The Food and Drug Administration on Tuesday authorized second booster shots of the Moderna or Pfizer COVID-19 vaccines for adults 50 and older and for some immunocompromised people. Both groups can get the additional shot four months after their first booster.
Noting evidence of waning immunity among the first booster shots, Dr. Peter Marks, FDA’s vaccine chief, said in a briefing Tuesday that the additional booster “will help save lives and prevent severe outcomes among our highest risk patients.”
But reaction within the medical community was mixed to the FDA’s announcement. Some said the second booster is not needed just now, pointing to the much lower numbers of COVID-19 cases, hospitalizations, and deaths in many parts of the country.
“The data supporting a fourth shot are really quite limited at this point. It is not clear that there is much of a benefit,” said Dr. Dan Barouch, director of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center. “And given that we are not in a surge right now, the timing may be wrong.”
But Dr. Sandra Nelson, an infectious disease doctor at Massachusetts General Hospital, said the additional booster will be helpful to some people, pointing to the abundant evidence of waning immunity four to six months after the first booster, leaving many early adopters less protected against the virus.
Making a fourth dose available, she said, “gives individuals and their provider another option to consider based on their own level of concern or risk, but it may not be something that needs to be rolled out widely.”
Yet, while some people are pining for additional shots, just 44.8 percent of all fully vaccinated people have gotten their first booster. Demand for them peaked between Thanksgiving and Christmas, and has fallen steadily since January.
“I wouldn’t be surprised if the uptake of this fourth dose is even less,” said Barouch.
The second boosters contain the same ingredients as the original COVID vaccines. Although Cambridge-based Moderna and Pfizer have both designed booster shots tailored to the Omicron variant, those versions are still in clinical trials. And, since infections are relatively low throughout most of the country, some doctors say it makes sense to hold off on a second booster until the new Omicron-specific shots are available, or at least until there is another surge.
“I think it would be safe to take another booster right now,” said Dr. Shira Doron, an infectious disease physician and hospital epidemiologist at Tufts Medical Center. But Doron isn’t convinced the timing is optimal. If you get a second booster now, “you might not be eligible for something better or at a more important time,” she said.
A more contagious version of Omicron, the BA.2 subvariant, has become the dominant form of COVID-19 in the United States, which may have contributed to the FDA’s authorization of a second booster. The new variant has led to surges of cases in China and Europe, and scientists are watching closely to see if it causes a second wave of Omicron infections in the United States, too.
“We don’t know how significant the BA.2 wave will be, but we are seeing signs that cases are going up,” said John Brownstein, an infectious disease epidemiologist at Harvard Medical School and chief innovation officer at Boston Children’s Hospital. “There is not a lot of downside to getting a second booster, so giving people the option is important.”
“The calculation is probably different if you recently were infected with Omicron,” Brownstein added. In that case, “it probably makes sense to wait.”
Many doctors said that they would recommend the second booster for people most at risk of developing severe COVID-19 symptoms. “For people 80 and above I would strongly recommend it,” said Dr. Paul Sax, clinical director of the division of infectious diseases at Brigham and Women’s Hospital. He also recommends the second booster for people over age 50 with medical problems such as diabetes, high blood pressure, and obesity.
“What is not so clear is if it makes sense for a healthy 55-year-old,” he said.
The FDA also said that some immunocompromised people could get a second booster — a fifth shot in total for them, since their initial vaccination series included three shots, plus a more recent booster. That fifth shot is authorized for people 12 and up for Pfizer’s vaccine, and people 18 and up for Moderna’s vaccine.
In mid-February, the Centers for Disease Control and Prevention said that the Moderna and Pfizer vaccines were 91 percent effective at preventing hospitalizations two months after the first booster dose, but effectiveness dropped to 78 percent at four months. The booster shot’s ability to prevent emergency department or urgent care visits also dropped from 87 to 66 percent during the same time period.
Dr. Walter Orenstein, associate director of the Emory Vaccine Center in Atlanta, said the data on waning protection against severe disease may have played a role in the FDA’s authorization of a second booster. “As long as the safety signals are fine, I think I’d rather get it than not get it,” he said.
Moderna said the FDA authorization was based on data from Israel, which has already been offering second booster shots this year. One study found that a second booster is 73 percent effective at preventing severe disease throughout the nine weeks of the study. But other studies provide less strong evidence in favor of the second booster.
A study of health care workers in Israel found that a second booster raised waning antibody levels to similar levels detected after the first booster dose. But the second booster provided only marginal protection against infection from Omicron, and the study was too small to conclude whether it increased protection against severe disease.
But any hesitancy that some medical experts are expressing over the second booster does not apply to the first booster.
“That third shot is really critical, and not enough people are getting that message,” said Dr. Sabrina Assoumou, an infectious disease physician at Boston Medical Center and professor at Boston University School of Medicine.
“We need to try our best to vaccinate the unvaccinated, that is what would benefit us most at this point,” she added.
Doctors were surprised that the FDA authorized a second booster without its normal process of letting its independent vaccine advisory committee discuss and debate the available evidence in a public forum. Normally, that advisory committee “analyzes every shred of data” before the FDA makes its decision to authorize a vaccine, Doron said. The advisory committee is scheduled to meet next week.
Following the FDA authorization, a CDC committee will meet to make more specific recommendations about who should get a vaccine. That will arm doctors with information to have nuanced conversations with patients about the risks and benefits of vaccines.
“In the absence of both those meetings, I am going to struggle to advise people,” Doron said. “I don’t understand the underlying motivation for doing things out of order.”