Omicron boosters are in the works, but will they be needed?

Moncef Slaoui, the former head of the Trump administration's Operation Warp Speed, says he's "cautiously optimistic" about how well existing vaccines will hold up against omicron, the latest coronavirus variant of concern.

Omicron has more mutations than previous variants, with around 30 mutations on just its spike protein.

That's worrying for virologists, who note that the spike protein is what vaccines use to "teach" our bodies to recognize the coronavirus.

But Slaoui, who spent decades developing vaccines in the pharmaceutical industry before leading Operation Warp Speed's scientific work, says even if antibodies prompted by vaccines are less effective against omicron, other parts of the immune response could still help.

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"It's a race between how fast the virus replicates and how fast the immune response gears up to eliminate it," he says.

The cellular response to omicron could be the key

Vaccines prime the immune system and give it memory. "Then our capacity to mount a rapid immune response, I believe, will always be there to clear the virus. ... Maybe we get ill for a day or two. Maybe we have [a] cough. Maybe we have a bit of fever. But we're not going to have severe disease."

Slaoui says the vaccines do more than just prompt the creation of antibodies. They also build a cellular response, which includes B cells and T cells. He says T cells in particular should be able to recognize and react to parts of the omicron variant, called epitopes, even if the spike protein is different.

"There's still a lot of potential T cell epitopes spread all over the sequence of the protein. And therefore, that's what makes me more cautiously optimistic," he says. "But clearly, we need to wait for the data."

The public health community has known about omicron only for a few weeks, but already Pfizer and Moderna are springing to action to study potential omicron shots — just in case they're needed.

Pfizer CEO Albert Bourla told The Wall Street Journal on Tuesday that the company could have an omicron-specific vaccine ready by March.

A rise in COVID-19 hospitalizations would be a warning

When will it be clear if a new vaccine is needed?

Slaoui remembers talking with colleagues at the National Institute of Allergy and Infectious Diseases about how to respond to new variants. "It will be very important to have pre-established criteria with what triggers the fact that we start immunizing people again," he says.

To him, that trigger is if the hospitalization rate among people who are vaccinated is significantly higher with a new variant than it was with the previous variant, because ultimately the vaccine is meant to reduce severe disease, rather than prevent every case of COVID-19.

Norman Baylor, a former director of the Food and Drug Administration's Office of Vaccines Research and Review, agrees it's still not clear whether omicron will be too much for current vaccines. But if an omicron booster is needed, the FDA's handling of boosters offers clues as to how it would handle an omicron-specific shot.

"They required some clinical data ... immunogenicity data or antibody response data in individuals who had received the other vaccines," says Baylor, now the president and CEO of Biologics Consulting.

Because this is a new variant, the agency may require a little more data this time around. "And so that's something that needs to be determined," Baylor says. "What additional information do we need to be comfortable?"

Still, it shouldn't take as long as it took Operation Warp Speed and its member companies to research the original COVID-19 vaccines.

This is where the mRNA technology used in the Pfizer-BioNTech and Moderna COVID-19 vaccines comes in. With an mRNA vaccine, it's easier to switch to a new variant than it would be with other kinds of vaccines. "The beauty of the technology is that it's so flexible," Slaoui says.

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