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Vaccine vials and syringe

FDA calls for updated COVID vaccines to target XBB variants

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The Food and Drug Administration (FDA) has instructed COVID-19 vaccine manufacturers to update vaccines to better match the circulating virus variants.

The move on Friday came just a day after the FDA's Vaccine and Related Biological Products Advisory Committee (VRBPAC) voted 21-0 in favor of switching to a monovalent vaccine containing an omicron XBB strain without the original SARS-CoV-2 strain.

Updated vaccines likely will available this fall. It will be up to the Centers for Disease Control and Prevention (CDC) to decide whether everyone should get an updated vaccine or only people in certain high-risk categories.

While COVID cases have declined, Peter Marks, M.D., Ph.D., director of the FDA’s Center for Biologics Evaluation and Research, said there could be another wave during the 2023-24 winter “during a time when the virus has further evolved, immunity of the population has waned further, and we move indoors for wintertime.”

The current vaccines include the original SARS-CoV-2 strain and omicron BA.4/5. However, nearly all circulating strains in the U.S. are omicron XBB, which also are predominant globally. The original strain and other early variants are no longer circulating. Experts also noted most people have antibodies against the original strain from vaccination, infection or both.

While the current vaccines provide some protection against XBB variants, they appear to be less effective than against previous variants, and effectiveness wanes over time, according to the FDA.

Moderna, Pfizer and Novavax presented VRBPAC with data Thursday from animal studies showing updated XBB vaccine formulations elicit stronger neutralizing antibody responses against these strains than current vaccines. A Moderna study with 101 adults also showed improved neutralizing antibody response against XBB and a similar safety profile to previous COVID vaccines.

Committee members agreed updating to a monovalent XBB vaccine would be prudent. The recommendation is in line with that of the World Health Organization’s COVID vaccine composition work group.

There was some disagreement among VRBPAC members about who should receive an updated vaccine and whether the update should be pitched to the public as an annual vaccine like flu. Last fall, health officials encouraged people to get both their flu and COVID vaccines together.

“I understand it may be convenient and most efficient to give the vaccines together, but it’s only been a few years,” said committee member Mark Sawyer, M.D., FAAP, a pediatric infectious disease specialist at Rady Children’s Hospital-San Diego. “We don’t really know what the COVID season is and may ultimately confuse people about when and where they should get vaccinated and how frequently.”

Committee member David Kim, M.D., a vaccine expert in U.S. Department of Health and Human Services, was one of the few to defend tying the updated COVID vaccines to the fall flu vaccine campaign.

“It wasn’t that long ago we were actually talking about the twindemic and discussing the need to try to get ahead of the curve … and the impact that these diseases will have together on the American public and how to leverage the infrastructure we currently have … to try to promote the uptake of COVID vaccine,” he said.

Vaccines were updated to the current bivalent formulation last fall, but only 17% of people had received one as of May 10, according to CDC data.

If the FDA authorizes the updated vaccines, the CDC will decide who should get them. The FDA said it will follow the data to determine when vaccines need to be updated in the future, but it does not expect to change them more than once a year unless there is a major change in circulating variants.  

The committee did not take a vote Thursday on which XBB strain to use but the consensus was in favor of XBB.1.5, the most commonly circulating in the U.S., which also has undergone some level of study by all three manufacturers. The three most common circulating XBB strains are relatively similar.

“We’ve always made the point we’re not chasing variants,” said Acting Committee Chair Arnold Monto, M.D., professor emeritus of epidemiology at the University of Michigan School of Public Health. “And even if other variants in this XBB lineage become more prominent, the XBB.1.5 seems to elicit appropriate antibodies.”

The FDA on Friday instructed manufacturers to use a monovalent XBB.1.5 composition.



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