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Fauci: Omicron ‘very different from other variants’


The newly detected Omicron COVID-19 variant may be highly infectious and less responsive to available vaccines than other variants, but it is too early to know how it compares to the Delta variant, top infectious disease official Anthony S. Fauci, MD, said Nov. 30.

Dr. Fauci, speaking at a White House COVID-19 briefing, said there’s a “very unusual constellation of changes” across the COVID-19 genome that indicates it is unlike any variant we have seen so far.

“This mutational profile is very different from other variants of interest and concern, and although some mutations are also found in Delta, this is not Delta,” Dr. Fauci said. “These mutations have been associated with increased transmissibility and immune evasion.”

Omicron is the fifth designated COVID-19 variant of concern.

Detected first in South Africa, Omicron has been found in 20 countries so far. There are no known cases yet in the United States, but it has been detected in Canada.

Omicron has more than 30 mutations to the spike protein, the part of the virus that binds to human cells, Dr. Fauci said.

Cross-protection from boosters

Though the mutations suggest there is increased transmission of this variant, he said it is too soon to know how this compares to the Delta variant. And although the vaccines may not be as effective against Omicron, Dr. Fauci said there will likely be some protection.

“Remember, as with other variants, although partial immune escape may occur, vaccines, particularly boosters, give a level of antibodies that even with variants like Delta give you a degree of cross-protection, particularly against severe disease,” he said.

“When we say that although these mutations suggest a diminution of protection and a degree of immune evasion, we still, from experience with Delta, can make a reasonable conclusion that you would not eliminate all protection against this particular variant,” Dr. Fauci said.

So far, there is no reason to believe Omicron will cause more severe illness than other variants of concern.

“Although some preliminary information from South Africa suggests no unusual symptoms associated with variant, we do not know, and it is too early to tell,” Dr. Fauci said.

He recommended that people continue to wear masks, wash hands, and avoid crowded indoor venues. Most importantly, he recommended that everyone get their vaccines and boosters.

“One thing has become clear over the last 20 months: We can’t predict the future, but we can be prepared for it,” CDC Director Rochelle P. Walensky, MD, said at the briefing. “We have far more tools to fight the variant today than we did at this time last year.”

A version of this story first appeared on

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