US government advisers have recommended changing the design of Covid-19 vaccines to target the Omicron variant for a booster campaign aimed at blunting an expected surge of infections in the autumn.
Scientists on a Food and Drug Administration advisory committee on Tuesday voted 19 to two in favour of incorporating genetic material from the fast-spreading Omicron variant into a new generation of booster jabs.
The recommendation, if approved by US authorities, would pave the way for Moderna and Pfizer to switch manufacturing operations over to making vaccines that experts believe will provide better protection against the most widely circulating Covid variants.
It would also mark the first change to the composition of the most commonly used Covid-19 vaccines since they were introduced in December 2020.
Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research, said authorities are trying to get ahead of the virus by matching vaccines more closely to the most widespread strains to provide broader and more durable protection.
“You know, for something that’s only nanometres in size, it’s [the virus] pretty darn crafty,” he said.
Global regulators are debating how best to respond to a wave of infections caused by Omicron subvariants BA.4 and BA.5 amid concerns that levels of immunity provided by vaccinations and boosters are waning.
Advisers to the World Health Organization have said that Omicron-based jabs may be beneficial as boosters, rather than as a replacement for primary vaccinations, because they would broaden protection against different variants.
Kanta Subbarao, a virologist who chairs a WHO committee, told the FDA panel that it was important that any changes did not cause the world to lose confidence in the vaccines, which continue to provide protection against severe disease and death.
The FDA committee did not vote on which specific Omicron strain the boosters should target — a critical decision that the agency is expected to make early next month.
Moderna has urged regulators to authorise its two-strain bivalent booster, which incorporates the genetic code of the Omicron variant and the original strain of the virus.
The company said it would have a “couple of hundred million” doses ready by September and has begun manufacturing at its own risk.
But several committee members urged the FDA to recommend that manufacturers target the BA.4 and BA.5 subvariants, a move that would likely delay its rollout of boosters until October.
Justin Lessler, professor of epidemiology at the University of North Carolina, presented modelling on the future course of the pandemic to the FDA committee based on the effects of waning immunity and the emergence of new variants.
Under an optimistic scenario, there would be 95,000 deaths from Covid in the 12 months to the end of March 2023. Under a pessimistic scenario, there would be 211,000 deaths, he said.
Lessler told the committee the autumn could prove to be a difficult period for the US because of resurgences in Covid variants and faster waning of immunity from vaccines. “The incidence is tracking with more pessimistic scenarios,” he added.