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CDC encourages COVID vaccination, boosters to protect against omicron variant

November 30, 2021

Update: The CDC announced the first case of omicron in the U.S. on Dec. 1. The person was a traveler who returned to California from South Africa. The person was fully vaccinated, had mild symptoms and is improving.

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Federal health officials are ramping up surveillance for the SARS-Cov-2 omicron variant and encouraging people to get vaccinated and boosted.

“We don’t know everything we need to know yet about the omicron variant, but we know that vaccination is a safe and effective way to protect yourself from severe illness and complications from all known SARS-CoV-2 variants to date.” Centers for Disease Control and Prevention (CDC) Director Rochelle P. Walensky, M.D., M.P.H., said in a news conference Tuesday.

Officials expect it to take several weeks to know more about omicron’s transmissibility, response to vaccines and whether it has potential to cause severe disease. Below is a primer on what experts know so far.

Detection of omicron

The omicron was first reported in mid-November in Botswana and South Africa and is the fifth to be named by the World Health Organization as a variant of concern. At least 226 cases had been reported in 20 countries as of Tuesday morning, but it has not yet been detected in the U.S., according to Anthony Fauci, M.D., chief medical adviser for President Joe Biden.

The CDC is performing genomic sequencing on about 80,000 samples per week, Dr. Walensky said. About one in every seven positive polymerase chain reaction (PCR) tests is sequenced. 

Last week, the State Department announced travel restrictions from several African countries. Officials also are expanding testing in four international airports in New York, Newark, San Francisco and Atlanta.

“We have the tools and surveillance in place to identify the omicron variant,” Dr. Walensky said. “We also have the tools to prevent omicron from increasing the strain on our society and our health care system.”


The omicron variant has about 50 mutations including more than 30 in the spike protein, according to Dr. Fauci. Some of the molecular characteristics suggest the virus can spread more easily than the original pandemic virus, but experts don’t know yet whether it is more transmissible than the delta variant that has been circulating widely in the U.S.

Disease severity

Dr. Fauci said Tuesday no unusual symptoms have been reported in cases in South Africa, but it is too soon to know whether the omicron variant causes more severe disease than other variants.


The PCR and antigen tests widely used in the U.S. “show low likelihood of being impacted and continue to work,” the Food and Drug Administration said Tuesday.


Experts do not yet know how effective current vaccines will be against omicron, but they expect them to provide some level of protection. People ages 5 years and older are eligible to be vaccinated.

The CDC says all adults should get boosted six months after their second dose of an mRNA vaccine or two months after the single-dose Johnson & Johnson vaccine. The language is a change from earlier in the month when it said those 50 years and older should get boosted and those under 50 may get boosted. People ages 12 years and older who are moderately or severely immunocompromised should receive an additional primary dose of the same mRNA vaccine 28 days or more after their primary series.

“There’s every reason to believe as we talk about boosters, when you get a level (of antibodies) high enough you are going to get at least some degree of cross-protection particularly against severe disease,” Dr. Fauci said.

Pfizer may soon request permission to offer boosters to 16- and 17-year-olds, according to a Washington Post report.

U.S. officials are working with vaccine manufacturers Pfizer, Moderna and Johnson & Johnson to prepare for the possibility vaccines need to be modified in response to the omicron variant. They estimate the process of development, federal approval and manufacturing would take several months.

Other means of protection

Health officials are encouraging everyone to continue the prevention measures they have been recommending throughout the pandemic including frequent hand washing, wearing masks, avoiding crowds, physical distancing and testing and quarantining/isolating as appropriate.

“These methods work to prevent the spread of COVID-19 no matter the genetic sequence, “Dr. Walensky said.



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