Will there be a new Covid vaccine in the fall?

While Covid cases remain low in the US, vaccine experts are already looking ahead to winter, aiming to avoid a seasonal surge.

A Food and Drug Administration advisory panel unanimously recommended Wednesday that fall Covid vaccines be updated to target the highly contagious JN.1 variant or one of its descendants.

JN.1 emerged in the US in late August and in January became the dominant strain in circulation.

Several branches of JN.1 soon followed, including the so-called FLiRT variants, KP.1.1 and KP.2. In mid-May, KP.2 surpassed JN.1 as the dominant strain in the U.S. and is now responsible for more than 1 in 4 new cases, according to the Centers for Disease Control and Prevention.

Natalie Thornburg, a research microbiologist at the CDC, said at Wednesday’s meeting that the coronavirus appears to be adopting a consistent pattern: A dominant “parent” strain takes hold in early winter, and in the spring a handful of offspring emerge. That’s also what happened with the XBB strain last year, she said, which dominated in the winter but gave rise to offshoots in the spring.

The panel’s recommendation did not specify whether to include the JN.1 “parent” strain or one of its descendants, but most panel members expressed a preference for JN.1.

“The tree trunk is probably our best bet for now,” said panel member Dr. Bruce Gellin, head of global public health strategy at the Rockefeller Foundation, in a discussion after the vote.

Dr. Peter Marks, the FDA’s chief vaccine regulator, urged the committee to consider one of the newer strains, such as KP.2.

“We are paying an incredibly high premium for mRNA vaccines so we can have the freshest vaccines,” Marks said, a reference to the speed at which new mRNA-based vaccines can be developed and produced.

“Will we regret not being a little closer?” he added.

The FDA is expected to make a final decision soon on which strain it will recommend to drugmakers. This will begin production of the updated vaccines, which will be distributed as part of a vaccination campaign in the fall.

Pfizer said Wednesday it will have updated Covid vaccines available “immediately upon approval” from the FDA; Moderna has said it may have shots available for distribution as early as mid-August.

Novavax said it is on track to have an updated vaccine targeting JN.1 available in August. However, should the FDA select a different strain, the company said it will not have an updated vaccine for that specific strain available for the fall vaccination campaign. Novavax uses a protein-based vaccine, which takes longer to manufacture than the mRNA-based vaccines made by Pfizer and Moderna.

All three drugmakers presented data on Wednesday showing that a JN.1 vaccine should generate higher levels of antibodies against circulating strains of the virus compared to the current vaccine, which is directed against XBB.1.5, a subvariant that no longer exists. is in circulation. Once the updated vaccine is available, the older vaccine will be discontinued.

Covid hospitalizations remain at the lowest levels since the start of the pandemic in 2020, although there are some indications that cases may be starting to rise.

CDC data shows that as of May 25, the weekly test positivity rate was 4.2%, up from 3.4% the previous week. By comparison, in early 2022, when the omicron variant began to spread rapidly, the weekly test positivity rate was around 30%.

Thornburg said virtually all Americans have developed some form of immunity to Covid, whether through infection, vaccination or a combination of both.

“We are just below 100% seroprevalence,” she said, referring to the number of people in a population who have been exposed to a virus.

Later this month, a CDC advisory group will make recommendations about who should get the vaccine in the fall.