FDA advisory committee votes unanimously in favor of bivalent Covid shots replacing primary series

The FDA’s Vaccines and Related Biological Products Advisory Committee (VRBPAC) voted unanimously in favor of “harmonizing” Covid vaccine compositions, meaning all current vaccine recipients would receive a bivalent vaccine, regardless of whether they’ve gotten their primary series.

Paul Offit

The vote marks an effort to clear up confusion around varying formulations and dosing schedules for current primary series and booster vaccines, as well as “get closer to the strains that are circulating,” according to committee member Paul Offit, professor of pediatrics at the Children’s Hospital of Philadelphia.

“Right now, BA.4 is gone. BA.5 probably represents less than 5% of the population of what’s circulating, but it’s certainly a lot closer than Wuhan [the original strain],” he said.

As Mark Sawyer, pediatrics professor at the UC San Diego School of Medicine, summarized: “Bivalent is better. Simple is better.”

“I believe we still need to vaccinate the unvaccinated, and so anything that results in better public communication would be extremely valuable,” according to Henry Bernstein, VRBPAC member and professor of pediatrics at the Zucker School of Medicine at Hofstra/Northwell.

The decision comes amid slow uptake for updated boosters in the US, with just about 15% of those 5 years and older having rolled up their sleeves. The FDA authorized boosters for kids 6 months and older at the end of last year, though vaccine rates in children remain particularly low.

According to data from an open-label study presented by Moderna, kids 6 months to 5 years with no prior Covid infection saw a 22.9-fold increase in BA.1 neutralizing antibodies following a BA.1-specific booster dose, compared to a 12.2-fold rise in a historical control group of those who received the original vaccine.

Pfizer presented similar data suggesting “improved Omicron BA.4/5 neutralizing response” compared to the original vaccine in a subset of around 60 children evaluable between 6 months and five years in an ongoing study. In total, the study is expected to enroll about 300 kids.

In briefing documents released ahead of the meeting, the FDA proposed a simplified vaccination schedule that would require a two-dose series for some young children, older adults and those who are immunocompromised, and a one-dose series for everyone else. However, advisory committee members said they’d need more data before reaching a decision.

Archana Chatterjee

“Particularly for the young children, we would, at least I would, want to see a lot more data. The numbers are just too few for us to really make scientifically sound decisions regarding this question,” said Archana Chatterjee, dean of the Rosalind Franklin University’s Chicago Medical School.

“We need the CDC to tell us exactly who it is that’s getting hospitalized and dying from this virus. What are their ages? What specifically are their comorbidities? If they’re immune-compromised, in what manner are they immune-compromised? Did they recently get a vaccine? Were they treated with antivirals?” Offit said. “Then, and only then, can we really best make the decision about who gets vaccinated with what and when.”

FDA also said in briefing documents that it anticipates holding an assessment of Covid variants and a VRBPAC meeting “at least annually” around early June to discuss strain selection for the fall. The process, according to the agency, would be “similar in many ways to that used for seasonal influenza vaccines.”

However, multiple VRBPAC members emphasized on the call that Covid “is not influenza.”

“I think it is critically important that we pay attention to the epidemiology and what is happening with the emerging variants, how the vaccines are continuing to hold up against them,” Chatterjee said. “We’ve had much discussion today about not wanting to chase variants, and I agree with that. But on the other hand, we do have to be mindful and pay attention to make sure that vaccines continue to be effective.”

CBER Director Peter Marks said the agency “totally agree[s] with everyone.”

“This isn’t flu,” he said. “On the other hand, you know, influenza has served the model of how influenza strain selection has worked, not to a T,  but just the general model has been a very important public health advance, and so we can take the best of that model and then essentially, adjust around it.”

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