Food and Drug Administration (FDA) advisers on Thursday recommended updating Covid vaccines to target a circulating strain of the virus, while pushing for newer vaccines that provide longer-lasting protection.
The FDA’s Advisory Committee on Vaccines and Related Biologicals voted unanimously to modify the injections to target an XBB strain, as well as remove the original strain of coronavirus from the formulation.
However, the committee did not make a formal recommendation on which specific XBB lineage the updated boosters should target, nor did it make a recommendation on who should receive the vaccines and when. The latter will likely be left to the Centers for Disease Control and Prevention, which has its own advisory committee meeting next week.
The recommendation will now be given to the FDA, which is expected to make a final decision on which strain of Covid to target soon. Drugmakers need ample time to produce and distribute the new injections, which are expected to be used starting in September as part of a fall booster campaign.
Pfizer said it could distribute reformulated doses in late July, depending on the strain selected. Moderna said it hopes to start shipping updated doses, pending FDA approval, «by the end of the summer.» Novavax said it may have updated dosages available in the fall.
It is not yet clear if fall is the best time to offer reinforcements. The spread of Covid has often been erratic over the past 3 years, without the clear seasonality seen with viruses like the flu.
“This season will be very telling whether or not Covid settles into a seasonal pattern,” said Ruth Link-Gelles, a CDC senior epidemiologist.
During Thursday’s discussion, many committee members seemed in favor of updating the boosters to target XBB.1.5, a descendant of XBB that began circulating widely last fall and winter and is the predominant strain in the United States. XBB itself is a descendant of two sub-variants of omicron.
XBB.1.5 «seems to be at the front of the line,» said Dr. Peter Marks, the FDA’s chief vaccine regulator.
XBB.1.5 accounts for about 40% of all new Covid cases as of Saturday, according to the Centers for Disease Control and Prevention. It is followed by XBB.1.16 (also called «Arcturus» on social media) and XBB.1.9.1. While the CDC no longer tracks levels of Covid spread in communities, the agency’s data shows that hospitalizations have been reduced. downward trend since March.
Updating the vaccine with an XBB strain «makes more sense,» said committee member Dr. Mark Sawyer, an infectious disease specialist at the University of California San Diego School of Medicine. “I think the data is pretty clear.”
The XBB strains are not genetically too different from the next ones, which means that an XBB.1.5 vaccine should work well against the newer strains, the committee members said.
According to new data from CDC scientists, current boosters provide protection against XBB.1.5, although not as much protection as BA.4 and BA.5, two strains no longer circulating in the US ( The current boosters were formulated to attack these strains, as well as the original coronavirus strain.)
On Thursday, drugmakers presented data from animal studies suggesting that a vaccine containing XBB would provide more protection against current circulating strains than current boosters.
Choosing to target an XBB strain is in line with a World Health Organization recommendation in May, as well as the European Medicines Agency, which recommended using XBB-containing vaccines in June.
This will be the second time that Covid vaccines have been updated in the US, after the FDA cleared the BA.4/BA.5 boosters last year.
In addition to adding an XBB strain, the committee supported removing the original coronavirus strain from the vaccine, with several members saying they saw no advantage in including it. That strain has been included in vaccines since they were first licensed in December 2020, but has long been out of circulation globally.
Jerry Weir, director of the Division of Viral Products in the FDA’s Office of Vaccine Research and Review, said that an XBB-only vaccine could improve vaccine efficacy because the immune system will not be hampered by its response to the vaccine. original strain of the coronavirus, a phenomenon known as immunological imprinting.
“I think removing the ancestral strain will do something to optimize the response,” he said.
While the committee supported updating the boosters, some members stressed the need to invest in finding more effective and long-lasting vaccines. Existing vaccines are very effective, particularly against serious diseases, but their effectiveness against infection usually wanes after a few months.
“People are tired of the pandemic, people feel like we have vaccines, we’re done,” said Dr. Ofer Levy, a committee member and director of the Precision Vaccines Program at Boston Children’s Hospital, “but I think our discussion it reflects the challenge ahead and the need for further innovation.”
Uptake of booster vaccinations has been low to date. Only 17% of the US population has received an upgraded booster, according to the cdc.