Booster bonanza: FDA endorses 'mix-and-match' scheme, and Moderna and J&J too

Thursday, October 21, 2021

Source: Endpoints News

The FDA late Wednesday signed off on authorizing the use of heterologous — or what FDA calls a “mix and match” of a primary vaccine series and different booster doses — for all currently available Covid-19 vaccines, in addition to separately authorizing Moderna and J&J boosters.

On the mix-and-match approach, which FDA officials insisted isn’t too confusing in a press conference, the agency offered the example of an 18-year-old who received the J&J shot at least two months ago and may now receive a single booster of the J&J, a half dose of the Moderna, or the Pfizer-BioNTech booster.

Another example would be someone who received the initial two-dose series of Pfizer or Moderna, and who is eligible to get a booster (i.e., 65 years of age and older, 18 through 64 years of age at high-risk of severe Covid-19, and 18 through 64 years of age with frequent institutional or occupational exposure to SARS-CoV-2) may receive a shot of the Moderna, Pfizer or a J&J vaccine, at least six months after completing their primary vaccination.


“Following a presentation of clinical trial data from the National Institute of Allergy and Infectious Diseases, the Vaccines and Related Biological Products Advisory Committee’s discussion of information submitted for consideration, along with the agency’s evaluation of the available data, the FDA has determined that the known and potential benefits of the use of a single heterologous booster dose outweigh the known and potential risks of their use in eligible populations,” FDA said in a statement.

At that VRBPAC meeting, experts reviewed data from a mix-and-match study where participants who received J&J’s single shot followed by a Moderna shot saw a geometric mean fold rise (the ratio of post-vaccination titer value to pre-vaccination titer value) of 76-fold, according to Kirsten Lyke of the Center for Vaccine Development and Global Health at the University of Maryland School of Medicine. That compared to a 4.2 GMFR in those who received two doses of J&J’s vaccine, and a 35 GMFR in those who got J&J’s vaccine followed by the Pfizer/BioNTech vaccine.

“What I would note is that the neutralizing antibodies did increase in response to any boost regardless of the primary vaccination series,” she said, also noting that the mRNA vaccines resulted in higher antibody titers in the first 28 days after the boost.

Other experts called for the EUA for mix-and-match boosters so that they can be tracked, as the heterologous second and third shots are occurring in the real world with or without an FDA authorization.

Ofer Levy, director of Boston Children’s Hospital’s precision vaccines program, expressed concern over recent reports that some Americans are taking matters into their own hands, receiving unauthorized boosters and mixing products.

“In the real world, all these kinds of combinations or extra boosters are already happening,” he said. “So I think it’s a matter of some urgency for FDA to help sort out what is admittedly a complicated and challenging scenario. But we can’t hide from it, and I do think we need to give guidance to the public.”

Separately, the agency also offered an EUA for a single booster half-dose of the Moderna vaccine that may be administered at least 6 months after completion of the primary series to seniors, those at high risk of severe Covid, and those who work in places where there’s a high risk of exposure to the virus.

For J&J, FDA said the booster may be administered for any adult, at least 2 months after completion of the single-dose primary regimen.

Both of those recommendations for Moderna and J&J boosters followed unanimous votes from the FDA’s vaccine adcomm.

The CDC’s Advisory Committee on Immunization Practices will vote on a recommendation today for which groups should receive boosters. It will also discuss new safety updates. But as the Pfizer booster authorization showed, the CDC director does not have to follow ACIP’s recommendations.

“We will work to accrue additional data as quickly as possible to further assess the benefits and risks of the use of booster doses in additional populations and plan to update the healthcare community and public with our determination in the coming weeks,” CBER director Peter Marks said in a statement.

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