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WASHINGTON — Whether Americans will need additional vaccines specifically tailored to the rapidly spreading Omicron variant of the coronavirus may depend on how long it circulates in the United States, a top regulator told STAT in an interview Wednesday.

If it turns out that Omicron is the new variant that actually things settle into, well then of course we will probably need an Omicron-specific vaccine,” said Peter Marks, the Food and Drug Administration’s top vaccine regulator.On the other hand, if this is just a variant that’s passing through and we get [a new variant] in a month or two, we won’t need that.”

Marks added that Omicron is “a very, very fast-moving virus” that “could pass across this country within a matter of a few weeks,” and that he does not know for sure whether Omicron-specific jabs will be needed. 

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The Omicron variant now accounts for an estimated 73% of all Covid-19 cases diagnosed in the United States, according to recently released data from the Centers for Disease Control and Prevention. Omicron cases made up just over 12% of cases during the second week of December. Recent reports suggest the variant causes milder disease compared to the previously dominant Delta variant, though experts have cautioned it is too early to say so definitively. 

All three manufacturers with vaccines authorized in the United States — Pfizer, Moderna, and Johnson & Johnson — are currently readying Omicron-specific vaccines. Pfizer has said it could begin delivering its Omicron-specific vaccine by March, pending FDA approval. 

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Dr. Peter Marks
Peter Marks is the director of FDA’s Center for Biologics Evaluation and Research Michael J. Ermarth/FDA

Marks emphasized that vaccine makers’ efforts to develop Omicron-specific shots do not guarantee such vaccines will ever be administered. 

“Vaccine manufacturers are all proceeding at risk to make, and get ready to study, Omicron-specific vaccines. But whether we will really ever need to deploy those, I am not certain yet,” Marks said. “Remember we’ve been through this exercise … at one point we were worried about a South African variant — the Beta — and then it became the Delta … and now we have Omicron.”

Calls for an Omicron-specific variant have prompted debates within the Biden administration and more broadly among public health experts. 

The Biden administration has signaled that it plans to fight the spread of Omicron through existing booster shots, which were not formulated specifically for Omicron. Early data suggest that the booster shots from Moderna and Pfizer significantly enhance protection against the Omicron variant. 

“Our doctors have made it clear: Booster shots provide the strongest of protection,” President Biden said in a speech Tuesday afternoon. “People with booster shots are highly protected. Join them. Join us.” 

Anthony Fauci, the head of the National Institute of Allergy and Infectious Diseases and the chief medical adviser of the Biden Covid-19 response, has expressed doubts about the need for Omicron-specific shots.

“I’m not so sure that we’re going to have to get a variant-specific boost vaccine to get an adequate protection from Omicron,” he told STAT. “Because if you look at protection against variants, it appears to relate to the level of immunity and the breadth of the immunity that any given vaccine can instill on you.”

The World Health Organization has also set up a technical advisory group to think about the potential for changes in the strain composition of Covid-19 vaccines, though the group’s top officials have cautioned that creating an Omicron-specific vaccine might hamper efforts to fight other strains of the virus.

“If we lurch into producing Omicron-specific vaccines, we could lose effectiveness against currently circulating strains,” said Mike Ryan, head of the WHO’s health emergencies program. “We have to be fast enough to make a good decision, but at the same time, we have to be able to consider all of the relevant data.”

The rise of Omicron has also prompted some experts to call for the development of a so-called pan-coronavirus vaccine, which would be effective against multiple strains of the virus. 

“We don’t know yet if it will be possible, but I don’t think vaccines we have now will be the mainstay vaccines in the years to come,” said Michael Osterholm, the director of the Center for Infectious Disease Research and Policy at the University of Minnesota and a former adviser on Biden’s Covid-19 response team. 

Osterholm’s center is currently developing a “road map” for developing such a vaccine, with funding from the Bill and Melinda Gates and Rockefeller foundations. 

If variant-specific vaccines are needed, the FDA will rely on an abbreviated review process focused largely on testing the vaccines’ immune responses, known as immunogenicity — even if the vaccines are bivalent or multivalent, meaning they are designed to protect against multiple strains of Covid-19.

“We would probably mainly be looking at immunogenicity-based studies … whether it be for a monovalent [vaccine], or a bivalent, or multivalent vaccine,” Marks said. “We would not expect to see a repeat of a full clinical development program.”

Megan Molteni and Helen Branswell contributed reporting.

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