Advisers to the Food and Drug Administration (FDA) on Thursday recommended a major update to coronavirus booster vaccines for the fall.
The panel of outside scientific advisers unanimously voted that the next round of shots in the U.S. should only include protection against the XBB variants that are now dominant worldwide, rather than XBB and the ancestral strain of the virus that first appeared in 2020.
The FDA isn’t bound to the outcome of the committee’s vote but usually follows its recommendation. Using a shot targeting the XBB subvariant would align the U.S. with international guidance, as well.
The current booster shots were updated last year to target both the original COVID-19 strain as well as the BA.4 and BA.5 omicron subvariants, making it a bivalent booster.
But the protection against severe disease offered by those vaccines fades over time — protection against mild illness was low to begin with — and the omicron and ancestral strains are no longer in circulation.
The FDA said studies have shown the current updated boosters provide protection against XBB.1.5, but the antibodies generated appear to be lower than what’s seen against BA.4 and BA.5.
Just 17 percent of Americans have received a bivalent booster dose since they were rolled out last year.
“We’re concerned that we may have another wave of COVID-19 during a time when the virus has further evolved, immunity of the population has waned further, and we move indoors for wintertime,” said Peter Marks, head of the FDA’s vaccine division.
The challenge for scientists is that they need to predict which strain will be dominant over the winter because the virus likely will mutate again. It’s a similar strategy to the annual flu shot, and it doesn’t always work.
Flu shots are updated each year and recommended annually for everyone older than 6 months because the strains mutate every season. So if a vaccine targets the wrong strain, it could be a miss.
But unlike the flu, panel members noted that people will still get some kind of immunity even if there’s a different variant circulating than what the vaccine targets.
Vaccine companies have been working on XBB-specific vaccines so they will be ready by the end of the summer.
Representatives from Pfizer-BioNTech, Moderna and Novavax told the panel they will have supplies ready for an XBB vaccination campaign that will align with the seasonal flu vaccination campaign.
Three subtypes of XBB are currently responsible for most of the ongoing infections in the country — XBB.1.5, XBB.1.16 and XBB.2.3 — but they haven’t caused a surge in infections or hospitalizations. COVID-19 hospitalizations and deaths are the lowest they have been since the beginning of the pandemic.
The panel did not vote on recommending a specific strain of XBB to target, but in the discussion, it seemed the companies have been using XBB 1.5, and FDA will soon make a recommendation to manufacturers.
Older adults and others who are at high risk because they are immunocompromised continue to have the highest rates of hospitalization from COVID-19, though it’s unclear whether the new vaccines will be recommended for everyone this fall.
A Centers for Disease Control and Prevention panel will meet next week to discuss the updated COVID vaccines and could discuss whether the shots will be recommended for everyone or just a select population that it will benefit the most.