New omicron-targeting coronavirus booster shots are poised for rollout after being authorized Wednesday by the Food and Drug Administration — a move designed to improve protection against severe illness and death during a potential rise in covid-19 cases this fall and winter.
The emergency authorizations of the boosters — one by Moderna and the other by Pfizer and its German partner, BioNTech — mark the start of a high-stakes effort by the Biden administration to deploy a more muscular defense against a virus that has evolved drastically over the last 2½ years and is still killing an average of 400 to 500 people a day in the United States. The changes are the first since the mRNA vaccines debuted in December 2020.
“These updated boosters meet the FDA’s rigorous standards and are expected to help restore immune protection against covid-19,” FDA Commissioner Robert M. Califf said in a call with reporters.
Still unclear is whether the American public, which has been slow to embrace boosters, will show more enthusiasm for the newest crop of shots, which will be free to the public. Some experts, including Paul A. Offit, one of the FDA’s most prominent vaccine advisers, have criticized the agency for moving too quickly, saying it is not clear that the new booster is better than the current shot. And others say the FDA’s lack of human data on the shots’ effectiveness — it is relying heavily on mouse studies — could fuel skepticism.
“We already have a problem with booster acceptance,” Eric Topol, professor of molecular medicine at Scripps Research, said. While praising the FDA’s desire to move aggressively against the virus, he said the paucity of human data for the new shots could make people wary. “I think that would be unfortunate,” he said.
Peter Marks, top vaccine official at the FDA, defended the agency’s approach, saying on the news call that the agency “is very confident” in the new boosters. He said the mRNA vaccines have been administered to billions of people worldwide, have a strong safety record and are well-understood by scientists.
On effectiveness, he said, officials believe that matching the boosters to the variants that are circulating “will restore the kind of protections we saw when the vaccines were first launched.” Although coronavirus cases are decreasing now, he said, some experts worry there could be a sharp rise in infections around Thanksgiving, as people flock indoors and immunity continues to wane.
Human data on the updated boosters is at least one to two months off, and delaying the deployment of retooled boosters until then could be too late to counter a potential surge, Marks said. He also said the retooled shots could better protect people from “long covid,” an unexplained constellation of symptoms that includes fatigue, memory loss and chest pain.
The new bivalent boosters include components aimed at the variants and the original virus, which has long disappeared. Including a component from the initial vaccine “hedges our bets” because it has remained effective against serious illness and death, even as it has lost its punch in preventing infection and transmission in the omicron era, said Ofer Levy, director of the Precision Vaccines Program at Boston Children’s Hospital and another FDA vaccine adviser.
The BA.5 variant now accounts for almost 90 percent of cases in the United States, according to the CDC. Reported cases have dropped below 100,000 a day, on average, but the numbers don’t capture many of the home coronavirus tests being used.
The revised boosters show how mRNA vaccines can be redesigned quickly to counter new variants, with production scaled up swiftly; the FDA did not settle on the revised formula until late June. Vaccines that would represent a sea change in approach — such as shots to counter all coronaviruses and their variants, perhaps by a nasal spray — are years away, experts say.
The FDA cleared the new Pfizer-BioNTech booster for people 12 and older and the Moderna shot for those 18 and up, and the CDC is expected to concur that those ages are appropriate. Anyone who has received the two-shot primary series of the mRNA or Novavax vaccines and the single-shot Johnson & Johnson vaccine will be eligible, regardless of whether they received any booster shots. Agency officials expect pediatric data on the new boosters in the next month or two and could authorize the shots for children later this year.
People who recently received an initial vaccine shot or a booster should wait at least two months before getting the new booster, the FDA said. Getting the shot too soon after a previous booster could blunt its effectiveness or increase the possibility of a rare side effect, officials said. People can get the updated vaccine at the same time they get their flu shot, officials said.
The data used by the FDA to authorize the shots has sparked sharp debate. FDA officials said they cleared the boosters on the “totality” of the evidence, which included human studies of earlier experimental bivalent shots — including one that generated virus-fighting antibodies against BA.1, the first omicron subvariant — and the overall record of the shots since December 2020.
The FDA also considered mouse data on the new booster, concluding the omicron-targeting shots generated a strong antibody response against the variants. Moderna said it has started a human trial on the updated shot, and Pfizer and BioNTech said recently they were about to begin such a study.
Agency officials said they have relied on animal studies for years in making annual adjustments to the influenza vaccine.
“These are not hugely different protein products, and our folks are very comfortable with the change that has been made here, as am I,” Marks said in an interview before the authorizations.
Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases, agreed, saying the updated boosters will be helpful even if an “out of left field” variant emerges that is different from BA.4 and BA.5.
“Any boost of immunity will have some degree of cross-reactivity even against a new variant,” Fauci said.
But some scientists said the coronavirus boosters are not comparable to the influenza vaccines because the new pathogen has been around only for a few years while flu has been circulating for decades.
Michael T. Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, said he wished human data was available right away.
“The mouse data are helpful,” Osterholm said, “but the reason to have data for humans is to say the immune response is as good or better” as the one triggered by the original vaccine or an alternative.
“I don’t see the urgency here,” Osterholm said, noting the decline in covid cases. “We don’t have data to support that the BA.4/BA.5 vaccine is superior.”
Peter Hotez, professor of pediatrics and molecular virology and microbiology at Baylor College of Medicine, also worried that the lack of human data could discourage some people from getting the new booster.
“With a very skittish public that has voted with its feet about taking boosters, if we could add layers of reassurance that [the shot] has gone into humans for some level of studies, that would help,” Hotez said.
Fewer than half of the people in the United States have received a single booster shot, according to the CDC.
But Jeanne Marrazzo, director of the infectious-diseases division at the University of Alabama at Birmingham, endorsed the authorization of the new booster.
“The FDA is doing the right thing now in the face of winter and evolving variants,” Marrazzo said. “Most people who have taken care of patients are freaking out about what might happen in the fall and saying, ‘How can you not do something?’ ”
Levy, of Boston Children’s Hospital, agreed.
“As fall and winter arrive, we will likely see [deaths from covid] rise to 1,000 or more a day, and that is not trivial,” Levy said.
Federal officials and their advisers have been debating the composition of the new boosters for months. In late June, the FDA’s independent vaccine experts voted 19-2 to include an omicron-based component in the fall boosters. The FDA subsequently directed manufacturers to include components that targeted BA.4 and BA.5, arguing such shots would be the best match for the circulating virus. The old formulation will not be available as boosters any more.
At the same time, the FDA said it was not ordering a change in the vaccine for the initial vaccination series because the original formula provided a “base of protection against serious outcomes” caused by circulating strains of the virus.
The U.S. government has bought more than 170 million doses of the boosters, but initially about 10 million to 15 million doses a week will be available, officials said.
Now that the vaccines have been authorized, the boosters can be shipped to states and vaccine sites. But the shots cannot be administered until the CDC recommends their use.
Joel Achenbach and Lena H. Sun contributed to this report.