"Our booster vaccine regimens work against Omicron. At this point, there is no need for a variant-specific booster," Fauci said.
He cited early results from a number of studies, including a forthcoming pre-print from the National Institutes of Health's Vaccine Research Center, showing that the Omicron variant "undoubtedly compromises" the antibodies offered by the first two shots of the Pfizer and Moderna vaccines against infection but that a third dose can substantially restore protection.
Fauci also pointed to recently published real-world data from South Africa, which suggest the first two shots of the vaccines could still offer "considerable protection" against severe disease caused by Omicron.
"The message remains clear: if you are unvaccinated get vaccinated, and particularly in the arena of Omicron, if you are fully vaccinated, get your booster shot," said Fauci.
Health authorities and drugmakers around the world have been racing to assess the highly mutated variant's impact on the protection offered by current vaccines and to determine whether booster shots would need to be changed to protect against the new strain.
In addition to reimposing mask requirements on both vaccinated and unvaccinated people, some countries have moved to accelerate their rollout of booster shots to avert a feared surge in hospitalizations. Health authorities in Europe concluded Wednesday that data support giving booster shots "as early as three months from completion of the primary vaccination."
"[T]he increased transmissibility and resulting exponential growth of cases will rapidly outweigh any benefits of a potentially reduced severity," warned a report published by the European Centre for Disease Prevention and Control.
The data cited by Dr. Fauci on Wednesday echoes similar early results released by scientists in several countries, as well as other NIH-funded research released Wednesday from researchers in Massachusetts that has yet to be peer-reviewed.
More data is expected within the coming week from Moderna and Pfizer's German partner BioNTech, which have been running experiments to assess the efficacy of their current vaccines as well as developing new versions in response to Omicron.
Moderna said they will have data on their full dose booster and "multi-valent vaccine approaches" later this week. BioNTech's executives told reporters earlier this month that they expected to have data this week on testing Omicron against antibodies from children vaccinated with two doses.
Asked on Wednesday whether vaccinated younger children would also need a booster shot to protect against Omicron, Fauci said he expected children would "have a much more robust immune response than adults" but did not rule out whether boosters may eventually be needed for kids.
"This is something that we will continue to examine, as to the possibility or necessity of providing boost for that cohort of young people," said Fauci.
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