Illustration shows test tube labelled "COVID-19 Omicron variant test positive
Test tube labelled "COVID-19 Omicron variant test positive" is seen in this illustration picture taken January 15, 2022.

Advisers to the U.S. Centers for Disease Control and Prevention on Thursday voted to recommend the use of COVID-19 booster shots redesigned to target the BA.4 and BA.5 Omicron subvariants of the coronavirus for people aged 12 years and older.

The CDC's Advisory Committee for Immunization Practices (ACIP) voted 13-to-1 in favor of the updated boosters by Pfizer/BioNTech and Moderna.

The vote is one of the last steps before millions of the retooled shots roll out by the end of this weekend as part of a nationwide revaccination campaign. The agency's Director Rochelle Walensky will make the final call after the meeting. He has been supportive of a booster campaign in recent public statements.

On Wednesday, the U.S. Food and Drug Administration authorized the updated shots from Pfizer/BioNTech and Moderna that target the dominant BA.4 and BA.5 Omicron subvariants as well as the original virus. They are often called bivalent shots.

FDA officials on Wednesday said they believe the updated shots should be available to a broader population than the previous boosters as they may help younger people avoid long COVID, which can leave them suffering debilitating symptoms for months.

The FDA authorized the Pfizer/BioNTech shots for people ages 12 and older and the Moderna booster for those 18 and over, if they have received a primary vaccine series or a booster at least two months prior. The previously authorized monovalent vaccine will no longer be available as a booster shot in those age groups.

Pfizer said on Thursday it hopes to ask the FDA for authorization in 5- to 11-year-olds in early October.

CDC and FDA officials have said they believe the shots will boost immunity against the virus ahead of the winter season, when infections tend to rise as people spend more time indoors where the virus is more easily transmitted.

Currently, a second booster is restricted largely to people over age 50 and those who are immunocompromised or at high risk.

During the meeting, CDC officials suggested people who have had COVID should wait at least until they have completed their isolation to receive a booster and may consider waiting 3 months.

Vaccine makers have yet to complete human trials for the newly authorized boosters, and some ACIP members raised reservations over the lack of data. Most of the available data on the redesigned boosters comes from lab and animal studies.

"I understand we need better vaccines because obviously we're still having a lot of COVID despite vaccination," said committee member Dr. Pablo Sanchez, a Professor of Pediatrics

at Ohio State University, who voted against the recommendation. "But I'm struggling with making a recommendation for a bivalent vaccine that has not been studied in humans."

The FDA had in June said it would not require studies testing the shots in humans for authorization, similar to how annual changes to flu vaccines are cleared.