An FDA advisory committee on Thursday voted 19-0 to authorise a booster of Moderna's COVID-19 vaccine mRNA-1273 for people aged 65 and older, and to anyone 18 and older considered to be at high risk of severe disease or frequently exposed to the virus because of their living or working situations. The recommendation is in line with what the FDA and US Centers for Disease Control and Prevention (CDC) authorised for Pfizer and BioNTech's Comirnaty boosters last month.
In briefing documents released earlier this week ahead of the panel meeting, FDA scientists adopted a fairly neutral tone about Moderna's shot, noting – as they had with Comirnaty – that vaccines currently authorised for use in the US still afford protection against severe COVID-19 disease and death.
Following the unanimous vote Thursday, committee member Patrick Moore suggested the data that Moderna had submitted with its booster request "was not well explained," but he voted yes more on a "gut feeling." Moore added "the data itself is not strong, but it is certainly going in a direction that is supportive of this vote."
A final FDA decision on Moderna boosters could come within days, with a CDC vaccine advisory committee then expected to vote on the FDA's proposal next week. If it recommends approval and the CDC endorses it, booster shots could begin immediately for eligible Americans.
If given the green light, Moderna's booster will be administered at least six months after the current two-dose primary series of 100µg. It will also be given at a dose of 50µg, as opposed to the full dose for Pfizer/BioNTech's Comirnaty booster. Moderna has said real-world data for its vaccine show waning protection among double-vaccinated people amid the current Delta variant surge. However, even at a half dose, the mRNA-1273 booster was found to return antibody protection to initial levels after the first two shots. Jacqueline Miller, who presented Moderna's data on Thursday, said the company chose the half dose because it was just as effective, but would "increase the worldwide vaccine supply of mRNA."
Meanwhile, Paul Offit, another member of the FDA advisory panel, stressed that most people who have received the first two doses of Moderna's vaccine remain well protected, and said he hopes the recommendation does not send the "wrong message" to the general public. "If we're trying to prevent what is inevitable, which is a decline in neutralising antibodies and an erosion in protection against mild or asymptomatic infection, that is a high bar to which we hold no other vaccine," he added.
The FDA panel convenes again on Friday to discuss whether to recommend an extra dose of Johnson & Johnson's single-shot Ad26.COV2.S vaccine.
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