only the discovery and dissemination of an effective vaccine will probably result at the end of this pandemic. Tremendous attempts have also been made to develop secure and convenient vaccinations. Vaccination is an efficient method of preventing viral illness, stopping its spread, and developing protective immunity. Improved understanding of protective immunity and significant advances in gene editing has enabled the development of a wide range of novel vaccines by manipulating sugars, RNA, proteins, and DNA. The development of attenuated mutants, the expression of prospective antigens in live vectors, and the ...

Frontiers in Public Health

Arisha Saleem

ObjectivesThis study was conducted to evaluate COVID-19 vaccine booster dose willingness and identify predictors and factors of willingness and hesitance in the vaccinated population of Pakistan.MethodsA cross-sectional web-based survey was undertaken between January and February 2022 to highlight the public perceptions regarding the COVID-19 booster dose and evaluate the willingness to get the additional dose. Demographic information and booster dose willingness were recorded through the questionnaire. Additionally, a 5-point Likert scale was employed to explore fears and beliefs regarding COVID-19 vaccinations. Univariate and multivariate regression was performed to identify booster dose willingness and hesitance factors.ResultsOf the 787 respondents, 69.6% were females, 75.3% fell in the 18–30 years age group, 53.5% were university students or had a Bachelor's degree. Overall, a 77.8% booster dose willingness was reported. Participants showed absence or low fear levels associ...

santosh kumar rada

Since the COVID-19 emergence in December 2019, significant efforts are being made in the hunt for appropriate medical interventions. This forces scientists to produce or discover traditional curative medications, preventive vaccinations, or passive immunological techniques as quickly as possible. Therapeutic monoclonal antibodies (mAbs) have drawn a lot of interest throughout this context. COVID-19 approved Emergency Use Authorization (EUA) medications for the outpatient treatment of mild to moderate symptoms for many monoclonal antibodies (mAbs) aimed against the Receptor binding domain of the S protein of the coronavirus 2 (SARS-CoV-2). We investigated the feasibility of monoclonal antibodies for the diagnosis and treatment of COVID-19 infection in this review. Human monoclonal antibodies targeted SARS-CoV-2 viral protein domains, especially the spike protein area, and hyper-immune plasma from recovered COVID-19 patients are also included in this review. In summary, monoclonal ant...

Background: Covid-19, a zoonotic disease caused by Severe Acute Respiratory Syndrome Coronavirus - 2 (SARSCov-2) has emerged as a worldwide infection and has been declared pandemic since March, 2020, by WHO. This has brought about tremendous burden on the health care system of not only the developing or the third world countries but also that of prosperous counties of the world. The recent Covid-19 pandemic has pushed the worldwide scientific and medical community to find a solution with the help of vaccines to control SARS-CoV-2 pandemic. An effective vaccine is one which leads to synthesis of IgG antibodies against SARS-CoV-2, thus aiding the control and decline of the pandemic. Aim: This study aims to evaluate the antibody titres post 1st dose and post 2nd dose Covishield vaccination and reveals the safety and efficacy of ChAdOx1 nCoV-19(Recombinant) Covishield vaccine. Methodology: The levels of IgG antibodies were estimated in 215 subjects (both normal subjects and Covid-19 pos...

Cellular & Molecular Biology Letters

zahra payandeh

Designing and producing an effective vaccine is the best possible way to reduce the burden and spread of a disease. During the coronavirus disease 2019 (COVID-19) pandemic, many large pharmaceutical and biotechnology companies invested a great deal of time and money in trying to control and combat the disease. In this regard, due to the urgent need, many vaccines are now available earlier than scheduled. Based on their manufacturing technology, the vaccines available for COVID-19 (severe acute respiratory syndrome coronavirus 2 (SAR-CoV2)) infection can be classified into four platforms: RNA vaccines, adenovirus vector vaccines, subunit (protein-based) vaccines, and inactivated virus vaccines. Moreover, various drugs have been deemed to negatively affect the progression of the infection via various actions. However, adaptive variants of the SARS-CoV-2 genome can alter the pathogenic potential of the virus and increase the difficulty of both drug and vaccine development. In this revi...

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A detailed overview of sars-cov-2 omicron: its sub-variants, mutations and pathophysiology, clinical characteristics, immunological landscape, immune escape, and therapies.

1. Introduction

2. sub-variants of omicron variant, 3. different mutations and pathophysiology condition, 4. omicron variant-associated disease intensity, 5. clinical characteristics and symptom prevalence, 6. infection, reinfection, and transmissibility, 7. omicron entry and associated immunological features inside the host cells, 8. interaction of host ace2 and capability of binding with rbd, 9. phylogenomics and distribution of omicron and its sub-variants, 10. immune escape of emerging omicron variant and its sub-variant, 11. antiviral drugs and antibody-based therapeutics against the omicron and its sub-variants, 11.1. efficacy of antiviral drugs, 11.2. efficiency therapeutic antibodies, 12. conclusions, author contributions, institutional review board statement, informed consent statement, data availability statement, conflicts of interest.

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Chatterjee, S.; Bhattacharya, M.; Nag, S.; Dhama, K.; Chakraborty, C. A Detailed Overview of SARS-CoV-2 Omicron: Its Sub-Variants, Mutations and Pathophysiology, Clinical Characteristics, Immunological Landscape, Immune Escape, and Therapies. Viruses 2023 , 15 , 167. https://doi.org/10.3390/v15010167

Chatterjee S, Bhattacharya M, Nag S, Dhama K, Chakraborty C. A Detailed Overview of SARS-CoV-2 Omicron: Its Sub-Variants, Mutations and Pathophysiology, Clinical Characteristics, Immunological Landscape, Immune Escape, and Therapies. Viruses . 2023; 15(1):167. https://doi.org/10.3390/v15010167

Chatterjee, Srijan, Manojit Bhattacharya, Sagnik Nag, Kuldeep Dhama, and Chiranjib Chakraborty. 2023. "A Detailed Overview of SARS-CoV-2 Omicron: Its Sub-Variants, Mutations and Pathophysiology, Clinical Characteristics, Immunological Landscape, Immune Escape, and Therapies" Viruses 15, no. 1: 167. https://doi.org/10.3390/v15010167

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It spreads quickly, but just how severe is it? Omicron has scientists racing to gauge its threat.

By Emily Anthes and Lynsey Chutel

Even as scientists race to understand more about the Omicron variant and the threat it poses, one fact is abundantly clear: It spreads quickly everywhere it lands.

In South Africa, Omicron spread twice as fast as the highly infectious Delta variant. In Denmark, Omicron cases are doubling roughly every two days.

In the United States, Delta remains the dominant variant and was driving a surge in cases and hospitalizations even before Omicron emerged. Roughly 120,000 new Covid cases are being reported every day, a 40 percent increase from two weeks ago, although the figures remain below last winter’s peak.

But Omicron could soon overtake Delta, scientists said. Nationally, the share of cases caused by Omicron has increased to 2.9 percent from 0.4 percent in just a week, according to projections by the Centers for Disease Control and Prevention.

Tracking Omicron and Other Coronavirus Variants

See which countries have reported cases of the Omicron variant.

Still uncertain is how serious the consequences will be, as much remains unknown about the variant, including how likely it is to cause severe disease.

Early evidence from South Africa has raised hopes that Omicron may be milder than Delta; in one small report , researchers there noted that patients in a hospital Covid ward were less likely to require supplemental oxygen than during previous surges.

But it is still far too early, and the data sets are too small, to make broad conclusions about Omicron’s severity, especially because hospitalizations and deaths typically lag several weeks behind infections.

“I’m not counting that as good news just yet,” said Shweta Bansal, a disease ecologist at Georgetown University.

Emily Anthes is a reporter for The New York Times, where she focuses on science and health and covers topics like the coronavirus pandemic, vaccinations, virus testing and Covid in children. More about Emily Anthes

A Review on Novel Omicron Virus

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What we know about the symptoms — and the severity — of the omicron variant.

Michaeleen Doucleff

A commuter masks up for a bus ride in Liverpool, England. The omicron variant of the coronavirus has surged in the U.K. and is now dominant in the U.S. as well. There's now data indicating just how severe its symptoms might be. Paul Ellis/AFP via Getty Images hide caption

A commuter masks up for a bus ride in Liverpool, England. The omicron variant of the coronavirus has surged in the U.K. and is now dominant in the U.S. as well. There's now data indicating just how severe its symptoms might be.

When it was discovered, omicron alarmed scientists.

The variant looked wildly different from earlier versions of the coronavirus — and it quickly became clear that these mutations gave omicron an uncanny ability to sidestep our vaccines and spread very rapidly.

But it has taken longer to untangle what, if anything, sets an omicron illness apart from that of its predecessors. And most of all, does this variant cause less severe disease than the variants that have come before it?

Goats and Soda

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

With infections at all-time highs in the U.S., the clinical picture is now coming together and starting to confirm what other countries have found — a typical case of omicron not only presents slightly differently but also likely carries a lower chance of getting seriously ill.

Scientists at Case Western Reserve University have preliminary evidence that the risk of being admitted to the hospital or the intensive care unit during the omicron surge in the U.S. is about half of the risk observed during the delta surge. And this reflects what doctors across the country are now seeing firsthand with their patients.

"This is a pretty different surge," says Dr. Brendan Carr , chair of emergency medicine for the Mount Sinai Health System — where the emergency rooms are busier than ever but many of the COVID-19 patients are not sick enough to be admitted.

But as with any variant of SARS-CoV-2, your absolute risk depends on many factors, including whether you're vaccinated and boosted, your age, your overall health and your economic situation.

"In the older age group, it's still a nasty disease, even if it's less [nasty] than the delta variant," says Dr. Pamela Davis , who's a pulmonologist at Case Western Reserve University and a senior author on the new study. "You don't get off scot-free just because you happen to be infected in the time of omicron."

"While omicron does appear to be less severe compared to delta, especially in those vaccinated, it does not mean it should be categorized as 'mild,' " said the World Health Organization's director-general, Tedros Adhanom Ghebreyesus, on Thursday. "Just like previous variants, omicron is hospitalizing people and it is killing people."

Indeed, hospitalizations across the U.S. now stand at more than 126,000, and more than 1 in every 4 ICU beds is filled with a COVID-19 patient, according to the latest data from the Department of Health and Human Services.

When you get sick with omicron, what are the symptoms?

What those hospital numbers don't tell us is what a typical case looks like.

As with previous variants, the vast majority of people infected with omicron have a mix of symptoms that resolve relatively quickly and don't require hospital care.

And doctors are finding many of these cases tend to look like an ordinary upper respiratory infection. In other words, what you think of as the common cold.

"It's mostly that runny nose, sore throat and nasal congestion," says Dr. John Vanchiere , the associate director of the Center for Emerging Viral Threats at LSU Health Shreveport. "The cough is milder [than previous variants], if there's any cough at all, and fever seems to be a little less common."

This fits with early data from the U.K. showing that fever and cough are not as prevalent with omicron cases there and that the five top symptoms are runny nose, headache, fatigue, sneezing and sore throat.

With omicron, the symptoms also come on more quickly once you're infected. Several studies have found that the incubation period — the time it takes to develop symptoms after being exposed — is about three days. In contrast, delta took about four days, and the original variant took more than five.

Another difference doctors are noticing: Loss of smell and taste — considered a telltale sign of COVID-19 — is not nearly as common with omicron infections. And fewer patients have symptoms related to lower respiratory problems, such as shortness of breath, says Vanchiere, including older patients.

At the same time, it appears — anecdotally at least — that certain symptoms show up more with omicron than they did with delta. Three that have gained attention are nausea, night sweats and lower back pain.

But it's very possible that doctors and patients are simply paying more attention to these symptoms than they did with earlier variants, says Dr. Scott Roberts , an assistant professor of infectious diseases at the Yale School of Medicine.

"A lot of this is probably magnifying these symptoms under a microscope instead of clear changes," he says. "Omicron versus delta are really more similar than they are different."

And just like earlier variants, omicron can't be defined as causing only a narrow group of symptoms. As at earlier stages in the pandemic, many patients are still having some combination of fever, gastrointestinal problems, aches and pains, brain fog, weakness and, less often, trouble breathing, says Mount Sinai's Carr.

"Omicron can present in a myriad of different ways," he says.

It's also still not clear how much vaccines and prior infections are responsible for some of these early clinical impressions that omicron is causing a milder constellation of symptoms, says Dr. Daniel Griffin , who's chief of infectious diseases at ProHEALTH in New York and an instructor at Columbia University.

"It just seems that people who have been vaccinated ahead of time are getting much milder symptoms across the board," he says.

This was the case even before omicron: People who had breakthrough infections tended to have fewer symptoms — and milder ones — than those who were unvaccinated.

So if I do get omicron, what's my risk of getting very sick?

With SARS-CoV-2, the big danger is that a mild illness will turn into a life-threatening one. Although that could definitely still happen with omicron, the risk appears to be lower than it was with delta.

A study published online on Jan. 2 provides some of the first compelling evidence from the U.S. that the chance of ending up in the hospital is lower with omicron compared with the delta variant.

Scientists at Case Western Reserve University analyzed health records from more than a half-million people infected with SARS-CoV-2 across the country, including 14,000 people possibly infected with omicron from Dec. 15 to 24, after the variant became dominant.

"In this period, we still have delta circulating in the community. But you're pushing more and more and more toward the omicron variant," says Davis, who contributed to the study.

Then the researchers looked to see if there was a difference between people infected during the end of the delta wave and those infected during the early stage of the omicron wave. "The difference was huge," says data scientist Rong Xu , who led the study and is also at Case Western Reserve University. "We didn't need to do any complicated statistics to see the difference."

Xu and her colleagues found that the risk of needing to go to the ER dropped from about 15% during the delta surge to 5% during the early omicron surge (about a 70% decrease) and the risk of being hospitalized dropped from 4% to 2% (or by 50%).

If a person did end up in the hospital, the person's risk of being admitted to the ICU or being put on a ventilator also decreased substantially at the end of December compared with during the delta surge. Specifically, the risk of being admitted to the ICU fell from 0.8% to 0.4% (or by 50%) and the chance of being put on a ventilator fell from 0.4% to 0.1%.

This lower risk with omicron is also consistent with what scientists have observed in South Africa and the United Kingdom.

Xu and her team estimate that, in their study, about 60% of the people were vaccinated. So some of this lower risk could be because of vaccination, but the data altogether suggests that there is a reduced risk for hospitalization with the omicron variant compared with the delta variant.

In particular, Xu and her team observed a similar reduction in risk across all age groups, including children under age 5, who are not eligible for vaccination, and children ages 5 to 15, who may have been vaccinated but haven't been boosted.

That consistency, Xu says, suggests the reduction in severity is due, in part, to something inherent with omicron itself and not simply because of changes in vaccination status.

"So this is really something that's different between omicron and delta," Xu says. That all said, this reduction in risk doesn't mean omicron will be mild for everyone. For people who are at high risk for severe disease, such as older people or those with underlying health issues, the chance of being hospitalized is still quite significant. For example, if you're over age 65, your risk of being hospitalized with COVID-19 is still 5% with the omicron variant, which means 1 in 20 people infected in this age group will end up in the hospital. (By contrast, with the original version of the virus, the rate was 1 in 10.)

"The risk is not zero," says Xu's colleague Davis, speaking of omicron. "Many people are still going to be admitted to the ICU, and some people are still going to need to have mechanical ventilation."

That's why, she says, everyone should be vaccinated and boosted. As with previous variants, being vaccinated greatly protects you from severe disease with omicron. A study from the U.K. government, published last week, found that three doses of vaccine cuts the risk of hospitalization due to omicron by about 80% compared with a person who's not vaccinated at all.

If you do end up at the hospital, how bad is it?

Even though early data shows that omicron is milder than delta, many hospitals are packed because the sheer number of people getting infected is enormous.

And doctors are finding a key difference among their patients who are ending up in the ER or being admitted: Many are neither struggling to breathe nor dealing with perilously low oxygen levels.

Those two conditions were "a hallmark of the first disease and of delta and not nearly as prominent in omicron," says Mount Sinai's Carr.

In the past, it was basically a given that a severe case of COVID-19 would wreak havoc on the lungs, at times leading to pneumonia and uncontrolled inflammation. But this apparent change in the disease — that a severe infection in the lungs doesn't seem as common — means fewer people need supplemental oxygen or intubation.

"They're not short of breath, and really the lungs are OK," says Roberts, of Yale. These observations also line up with lab research that shows omicron does not replicate in lung tissue as well as delta.

Many of the patients who are being hospitalized often have some underlying health condition, or they're older and more vulnerable to a viral infection. "What we're seeing is something really tips these patients over the edge," says Roberts. For example, an omicron infection may lead to complications of an existing condition such as diabetes or heart failure.

But Roberts says it's still quite rare for people who are vaccinated and boosted to get seriously ill from omicron. About 80% of the patients at Yale New Haven Hospital are unvaccinated. And among those who are vaccinated, almost all have not received a booster shot.

While it's welcome news that omicron is easier on the lungs, ProHEALTH's Griffin says it's not that way for some of his patients. And among unvaccinated people, he says, an omicron infection can feel like the same unforgiving disease to him.

"If we have a patient who's younger, if we have a patient who's vaccinated, if we have a patient who recently recovered from delta, we're tending to see very mild disease with omicron," says Griffin. "But people who are fresh, with no preexisting immunity, it's hard to see that the virus is milder."

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Update on Omicron

On 26 November 2021,   WHO designated the variant B.1.1.529 a variant of concern, named Omicron, on the advice of WHO’s Technical Advisory Group on Virus Evolution  (TAG-VE).  This decision was based on the evidence presented to the TAG-VE that Omicron has several mutations that may have an impact on how it behaves, for example, on how easily it spreads or the severity of illness it causes. Here is a summary of what is currently known.  

Current knowledge about Omicron 

Researchers in South Africa and around the world are conducting studies to better understand many aspects of Omicron and will continue to share the findings of these studies as they become available.  

Transmissibility : It is not yet clear whether Omicron is more transmissible (e.g., more easily spread from person to person) compared to other variants, including Delta. The number of people testing positive has risen in areas of South Africa affected by this variant, but epidemiologic studies are underway to understand if it is because of Omicron or other factors.  

Severity of disease : It is not yet clear whether infection with Omicron causes more severe disease compared to infections with other variants, including Delta.  Preliminary data suggests that there are increasing rates of hospitalization in South Africa, but this may be due to increasing overall numbers of people becoming infected, rather than a result of specific infection with Omicron.  There is currently no information to suggest that symptoms associated with Omicron are different from those from other variants.  Initial reported infections were among university students—younger individuals who tend to have more mild disease—but understanding the level of severity of the Omicron variant will take days to several weeks.  All variants of COVID-19, including the Delta variant that is dominant worldwide, can cause severe disease or death, in particular for the most vulnerable people, and thus prevention is always key. 

Effectiveness of prior SARS-CoV-2 infection 

Preliminary evidence suggests there may be an increased risk of reinfection with Omicron (ie, people who have previously had COVID-19 could become reinfected more easily with Omicron), as compared to other variants of concern, but information is limited. More information on this will become available in the coming days and weeks. 

Effectiveness of vaccines : WHO is working with technical partners to understand the potential impact of this variant on our existing countermeasures, including vaccines. Vaccines remain critical to reducing severe disease and death, including against the dominant circulating variant, Delta. Current vaccines remain effective against severe disease and death.   

Effectiveness of current tests : The widely used PCR tests continue to detect infection, including infection with Omicron, as we have seen with other variants as well. Studies are ongoing to determine whether there is any impact on other types of tests, including rapid antigen detection tests.  

Effectiveness of current treatments :   Corticosteroids and IL6 Receptor Blockers will still be effective for managing patients with severe COVID-19. Other treatments will be assessed to see if they are still as effective given the changes to parts of the virus in the Omicron variant.  

Studies underway  

At the present time, WHO is coordinating with a large number of researchers around the world to better understand Omicron. Studies currently underway or underway shortly include assessments of transmissibility, severity of infection (including symptoms), performance of vaccines and diagnostic tests, and effectiveness of treatments.    

WHO encourages countries to contribute the collection and sharing of hospitalized patient data through the  WHO COVID-19 Clinical Data Platform  to rapidly describe clinical characteristics and patient outcomes.  

More information will emerge in the coming days and weeks. WHO’s TAG-VE will continue to monitor and evaluate the data as it becomes available and assess how mutations in Omicron alter the behaviour of the virus.  

Recommended actions for countries 

As Omicron has been designated a Variant of Concern, there are several actions WHO recommends countries to undertake, including enhancing surveillance and sequencing of cases;  sharing genome sequences on publicly available databases, such as GISAID; reporting initial cases or clusters to WHO; performing field investigations and laboratory assessments to better understand if Omicron has different transmission or disease characteristics, or impacts effectiveness of vaccines, therapeutics, diagnostics or public health and social measures.  More detail in the  announcement  from 26 November.    

Countries should continue to implement the effective public health measures to reduce COVID-19 circulation overall, using a risk analysis and science-based approach .  They should increase some public health and medical capacities to manage an increase in cases.  WHO is providing countries with support and guidance for both readiness and response.  

In addition, it is vitally important that inequities in access to COVID-19 vaccines are urgently addressed to ensure that vulnerable groups everywhere, including health workers and older persons, receive their first and second doses, alongside equitable access to treatment and diagnostics.   

Recommended actions for people 

The most effective steps individuals can take to reduce the spread of the COVID-19 virus is to keep a physical distance of at least 1 metre from others; wear a well-fitting mask; open windows to improve ventilation; avoid poorly ventilated or crowded spaces; keep hands clean; cough or sneeze into a bent elbow or tissue; and get vaccinated when it’s their turn.  

WHO will continue to provide updates as more information becomes available, including following meetings of the TAG-VE. In addition, information will be available on WHO’s digital and social media platforms. 

Reference material:   

• Classification of Omicron  (B.1.1.529): SARS-CoV-2 Variant of Concern 
• Further information  on TAG-VE 

Enhancing Readiness for Omicron (B.1.1.529): Technical Brief and Priority Actions for Member States

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Omicron SARS-CoV-2 variant: a new chapter in the COVID-19 pandemic

Salim s abdool karim.

a Centre for the AIDS Programme of Research in South Africa, Durban 4001, South Africa

b Mailman School of Public Health, Columbia University, New York, NY 10032, USA

Quarraisha Abdool Karim

Associated data.

On Nov 25, 2021, about 23 months since the first reported case of COVID-19 and after a global estimated 260 million cases and 5·2 million deaths, 1 a new SARS-CoV-2 variant of concern (VoC), omicron, 2 was reported. Omicron emerged in a COVID-19-weary world in which anger and frustration with the pandemic are rife amid widespread negative impacts on social, mental, and economic wellbeing. Although previous VoCs emerged in a world in which natural immunity from COVID-19 infections was common, this fifth VoC has emerged at a time when vaccine immunity is increasing in the world.

The emergence of the alpha, beta, and delta SARS-CoV-2 VoCs were associated with new waves of infections, sometimes across the entire world. 3 For example, the increased transmissibility of the delta VoC was associated with, among others, a higher viral load, 4 longer duration of infectiousness, 5 and high rates of reinfection, because of its ability to escape from natural immunity, 6 which resulted in the delta VoC rapidly becoming the globally dominant variant. The delta VoC continues to drive new waves of infection and remains the dominant VoC during the fourth wave in many countries. Concerns about lower vaccine efficacy because of new variants have changed our understanding of the COVID-19 endgame, disabusing the world of the notion that global vaccination is by itself adequate for controlling SARS-CoV-2 infection. Indeed, VoCs have highlighted the importance of vaccination in combination with existing public health prevention measures, such as masks, as a pathway to viral endemicity. 7

The first sequenced omicron case was reported from Botswana on Nov 11, 2021, and a few days later another sequenced case was reported from Hong Kong in a traveller from South Africa. 8 Several sequences from South Africa followed, after initial identification that the new variant was associated with an S-gene target failure on a specific PCR assay because of a 69–70del deletion, similar to that observed with the alpha variant. 9 The earliest known case of omicron in South Africa was a patient diagnosed with COVID-19 on Nov 9, 2021, although it is probable that there were unidentified cases in several countries across the world before then. In South Africa, the mean number of 280 COVID-19 cases per day in the week before the detection of omicron increased to 800 cases per day in the following week, partly attributed to increased surveillance. 10 COVID-19 cases are increasing rapidly in the Gauteng province of South Africa; the early doubling time in the fourth wave is higher than that of the previous three waves ( figure , appendix ). 10

SARS-CoV-2 cases in first, second, third, and fourth waves, Gauteng Province of South Africa

*Doubling time for the first 3 days after the wave threshold of ten cases per 100 000 population. 7-day moving average cases per 100 000 population up to Dec 1, 2021. Data are from the Department of Health, Government of South Africa. 10

The principal concerns about omicron include whether it is more infectious or severe than other VoCs and whether it can circumvent vaccine protection. Although immunological and clinical data are not yet available to provide definitive evidence, we can extrapolate from what is known about the mutations of omicron to provide preliminary indications on transmissibility, severity, and immune escape. Omicron has some deletions and more than 30 mutations, several of which (eg, 69–70del, T95I, G142D/143–145del, K417N, T478K, N501Y, N655Y, N679K, and P681H) overlap with those in the alpha, beta, gamma, or delta VoCs. 8 These deletions and mutations are known to lead to increased transmissibility, higher viral binding affinity, and higher antibody escape. 11 , 12 Some of the other omicron mutations with known effects confer increased transmissibility and affect binding affinity. 11 , 12 Importantly, the effects of most of the remaining omicron mutations are not known, resulting in a high level of uncertainty about how the full combination of deletions and mutations will affect viral behaviour and susceptibility to natural and vaccine-mediated immunity.

The impact of omicron on transmissibility is a concern. If the overlapping omicron mutations maintain their known effects, then higher transmissibility is expected, particularly because of the mutations near the furin cleavage site. Early epidemiological evidence suggests that cases are rising in South Africa and that PCR tests with S-gene target failure are also rising. Although omicron is likely to be highly transmissible, it is not yet clear whether it has greater transmissibility than delta, although preliminary indications suggest that it is spreading rapidly against a backdrop of ongoing delta-variant transmission and high levels of natural immunity to the delta variant. If this trend continues, omicron is anticipated to displace delta as the dominant variant in South Africa.

We await knowledge of how this new VoC will impact clinical presentation. At this stage, the available anecdotal data from clinicians at the front lines in South Africa suggest that patients with omicron are younger people with a clinical presentation similar to that of past variants. 13 Although no alarming clinical concerns have been raised thus far, this anecdotal information should be treated with caution given that severe COVID-19 cases typically present several weeks after the initial symptoms associated with mild disease.

Immune escape is another concern. In the absence of data on observational vaccine effectiveness and antibody-neutralisation studies on vaccinee sera, preliminary data from the national PCR testing programme could provide some clues. Data on positive PCR tests in people with previous positive tests suggest an increase in cases of reinfection in South Africa. However, the increased use of rapid antigen tests and incomplete capturing of negative results have complicated the interpretation of test positivity rates, which have risen to about four times the previous rate in the past week. Notwithstanding this limitation, the increase in cases of reinfection is in keeping with the immune-escape mutations present in omicron.

Although there are conflicting reports on whether COVID-19 vaccines have consistently retained high efficacy for each of the four VoCs preceding omicron, clinical trials have reported lower efficacy for some vaccines in transmission settings in which the beta variant is dominant. Previous variants have lowered vaccine efficacy; for example, the ChAdOx1 vaccine was 70% effective in preventing clinical infections for the D614G variant in the UK, but this efficacy decreased to 10% for the beta variant in South Africa. 14 However, the efficacy of the BNT162b2 vaccine in preventing clinical infections was retained across both the D614G and beta variants. 14 Given that omicron has a larger number of mutations than previous VoCs, the potential impact of omicron on the clinical efficacy of COVID-19 vaccines for mild infections is not clear.

Thus far, most COVID-19 vaccines have remained effective in preventing severe COVID-19, hospitalisation, and death, for all previous variants, because this efficacy might be more dependent on T-cell immune responses than antibodies. Observational studies from Qatar (n=231 826) 15 and Kaiser Permanente (n=3 436 957) 16 reported vaccine efficacy of more than 90% in preventing hospital admissions during delta-variant transmission, even up to 6 months after vaccination. Observational data from the state of New York, USA (n=8 834 604) indicated high vaccine efficacy in preventing severe disease in people older than 65 years, with varying levels of protection conferred by different vaccines—95% for BNT162b2, 97% for mRNA-1273, and 86% for Ad26.COV2.S 17 —with minimal declines in protection 6 months after vaccination.

In terms of diagnostics, the omicron variant is detectable on widely used PCR platforms in South Africa. There is no reason to believe that current COVID-19 treatment protocols and therapeutics would no longer be effective, with the possible exception of monoclonal antibodies, for which data on the omicron variant's susceptibility are not yet available. Importantly, existing public health prevention measures (mask wearing, physical distancing, avoidance of enclosed spaces, outdoor preference, and hand hygiene) that have remained effective against past variants should be just as effective against the omicron variant.

Extrapolations based on known mutations and preliminary observations, which should be interpreted with caution, indicate that omicron might spread faster and might escape antibodies more readily than previous variants, thereby increasing cases of reinfection and cases of mild breakthrough infections in people who are vaccinated. On the basis of data from previous VoCs, people who are vaccinated are likely to have a much lower risk of severe disease from omicron infection. A combination prevention approach of vaccination and public health measures is expected to remain an effective strategy.

This online publication has been corrected. The corrected version first appeared at thelancet.com on January 6, 2021

We declare no competing interests.

Supplementary Material