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The next round of fall coronavirus vaccinations should target the XBB variant family, a branch of Omicron that has become dominant in the United States, vaccine experts at the Food and Drug Administration said Thursday. The FDA will make a final decision on the vaccine’s formula in the coming days.
The unanimous vote by the FDA’s independent advisory panel marks the emergence of a global consensus that the vaccine should be restarted to no longer contain the original strain from the early days of the pandemic.
The currently available version of the vaccine is bivalent, meaning it targets both the original strain and the newer Omicron variants BA.4 and BA.5. But in the four years since the coronavirus began spreading to humans, it has continued to develop new ways to circumvent existing immunities.
The newly chosen target, XBB, is a recombinant virus – a hybrid of two progeny of the BA.2 omicron variant. Several variants of XBB are circulating in the United States today, but the committee and FDA seemed to favor the use of XBB.1.5, a highly transmissible virus version of the virus on which Vaccine manufacturers have already carried out extensive tests.
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“The data clearly indicate that the old variants are no longer in circulation. XBB is. So yes, [a change] makes sense,” said Adam C. Berger, director of the Division of Clinical and Health Research Policy in the Office of Science Policy at the National Institutes of Health.
Executives from Moderna, Pfizer and Novavax, the vaccine companies that offer vaccines in the United States, presented data from animal studies and some limited human testing for various updates candidates. The potential timeline for vaccine distribution will vary depending on which strain is selected by the FDA, with companies able to provide XBB.1.5 vaccines earlier than other options.
Updating the vaccine this year was an easy decision for committee members. Still, some debated whether there was enough scientific understanding of the virus to predict that the vaccination would be updated annually, much like the flu vaccine is updated every year. Virus development is inherently unpredictable and the seasonal pattern of this virus is still evolving.
The 2023-2024 coronavirus vaccine designation “suggests that this will happen once a year, and personally I’m not sure we’re there with this virus — that it’s not necessarily seasonal,” said Henry Bernstein, professor in Pediatrics at the Zucker School of Medicine in Hofstra/Northwell in New York.
These uncertainties must be balanced against the need for a plan that allows companies to manufacture adequate doses and allows health officials to communicate clearly when people need their shots, said Peter Marks, director of the Center for Biologics Evaluation and Research at the FDA.
“I’m sure we can all agree that Covid-19 is not a flu, but from a public health perspective, where you have to make tens and millions of vaccine doses, deploy them and get them into people’s arms… reduced “It’s a similar way of campaigning,” Marks said.
A big concern could be the uptake of the vaccine. According to the Centers for Disease Control and Prevention, only one in five adults has received a bivalent booster shot.
This worries public health experts because while immunity to vaccines and infections continues to protect most people from serious illness and death, protection erodes significantly over time. Data presented at the meeting showed that protection from hospitalization decreases significantly four to six months after a bivalent booster dose. Older adults are most at risk.
“Barring some extraordinary development of a resistant virus … I think we have a chance to put vaccines into action this fall,” Marks said.
Scientists are working on a range of next-generation vaccines that could be more variant-safe, longer-lived, or stop disease transmission. In the short term, however, the most practical option is to track the virus and keep updating the vaccine as it develops – an uncertain task that several committee members have said is unsatisfactory if need be.
“We have to be prepared that this will be an ongoing process,” said Jerry Weir, director of the Division of Viral Products at the FDA’s Center for Biologics Evaluation and Research.