Just hours after a wide-ranging discussion concluded the first day of CDC’s Advisory Committee on Immunization Practices meeting, the FDA has amended an emergency use authorization for Pfizer Inc.-Biontech SE COVID-19 vaccine, Comirnaty (tozinameran), to allow for a single booster dose for some people. The dose can be given at least six months after a completed two-dose regimen to people 65 years of age and older, those aged 18 to 64 at high risk of severe disease, and others in the 18 to 64 age group whose frequent institutional or occupational exposure to SARS-CoV-2 puts them at high risk of serious complications from COVID-19.
The latter group covers health care workers, teachers and day care staff, grocery workers and those in homeless shelters or prisons, among others.
"This pandemic is dynamic and evolving, with new data about vaccine safety and effectiveness becoming available every day," said Acting FDA Commissioner Janet Woodcock.
The authorization paves the way for the CDC’s Advisory Committee on Immunization Practices to vote Thursday, Sept. 23, on recommendations about who should receive the booster and when. ACIP’s recommendations to the CDC must align with the FDA’s authorization.
During the first day of its two-day meeting Sept. 22, some ACIP members worried about the confusion that would result if only those people who had received Pfizer’s Comirnaty as their primary vaccine were eligible for a booster, with one panelist suggesting that boosters not be used until the FDA grants an EUA for Moderna Inc.’s Spikevax vaccine as well. Moderna’s EUA request is currently under review. Johnson & Johnson said on Sept. 21 that fresh data showed COVID-19 protection dramatically increased with a booster shot of its single-dose vaccine.
Other members stressed the need for flexibility that would allow the heterologous use of the booster with other vaccines.
In acknowledgement of the rapidly changing evidence around vaccine efficacy and its duration, the FDA used less forceful language than pure certainty might have allowed. Based on the totality of the available scientific evidence, a booster dose of Comirnaty “may be effective in preventing COVID-19,” it said. Furthermore, “the known and potential benefits of a booster dose outweigh the known and potential risks in the populations that the FDA is authorizing for use,” it said.
Comirnaty gained full approval from the FDA on Aug. 23 for the prevention of COVID-19 caused by SARS-CoV-2 in people 16 years of age and older. Not long after, Pfizer applied to the regulator for approval of a single booster dose for the same group. However, members of its Vaccines and Related Biologic Products Advisory Committee put the kibosh on that idea at a meeting last week, when it voted 16-2 against such a broad approval. The committee’s primary concern was the broad age range contemplated, given that a phase III trial testing the booster only enrolled individuals between the ages of 19 and 55. (Older adults were studied in a small phase I trial.
In making its decision, the FDA said it evaluated the immune responses of about 200 participants 18 through 55 years of age who received a single booster dose approximately six months after their second dose. One month after a booster dose, “individuals demonstrated a booster response,” the agency said.
The FDA also considered data submitted by Pfizer showing that the incidence of COVID-19 among clinical trial participants who completed a two-dose vaccination series early in clinical trials experienced “a modest decrease in the efficacy of the vaccine.”
Though side effects from booster doses so far appear to be largely in line with the side effects of the primary series, it also said swollen lymph nodes in the underarm were observed more frequently following the booster dose than after the primary two-dose series. There was no discussion in the agency’s initial statement about the booster approval regarding myocarditis, an area of concern for several participants in the ACIP meeting earlier on Sept. 22.