WASHINGTON — Federal regulators authorized second booster shots of the Pfizer-BioNTech and Moderna coronavirus vaccines on Tuesday for everyone 50 and older, describing the move as an effort to bolster waning immunity against severe disease in case the virus sweeps the nation again in the coming months.
The Food and Drug Administration said people in the age group could get the additional shot at least four months after their first booster. The agency also authorized a second booster for people 12 and older with certain immune deficiencies.
The decision means that tens of millions of Americans are now eligible for what would be their fourth shot. And even though the public may be tiring of repeated doses, the move is most likely an interim one: Federal health officials say it is quite possible that Americans of all ages may need another shot in the fall to prepare for any winter surge. The hope is that by then, scientists will have reconfigured the existing vaccines to work better and last longer against the variants that have emerged since November.
Federal health officials initially considered limiting second boosters to those at least 60 or 65 years old. But at a news briefing, Dr. Peter Marks, who oversees the F.D.A.’s vaccine division, said a lower age limit made more sense because so many Americans over 50 have chronic medical conditions that put them at risk.
While a single booster dose continues to protect most Americans from hospitalization and death due to Covid-19, he said, those 50 or older who got their first booster more than four months ago “should seriously consider getting another.”
The Centers for Disease Control and Prevention was a bit more circumspect. In the fall, when the first round of boosters was authorized, the agency cited a clear benefit from an added shot.
On Tuesday, in contrast, the C.D.C. updated its vaccine guidance to note that second boosters were now allowed. Dr. Rochelle P. Walensky, the agency’s director, said the option of another dose was “especially important for those 65 and older and those 50 and older with underlying medical conditions that increase their risk for severe disease from Covid-19 as they are the most likely to benefit from receiving an additional booster dose at this time.” About one-third of people aged 50 to 65 have significant medical conditions, officials said.
The F.D.A. made the decision with very limited data, largely from Israel. Experts said there was fairly robust data showing a need for stronger protection now that variants have cut into the vaccines’ potency. There is significantly less data on whether a second booster will provide that protection, and for how long. Regulators said another dose posed no new safety concerns.
The idea that just six months after federal regulators authorized the first round of boosters, another booster is already necessary could add to public fatigue with Covid vaccines. The evidence now suggests that the government’s decision last fall to authorize a first booster — the subject of much scientific debate at the time — saved lives over the winter. While the Omicron variant surged, those who were boosted were 21 times less likely to die from Covid and seven times less likely to be hospitalized than those who were unvaccinated, according to the C.D.C.
But at this point, “each additional dose is offering marginal value,” said Dr. Eric Rubin, an infectious diseases expert at the Harvard T.H. Chan School of Public Health. At an event hosted by Columbia University this week, Dr. Kate O’Brien, the director of the vaccines department at the World Health Organization, said, “We’re in a relatively weak position on the sort of policy front around exactly what the data are that are compelling decisions about fourth doses.”
The strongest data in support of a second booster came from a newly released Israeli study that has not yet been peer reviewed. During a 40-day period this year, the researchers studied Covid death rates among more than half a million adults 60 to 100 years old who had received at least one booster.
Among the 234,868 who had only one booster, 232 people died of Covid. Among the 328,597 people who got a second booster, 92 died of Covid. The mortality rate “was significantly lower among those who had received an additional booster,” the researchers said.
Federal officials also studied statistical models that suggested that if the virus surged again in late spring or summer, a second booster could save thousands of lives and prevent tens of thousands of hospitalizations.
The C.D.C. singled out Johnson & Johnson recipients for special treatment. The agency has already recommended Moderna’s and Pfizer’s vaccines over Johnson & Johnson’s for safety reasons.
On Tuesday, it said adults who got an initial dose plus a booster of Johnson & Johnson’s vaccine at least four months ago — a group that could include more than 1.4 million people — were eligible for a second booster with one of the mRNA vaccines. The agency cited new data that showed Johnson & Johnson’s vaccine was less effective than the other two.
Both Pfizer and Moderna have argued for a second booster. Pfizer and BioNTech have said data collected during the Omicron wave showed that the potency of their initial booster wanes within three to six months against both symptomatic infection and severe disease. Data from Israel suggests a second booster restores protection, but researchers have not tracked the recipients of those boosters for long.
Dr. Paul Burton, Moderna’s chief medical officer, told CNN on Monday that the virus’s mutations had weakened the vaccines’ shield. “The only way that we’re going to get to a period of stability and ultimately to an endemic disease is to keep people protected, keep their antibody levels up, and I’m afraid that means regular boosting,” he said.
Both Pfizer and Moderna have an obvious financial incentive to promote more shots: They are projecting tens of billions of dollars in Covid vaccine sales this year alone.
Neither the F.D.A. nor the C.D.C. convened its outside committee of experts to debate the new policy, sparking criticism. Dr. Rubin, an F.D.A. panel member, called that decision reasonable but said it was critical for the agency to make public any data it relied upon for others to scrutinize. The F.D.A.’s decision memo is expected to be posted online soon.
Like other experts, Dr. Rubin said what is really needed now is a vaccine that works better than the existing ones against the new variants. Many studies are now underway to find it, but the earliest results are not expected until later this spring.
“It’s not actually clear yet what the optimal booster should be,” Dr. Marks said.
The F.D.A. panel is scheduled to meet on April 6 to discuss what the nation’s booster strategy should be moving forward. Federal health officials have suggested that shots in the fall could be needed, just as they are for the flu. “At some point,” Dr. Marks said, “we’re going to have to realize that this is a virus that’s going to be with us and that we have to come to grips with dealing with it on a regular basis.”
Another major decision looms, possibly next month, when the F.D.A. may rule on whether to authorize a vaccine for the nation’s youngest children — the only group still ineligible for shots. Moderna plans to submit data in the coming weeks from what it has described as a successful clinical trial of a two-dose regimen for children under 6. Pfizer and BioNTech have said they expect results from their three-dose trial next month for children under 5.
Dr. Marks said on Tuesday that the F.D.A. would seek input from its advisory committee before making decisions on shots for the youngest children.
For many of the roughly 3 percent of Americans with immune deficiencies, Tuesday’s decision authorizes what would essentially be a fifth dose. Those 12 and older can get Pfizer’s shot, while those adults can pick between Pfizer’s and Moderna’s.
How much public demand there is for another booster is unclear. With the pandemic in a lull, the nation’s enthusiasm for shots has been flagging. New reported infections have been falling since the third week in January, when the Omicron wave peaked.
According to C.D.C. estimates on Tuesday, an even more contagious subvariant of Omicron, known as BA.2, is now dominant among new U.S. cases. The subvariant has led to a surge of new cases in Europe. But some experts think the United States may escape the brunt of its impact, partly because the Omicron variant infected so many Americans.
Cheryl Shell, a 71-year-old retiree in the town of Spring Arbor in southern Michigan, said she was not waiting around to find out. She got her first booster in November, she said, and she is eager to get a second because she is concerned about waning potency. “I’ve got to go for any protection I can get,” she said.
Kate Bedingfield, the White House communications director, said the new authorization “is a good thing and it is a straightforward thing.” She said the government had plenty of supply to offer second boosters to those now eligible.
But she reiterated a point the White House has made repeatedly in recent weeks: If booster shots are recommended for the general population, she said, Congress will have to provide more money to pay for them.
Noah Weiland and Adeel Hassan contributed reporting.