FDA still isn't really throwing its weight behind Covid-19 vaccine boosters, Moderna's adcomm briefing docs show
Zachary Brennan
Senior Editor
As the two top vaccine experts at the FDA retired in protest over the way the Covid-19 booster shot process has transpired, the agency on Tuesday released its findings on the Moderna vaccine booster data ahead of an adcomm meeting later this week, offering the same tentative support that the Pfizer booster received.
While authorization of the Moderna booster is basically a done deal, as it was with Pfizer’s before the process began (since the post-authorization CDC advisory committee has already been scheduled), the FDA’s briefing documents make clear that the agency doesn’t find the data on booster efficacy to be particularly persuasive.
“Some real world effectiveness studies have suggested declining efficacy of Moderna COVID-19 Vaccine over time against symptomatic infection or against the Delta variant, while others have not. However, overall, data indicate that currently US-licensed or authorized COVID-19 vaccines still afford protection against severe COVID-19 disease and death in the United States. There are many potentially relevant studies, but FDA has not independently reviewed or verified the underlying data or their conclusions,” the agency said.
But overall, Moderna appears to have met what FDA has requested for a booster EUA, based on its submission of immunogenicity data from 149 participants in an ongoing Phase II study in individuals 18 years of age and older who received the primary series of the vaccine about 6-8 months prior to the booster.
And as far as safety, FDA isn’t seeing any particular issues beyond what’s been seen with the primary series, noting “solicited safety data do not show evidence of increased frequency or severity of local or systemic reactions after the booster dose (N=129) relative to dose 2 of the primary series (N=155).”
But Moderna makes the case that because of the Delta variant, the need for a booster is real.
While the efficacy of Moderna’s vaccine to prevent Covid-19 was demonstrated to be 93% after 5.3 months median follow-up, that occurred when the original strain and the Alpha variant were the major circulating SARS-COV-2 strains.
“However, decreased levels of neutralizing antibody titers 6-8 months post-primary series, particularly against VoCs [variants of concern], have been observed. Clinical trial data breakthrough infections as well as real world evidence of reduced effectiveness against the Delta variant indicate that a booster dose of mRNA-1273 for those vaccinated more than 6 months previously could be beneficial to restore antibody titers to higher than post-dose 2 levels and reduce the number of breakthrough cases particularly against VoCs,” Moderna said in its documents.
The FDA’s Vaccines and Related Biological Products Advisory Committee will convene Thursday to discuss the data. The committee will vote on whether the half-dose booster should be given at least 6 months after completion of the primary series in the same populations as Pfizer received its EUA for: individuals 65 years of age and older, adults older than 18 at high risk of severe Covid-19, and those whose jobs puts them at high risk of serious complications of Covid-19.
