Pfizer, BioNTech to study ‘bivalent’ booster as FDA weighs approach

Pfizer and BioNTech have begun a study testing a bivalent version of their COVID-19 vaccine that is aimed at spurring a stronger immune response against omicron and its subvariants.

The study will test a 30 microgram dose of one of two bivalent vaccine candidates in about 200 adults who received at least one booster shot 90 days or more before the study. Both vaccines share similarities to the companies’ original vaccine, sold as Comirnaty, but are designed against both the “ancestral” strain of coronavirus and either one of two omicron subvariants called BA.1 and BA.2.

The companies said these bivalent vaccine candidates are the first of several they plan to test, with this study expected to be completed in January 2023. They are also testing a single valent shot against the original omicron strain, which showed a strong immune response in initial data released in June. Moderna is also testing updated booster shots, including a bivalent shot that the biotechnology company said resulted in a stronger response against omicron than its original vaccine.

Health officials are concerned about the growing prevalence of infections by omicron subvariants BA.4 and BA.5 in the U.S. and other countries. Both strains accounted for more than 94% of infections in the U.S. last week, up from around 15% in early June, according to Centers for Disease Control and Prevention data.

In June, the Food and Drug Administration recommended vaccine makers incorporate the BA.4 or BA.5 variants in any modified booster shot.  

Single valent booster shots against omicron have worked better against the original omicron strain than the new subvariants, but researchers hope that bivalent shots could give even better protection. 

Advisers to the FDA recently recommended the next round of boosters contain some type of omicron-fighting component, but it’s still unclear exactly what those shots will look like and when they might be available.

This has posed a dilemma to health officials, who have held off recommending a second booster to adults under 50. The FDA is considering letting under-50 adults get a second booster this summer, ahead of a fall booster campaign of an updated shot. 

The U.S. secured 105 million doses from Pfizer and BioNTech in June, which at the time the companies said could include the single-valent shot tailored to omicron if cleared for use by the FDA.

But the FDA is reportedly pushing the companies to get bivalent boosters ready by October or November, National Public Radio reported, or possibly as soon as September, according to the Washington Post.

The agency could make a decision on a summer booster as early as this week, NPR reported

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