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Pfizer and BioNTech said Monday that they have asked the Food and Drug Administration to authorize a new booster shot targeted at the Omicron BA.4/BA.5 strain of the coronavirus that causes Covid-19, the first step in a process that could lead to more effective booster shots.

Notably, in the same press release, the companies said that a clinical study investigating the safety, tolerability, and immunogenicity of the vaccine, which also includes the original Covid strain, is expected to start this month, meaning data would not be available for the FDA to consider.

The application to authorize the vaccine without new clinical trial data is part of a bold and potentially controversial gambit by the U.S. and its advisers to try and get ahead of the fast-mutating coronavirus, SARS-CoV-2. But it’s one that could also have a big payoff.

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One of the problems for the Covid vaccines is that by the time a booster shot designed to take on a variant has gone through clinical trials – which have already been accelerated to take only a matter of months – a new variant may be on the horizon. So the FDA and its advisers have backed a plan that argues that enough is now known about the Moderna and Pfizer/BioNTech platforms to approve booster shots before clinical data are available.

Pfizer and BioNTech said that they would be able to begin shipping the new shots in September, and would do so as soon as the vaccines were authorized.

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In June, an FDA advisory panel composed of independent doctors and scientists voted 19-2 that the agency should approve an Omicron-containing booster shot, and the panelists largely supported making that shot one that contained the BA.4/BA.5 strains, not the earlier Omicron strain for which Pfizer and Moderna had already collected clinical data.

The decision is based on high confidence that the vaccine platforms, which have proven effective against earlier strains, will be effective yet again. It is also based on the hard fact that smaller studies of the vaccines are unlikely to give much information about the known side effects of the vaccines. With the existing vaccines, known issues like myocarditis, an inflammation of the heart that has mostly occurred in young men, are simply too rare to detect in even the largest clinical trials that include tens of thousands of patients. Instead, they have been detected by monitoring of vaccines once they are in broad use.

Pfizer and BioNTech said the application would also include the clinical data from their earlier Omicron vaccine. The companies asked European regulators to authorize that vaccine, which has completed a Phase 2/Phase 3 trial in July. The U.S. is deciding to go straight to a newer vaccine with less data.

But some experts could question the U.S. approach. John Moore, an immunologist at Weill Cornell Medicine, recently told NPR that he doesn’t agree. “Mouse data are not going to be predictive in any way of what you would see in humans.” (The FDA’s outside experts clearly disagreed.)

Aside from questions of clinical efficacy, the tenor of the debate could impact the bigger issue around the booster shots: whether people get them. As of June, 222 million Americans had been vaccinated but only 105 million had received a booster dose. Will the new shots make people more likely to get boosters, because they are more effective? Or will the difference in how they were developed make some reticent?

For researchers who have been developing vaccines like the mRNA shots to deal with emerging infectious diseases, the goal was always that new vaccine platforms would allow vaccines to be developed extremely quickly. In a sense, the American public is now going to be the first judge of how close scientists and public health officials have gotten to that goal.

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