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An independent panel of Food and Drug Administration advisers is meeting on Tuesday as members consider options for updating coronavirus vaccines for a recall campaign aimed at warding off fall or winter surges.

Experts will vote at the end of the day-long meeting on whether vaccines should be reformulated to target Omicron or its subvariants, even though the virus could evolve again by fall. You can watch the meeting live on YouTube here.

Dr. Peter Marks, who oversees the FDA’s Office of Vaccines, said at the start of Tuesday’s meeting that a good match between a vaccine and a variant could lead to greater vaccine efficacy and durability. He said the Omicron sub-variants known as BA.4 and BA.5 were “on the verge of becoming the dominant variant”, a hint of what regulators might be looking for when choosing a new composition for coronavirus injections. Shortly after his remarks, the Centers for Disease Control and Prevention released new estimates showing the two subvariants now account for more than half of new cases nationwide.

Dr Marks posted a timetable suggesting that regulators would decide on the composition of a new vaccine in early July and that a fall booster campaign with a newly designed vaccine could start in October. Makers of so-called mRNA vaccines, made by Moderna and Pfizer-BioNTech, need about three months to start producing doses with a new composition.

The advisory group will also be asked whether vaccines that combine the original formulation with an Omicron target would be preferable to vaccines that only target Omicron. The data supporting the option that combines so-called “prototype” or existing vaccines with Omicron has so far received mixed reviews, with regulators suggesting in briefing papers that such a design is “already somewhere.” little outdated”.

Regulators also plan to ask advisers whether healthcare providers should continue to use the original formulation of the vaccine this fall on people who have not yet been fully vaccinated if the composition of the booster changes.

FDA committee members may be divided on who should receive new vaccines. Some might say that a fall booster will be badly needed, while others might argue that because current vaccine protection against severe forms of Covid-19 has held, the next round of vaccines should be limited to people at high risk, at least at first.

CDC epidemiologist Heather Scobie presented data at Tuesday’s meeting showing that Americans 70 and older have been hospitalized in recent months at significantly higher rates than other age groups. Despite low uptake, it showed data indicating that second boosters reduced the risk of death in older adults. While determining the next stage of the vaccination campaign, she said, public health officials should “push second boosters in the elderly to protect against serious illness.”

The possibility of a more advanced vaccine has been teased for months by federal health officials, who have warned that as the virus rapidly evolves, vaccine-induced protection against infection has waned, allowing some Americans to be reinfected even within months.

In the backgrounder, FDA officials said the risk of another major outbreak would increase later this year “due to the combination of waning immunity, new variant evolution, and increased inner activity”. Justin T. Lessler, an epidemiologist at the University of North Carolina at Chapel Hill, presented a series of projections on the trajectory of the pandemic in the coming months in the United States.

In the most optimistic scenario, his team predicted 95,000 deaths in the 12-month period ending in March 2023. In the most pessimistic scenario, the nation would suffer more than 200,000 deaths. He said his team’s worst-case scenarios, which tried to account for declining immunity and the emergence of new variants, were more accurate so far.

Still, he warned that the unpredictable nature of the pandemic made it difficult to make assumptions about new variants and the havoc they could wreak.

“That’s the problem, because we’re being asked, more or less, to have a crystal ball today,” said Dr. Arnold S. Monto, a University of Michigan epidemiologist and chair of the committee of the FDA.

Moderna and Pfizer, the makers of the two most widely used vaccines in the United States, have both studied Omicron-specific vaccines, expecting them to be seriously considered as the fall booster option. But the search was complicated by the sub-variants, for which neither company has yet developed plans.

Pfizer showed preliminary panel data from a mouse trial suggesting that a vaccine combining the prototype with BA.4 and BA.5 worked better against all Omicron subvariants than the existing vaccine. A company official said researchers don’t yet have a side-by-side comparison with a version targeting Omicron itself.

Pfizer may be able to meet an October deadline with a vaccine that targets the latest subvariants, according to people familiar with the company’s operations. But Moderna said such an option likely won’t be ready until late this year or early next year.