The US Centers for Disease Control and Prevention's independent vaccine advisers voted 13-1 Thursday to recommend updated Covid-19 vaccine boosters from Pfizer/BioNTech and Moderna.
Both shots are bivalent vaccines that combine the companies' original vaccine with one that targets the Omicron subvariants BA.4 and BA.5.
Pfizer's updated vaccine is a 30-microgram dose authorized for people 12 and older. Moderna's updated vaccine is a 50-microgram dose authorized for 18 and older.
The Advisory Committee on Immunization Practices also voted to repeal its previous recommendations for Moderna and Pfizer's original boosters for these age groups.
CDC Director Dr. Rochelle Walensky will need to decide whether to sign off on the committee's recommendation before the shots can be administered.
An OK from the CDC would mean updated boosters could be administered within days -- both to older people who may have received a booster just a few months ago and to younger people who haven't been eligible for an additional booster during the Omicron wave.
Several members of the committee said they were uncomfortable recommending a vaccine with no data on its performance in humans to back it.
"We're been extrapolating the data that has been seen with the bivalent BA.1, and hopefully, we'll have similar data for BA.4 and BA.5.," said Dr. Pablo Sanchez, a pediatrician at Ohio State University and a member of the committee.
"So I'm just concerned about that extrapolation. And because and ultimately, I really don't want to establish a precedent of recommending a vaccine that we don't have clinical data," Sanchez says.
That prompted a quick rebuttal from government experts who work with the committee.
"I just would like to remind the committee that every year, we use influenza vaccines that are based on new strains without clinical studies being done," said Dr. Melinda Wharton, associate director for vaccine policy at the CDC's National Center for Immunization and Respiratory Diseases.
Dr. Doran Fink, deputy director of the Division of Vaccines and Related Products Applications at the US Food and Drug Administration, added, "I do appreciate the amount of discomfort that I'm hearing from committee members who are being asked to take this leap with the Covid vaccines that they haven't been asked to make previously with the Covid vaccines.
"FDA felt very comfortable with the approach of extrapolating the safety and effectiveness or rather the known and potential benefits," Fink said.
The updated boosters were authorized by the FDA on Wednesday. They do not replace shots for the primary series.
About two-thirds of the total US population is vaccinated against Covid-19 with an initial series, according to data from the CDC. But less than half of those with their initial series -- and less than a third of the total population -- has also gotten a booster.
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