Tracking the FDA advisory panel meeting on Moderna’s Covid booster

With people who received the Pfizer-BioNTech Covid-19 vaccine already in the process of getting booster shots, attention is shifting this week to what to do with people who received one of the two other vaccines in use in the U.S., the two-dose Moderna vaccine and the one-shot Johnson & Johnson product.

Members of the Food and Drug Administration’s vaccine expert panel, the Vaccines and Related Biological Products Advisory Committee (VRBPAC), are meeting today to discuss Moderna’s application for a booster shot for its product and again Friday to discuss the J&J application.

The Biden administration has made it clear that it wants to boost all Americans who have been vaccinated, suggesting they should receive an additional jab six months or later after the last dose in their original vaccine regimen. Though the World Health Organization has asked wealthy countries to hold off on using boosters to make more vaccine available to low-income countries, and some experts have argued most people don’t currently need boosters, the administration has been unswerving on this policy.


Moderna has applied for authorization for a booster for people 18 and older — the age range currently able to get the company’s mRNA vaccine. It is proposing to give less vaccine in its booster than it does in its regular jabs, 50 micrograms compared to 100 micrograms in the full dose. That difference may make Moderna boosters less reactogenic — less likely to trigger side effects — than the first two doses in its series.

Some studies have shown that the Moderna shot’s protection against mild infection wanes over time, but not yet to the same degree as has been seen with Pfizer’s vaccine. (For both vaccines, protection against severe illness appears to be holding.) And it wasn’t clear from the assessment FDA scientists wrote on the data Moderna submitted whether the agency believes a Moderna booster is needed at this time.


“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,” the FDA scientists said in a briefing document.

It is likely, though, that a Moderna booster will be needed at some point. And it is clear the administration is keen to push through with its boosters-for-all campaign. So turning down Moderna doesn’t seem like the likeliest of outcomes here.

VRBPAC meetings are never dull and today’s — which can be viewed online here starting at 8:30 a.m. ET — is unlikely to be an exception. Updates and analysis will be posted below in reverse chronological order.

— Helen Branswell

Mixing and matching isn’t on today’s agenda

7 a.m. Good morning. Grab a coffee or tea — it could be a long day.

A key question about Covid vaccines is whether they could be more effective if used in combination. There’s good reason to believe the vaccines — because they aren’t all made using the same design or platform — won’t all generate the exact same immune response. In theory, giving an mRNA vaccine after one that uses a modified virus to deliver genetic material from the SARS-CoV-2 virus — as the J&J vaccine does — might provide broader protection.

The National Institute of Allergy and Infectious Diseases has been studying this question, and a preprint containing the earliest data from that so-called mix-and-match trial was posted online on Wednesday. The data look good for the Moderna booster; it seems to work well as a booster for itself, for the Pfizer vaccine, and for the J&J shot.

But the dose studied in the mix-and-match trial was not the half dose Moderna is hoping the FDA will authorize — the study used the full, 100-microgram dose.

At any rate, mix-and-match use of the Moderna booster isn’t on the agenda for today. The NIAID data won’t be presented until tomorrow. Today’s vote — the wording of which has not yet been revealed — will be about whether people who received Moderna’s vaccine should get its booster.

— Helen Branswell

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