FDA’s vaccines chief sees possibility of more Covid boosters — sooner than he’d like

Peter Marks, who leads the Food and Drug Administration’s vaccines operation, is still losing sleep over Covid.

Yes, vaccines for all age groups have been authorized or approved. Yes, an updated vaccine is now available. And, yes, multiple products are in use and hundreds of millions of doses have been given in this country.

But Marks said there are other issues that weigh on him.

Chief among them is the fact that, given the rate at which SARS-CoV-2 viruses mutate, Marks thinks it’s conceivable that the booster shot people are getting now may not be the last some will need for the coming year.

“I would be lying to you if [I said] it doesn’t keep me up at night worrying that there is a certain chance that we may have to deploy another booster — at least for a portion of the population, perhaps older individuals — before next September, October,” Marks told STAT.

“I’m not saying that’s what’s going to happen, but it’s what keeps me up at night, because we see how fast this virus is evolving.”

The messenger RNA vaccines most commonly used in the United States — the products made by Moderna and the Pfizer-BioNTech partnership — can easily be tweaked to update the strains of the virus they target. The speed with which these vaccines can be adapted and produced has revolutionized pandemic response.

But the vaccines as currently designed do not offer long-term protection against infection. Severe disease, hospitalization, and death, yes. But the duration of protection against contracting Covid is short-lived — which could lead to a vaccination cadence that is impractical to try to maintain.

Marks acknowledged this worries him.

“It does,” he said, noting this problem is leading to pressure on the mRNA manufacturers to see if they can improve the durability of their vaccines. “Because there are probably things that can be done to optimize sequences and optimize constructs that would hopefully lead to better mRNA vaccines.”

But the long-term answer, Marks said, doesn’t just rest with vaccines made using mRNA.

“We need to look at other other types of vaccines. And there are those out there that might provide more durable immunity,” he said.

“I would love to see us have a very ecumenical look over all of the available vaccines and all of the vaccines in development to try to see what’s best moving forward,” Marks said. “Not to diss the current mRNA vaccines, but because we owe it to the population to see what might provide the greatest breadth, depth, and duration of immunity against Covid-19.”

Some of this work will take time, especially if federal government funding for next-generation vaccines does not come through. (And there’s currently no indication it will.)

With each successive booster that has been approved, the percentage of people who’ve gotten one has dropped. A bivalent booster, which targets both the original strain of SARS-2 and an Omicron variant, has been available since early September. To date only 19.4 million doses have been administered. The public’s Covid fatigue could disincentivize vaccine manufacturers from trying to produce better, longer-lasting vaccines, Marks suggested.

In the near term, he said he’d be happy if we could get to the point where an annual shot would suffice. “I would consider it a success at this point,” he said.

For the time being, Marks believes Covid vaccines are going to need to be updated on a regular basis, along the lines of what is done with flu vaccines.

Twice a year the World Health Organization convenes influenza experts to study the flu viruses that are circulating and choose strains for the Northern and Southern Hemisphere. The goal is to tweak the vaccine formulas so they target the strains that will be causing the most disease several months later. It is a hit-and-miss — more miss — endeavor.

The expert panel that advises the WHO on Covid vaccines has suggested eschewing that approach with SARS-2. Instead, the group, known as the Technical Advisory Group on Covid-19 Vaccine Composition, recommended updating Covid vaccines with a strain that is genetically highly distinct from the original strain, to broaden the immune system’s experience with SARS-2 viruses, choosing a version of Omicron that is no longer spreading.

When the FDA told Covid vaccine manufacturers what it wanted in updated vaccines, it did not follow the WHO advice to the letter, opting for a version of Omicron that matched the dominant version of the virus at the time the decision was made. (The virus’ rapid evolution means that strain is already being superseded by others.)

Marks said he believes trying to match the virus will be important for the next couple of years.

“What I can say is in … the short term, the next year or two, we are pursuing a flu-like chase-the-variant model,” he said.

Another near-term change Marks foresees include moving to a bivalent primary vaccine, so that anyone who is being vaccinated — whether they’re getting their first shot or their fifth — will get vaccine targeting the original strain and an Omicron strain. At present only booster shots are bivalent.

The FDA is waiting for additional data before making this move, said Marks. “Once we have those data — which we expect in the next few months — we will go to a public advisory committee meeting, probably in the first part of next year to have a discussion about moving things over to the bivalent … primary series.”

In the meantime, Marks is hoping to see an improvement in the uptake of Covid vaccine — primary series and boosters — for young children, where the acceptance rates remain very low. “It is kind of disappointing that a public health measure that is so clearly beneficial has been way under-utilized,” he said.

Get your daily dose of health and medicine every weekday with STAT’s free newsletter Morning Rounds. Sign up here.