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The CDC's vaccine advisors on Thursday recommended updated COVID-19 booster shots from Pfizer/BioNTech and Moderna that target the latest Omicron subvariants, setting aside concerns about the lack of clinical trial data with the newly formulated vaccines.

In a pair of 13-1 votes, the Advisory Committee on Immunization Practices (ACIP) recommended the bivalent vaccines from Pfizer (for individuals 12 and older) and Moderna (for individuals 18 and up) be administered a minimum of 2 months following a primary series or previous booster shot.

The updated mRNA shots contain components targeting Omicron's BA.4 and BA.5 subvariants, along with the ancestral strain of SARS-CoV-2; prior ACIP recommendations supporting the companies' monovalent mRNA vaccines as boosters have been revoked.

CDC Director Rochelle Walensky, MD, MPH, the recommendations shortly after the ACIP meeting, saying the updated boosters are formulated to better protect against the most recently circulating variants.

"This recommendation followed a comprehensive scientific evaluation and robust scientific discussion," Walensky said in a statement. "If you are eligible, there is no bad time to get your COVID-19 booster and I strongly encourage you to receive it."

CDC said it expects updated COVID-19 boosters for pediatric groups under 12 will come under review "in the coming weeks."

This marks the first time the makeup of COVID-19 vaccines have been altered since their introduction in late 2020, and many ACIP members expressed reluctance about rubber-stamping the new rollout, with concerns ranging from the lack of human data on these particular bivalent shots to the timing of administration following prior vaccine doses.

"I really feel we need the human data," said Pablo Sanchez, MD, of Ohio State University in Columbus, who made the only vote against the new boosters. "It's a new vaccine, it's a new platform, there's a lot of vaccine hesitancy already."

But Sanchez added that he's considered high risk and will almost surely take it.

"I'm not against this, it makes sense," he said. "I think the vaccine will be similar to previous ones we've seen with mRNA."

Oliver Brooks, MD, of of Watts HealthCare Corporation in Los Angeles, qualified his vote, saying he voted yes because "it's the way seasonal influenza is done."

To keep pace with seasonal influenza variant changes, updates to influenza boosters are regularly recommended without clinical trial data.

Sarah Long, MD, of St. Christopher's Hospital for Children in Philadelphia, said she "reluctantly" voted yes, noting the potential to decrease hospitalization and death.

In a presentation earlier in the day, Sara Oliver, MD, MPH, of CDC's National Center for Immunization and Respiratory Diseases, and the lead for ACIP's work group on COVID-19 vaccines, showed projections suggesting a delay in rolling out the BA.4/BA.5-targeted vaccines to November would result in 137,000 more hospitalizations and 9,700 more deaths.

Many ACIP members struggled with the recommended 2-month interval leading up to the new bivalent shot. Brooks and others said they would recommend their patients wait 6 months, unless there's a really good reason to get a booster after 2 months.

Questions about the lack of clinical trial data for both Moderna and Pfizer bivalent vaccines were woven throughout the day's discussions -- clinical data supporting the updated shots came from trials testing the companies' BA.1-targeting bivalent booster shots, which are being .

Mouse models presented by representatives from Moderna and Pfizer suggested the BA.4/BA-5-directed boosters would increase neutralization for all Omicron variants.

Few ACIP members questioned the safety profile of the updated booster vaccines, which they expected would be similar to what was observed with the BA.1-targeted shots, though the committee expressed concern the new recommendations would lead to more administration errors.

Vaccine Adverse Event Reporting System (VAERS) data presented by CDC's Tom Shimabukuro, MD, MPH, detailed reports ranging from incorrect dosing and product administered to patients of an inappropriate age, as well as the use of expired products.

"We need to provide a clear planning for when changes will occur to labeling ... that's my request of both companies," ACIP Chair Grace Lee, MD, of Stanford Medicine in California, told the committee.

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