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Fact Sheet: COVID-19 omicron variant

The omicron variant of COVID-19 was first reported in November and has spread across the world, including in the U.S. Here’s what we know about the variant.

The World Health Organization (WHO) on Nov. 26 designated a new COVID-19 variant, named omicron, a variant of concern. Since then, governments, health organizations and researchers across the world have worked to find out more about the variant and its impact on the pandemic.

The VERIFY team used information from multiple sources to explain what is known - and not known - about the omicron variant.



  • Dominant variant in the United States: The first omicron case in the U.S. was detected on Dec. 1. By the week ending Dec. 25, it was the most dominant strain of new COVID-19 cases in the U.S. 
  • More transmissible, appears to be less severe: The head of the WHO says there is consistent evidence omicron spreads faster than the delta variant. He also said omicron likely causes less severe disease, but warned it can still be deadly and overwhelm hospital systems. 
  • Booster shots likely enhance protection: Researchers are studying how effective vaccines are against omicron. While there’s still more to learn, studies suggest a booster shot provides greater protection.


When and where was omicron first discovered?

The WHO said the variant was first reported to it on Nov. 24 by researchers in South Africa. Two days later, the WHO dubbed the variant “omicron” and classified it as a variant of concern.

Although South Africa first reported the variant to the WHO on Nov. 24, the variant has been traced to samples taken prior to that day. 

The WHO says the first known confirmed infection was taken from a sample collected on Nov. 9 in South Africa. The Botswana government said samples from four foreign nationals showed they tested positive for omicron as early as Nov. 11. The Centers for Disease Control and Prevention (CDC) said the earliest report of symptoms from a person who tested positive for omicron was on Nov. 15. A health agency in the Netherlands says it found the omicron variant in test samples taken on Nov. 19 and 23

How far has omicron spread?

According to CDC data, omicron represented an estimated 99.5% of new COVID-19 cases in the U.S. from Jan. 9-15.

The first omicron case in the U.S. was reported in California on Dec. 1

Omicron cases have been reported in more than 100 countries. In a statement on Jan. 11, Dr. Hans Henri P Kluge, WHO Regional Director for Europe, said 50 of the 53 countries in Europe and central Asia have reported cases of Omicron. He added that it was quickly becoming the dominant variant in western Europe and was spreading in the Balkans. 

How did omicron get its name?

The WHO uses letters of the Greek alphabet to name COVID-19 variants. The decision was made, in part, to avoid placing stigmas in areas where variants are first reported.

“People often resort to calling variants by the places where they are detected, which is stigmatizing and discriminatory,” the WHO said in a May 2021 news release. “To avoid this and to simplify public communications, WHO encourages national authorities, media outlets and others to adopt these new labels.”

The variant named prior to omicron was mu, meaning the WHO skipped nu and xi. The WHO said it skipped nu to avoid confusion with the word “new,” and skipped xi because it is a common surname. Under the WHO’s best practices, disease names may not include geographic locations, people’s names, species/class of animal or food, terms that incite undue fear, and cultural, population, industry or occupational references. 

For those reasons, the WHO skipped nu and xi and named the latest variant omicron.

Why was omicron designated a variant of concern?

A COVID-19 variant is labeled a variant of concern when it could significantly impact global public health in one of the following ways, according to the WHO:

  • Increase in transmissibility or detrimental change in COVID-19 epidemiology;
  • Increase in virulence or change in clinical disease presentation;
  • Decrease in effectiveness of public health and social measures or available diagnostics, vaccines, therapeutics. 

There are currently five variants of concern: alpha, beta, gamma, delta and omicron.

The WHO classified omicron as a variant of concern because its many mutations suggested it was more transmissible and could put people at a higher risk for reinfection. Because of those factors, the WHO said the overall global risk related to omicron is “very high.”

Is omicron more transmissible?

“There is now consistent evidence that omicron is spreading significantly faster than the delta variant,” Dr. Tedros Adhanom Ghebreyesus, the director-general of the WHO, said in a speech on Dec. 20.

As of Jan. 19, the seven-day average of new COVID-19 cases was 744,615, according to CDC data. That is compared to a seven-day average of 138,484 new COVID-19 cases as of Dec. 19, 2021. 

The CDC says anyone infected with the omicron variant can spread the virus to others, regardless of their vaccination status. 

Does omicron cause more severe illness?

During a press briefing on Jan. 18, WHO director-general Tedros said omicron "may be less severe" but "the narrative that it is a mild disease is misleading," as it is still causing hospitalizations and deaths. Less severe cases are also inundating health care facilities, he added.

During an earlier press briefing on Jan. 6 , Dr. Maria Van Kerkhove, the WHO’s COVID-19 technical lead, also said that while omicron is generally causing less severe disease, there are still more people vulnerable to the worst of its effects.

“Omicron is not the common cold, it can still cause severe disease, particularly among people who are not vaccinated but of course people of older age, people with underlying conditions and we're just starting to do analyses on the data coming in from countries and seeing data from countries that exhibit this,” she said.

On Jan. 5, Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases (NIAID), cited multiple studies that he said showed omicron likely causes less severe disease than delta. One of those studies, which has not been peer-reviewed, was done in Canada. Compared to delta cases, the study found the risk of hospitalization or death among omicron cases was 65% lower, and the risk of intensive care unit admission or death was 83% lower.

In the United Kingdom, data suggests the most common symptoms for people with suspected or confirmed omicron infections were runny nose, headache, fatigue, sneezing and sore throat.

Have any omicron-related deaths been confirmed?

The first omicron-related death reported in the U.S. was on Dec. 20 by Harris County Public Health in Texas. The person who died was a man between the ages of 50 and 60. He was unvaccinated and had previously been infected with COVID-19.

The United Kingdom Health Security Agency said as of Dec. 29, 75 people infected with the omicron variant had died in England. As of that date, 212,019 omicron cases had been confirmed in England.

How effective are vaccines against omicron?

Studies are underway to determine how effective the COVID-19 vaccines are at protecting against omicron. There are some preliminary results, but more research needs to be completed to determine conclusive answers.

During a White House press briefing on Dec. 15, Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases said early studies show the omicron variant “undoubtedly compromises the effects of a two-dose mRNA vaccine-induced antibodies and reduces the overall protection.” But, he said, the vaccines still provide “considerable protection” against severe COVID-19 and that booster shots work against omicron.

Pfizer said initial lab tests suggested that a booster shot of its vaccine offered more protection against omicron than just two doses of the vaccine.

“Although two doses of the vaccine may still offer protection against severe disease caused by the omicron strain, it’s clear from these preliminary data that protection is improved with a third dose of our vaccine,” Pfizer CEO Albert Bourla said in a news release on Dec. 8.

The United Kingdom Health Security Agency published an analysis in December about the effectiveness of the vaccines produced by Pfizer and AstraZeneca, the latter of which is not authorized in the U.S., against omicron.

“Preliminary data showed effectiveness against the new variant appears to increase considerably in the early period after a booster dose, providing around 70% to 75% protection against symptomatic infection,” the UK Health Security Agency said.

Moderna said in its preliminary studies, a booster of its COVID-19 vaccine increased antibodies 37-fold.

Fauci said a study by the National Institute of Allergy and Infectious Diseases, which has yet to be peer-reviewed, showed a third dose of the Moderna COVID-19 vaccine improved antibody response to the omicron variant. 

Do you have to be tested for COVID-19 before flying domestically in the U.S.? 

You do not have to be tested for COVID-19 before flying domestically in the U.S.

With the increasing spread of omicron, WHO director-general Tedros on Dec. 20 urged caution.

“An event canceled is better than a life canceled,” he said. “It’s better to cancel now and celebrate later than to celebrate now and grieve later.”

The CDC says you should not travel if:

  • You have been exposed to COVID-19, unless you are fully vaccinated or recovered from COVID-19 in the past 90 days.
  • You are sick.
  • You tested positive for COVID-19 and haven’t ended isolation (even if you are fully vaccinated).
  • You are waiting for results of a COVID-19 test. If your test comes back positive while you are at your destination, you will need to isolate and postpone your return until it’s safe for you to end isolation. Your travel companions may need to self-quarantine.

Do you have a question about the omicron variant? Email our team at questions@verifythis.com or text us at 202-410-8808.

More from VERIFY: Omicron variant: Don’t wait to get a booster shot, doctors say

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