Some experts questioned whether Moderna had collected enough data about possible side effects. Regulators and scientists are particularly concerned about the risks of the heart disease myocarditis, or inflammation of the heart muscle, and pericarditis, or inflammation of the lining around the heart.
The FDA added warnings about those risks to its Pfizer-BioNTech and Moderna vaccines in June, and officials Thursday cited an increased risk in men ages 18 to 25 who were fully vaccinated with Moderna or Pfizer-BioNTech.
A key part of Thursday’s discussion revolved around Israel’s booster campaign for the Pfizer-BioNTech vaccine. The Biden administration has been closely monitoring Israel’s experience, as the country has a nationalized health care system that allows it to closely monitor vaccine recipients.
A senior Israeli health official told the commission that her government’s booster campaign had changed the course of the pandemic there. She said Israel saw dramatically lower rates of both infection and serious illness in those who received a booster injection compared to those who did not. However, it was not clear whether other factors, such as the demise of the Delta variant, were also of influence.
dr. Mark Sawyer, a professor at the School of Medicine at the University of California at San Diego, said that while the Moderna vaccine was different, Israel’s data was compelling.
But dr. Kurilla of the National Institutes of Health wondered if Israel’s booster campaign deserved such praise, noting that the latest drop in the infection rate in the country seemed to fit with previous waves of the virus.
He asked Dr. Sharon Alroy-Preis, Israel’s director of public health services, said whether she believed a third injection of Pfizer’s vaccine would extend protection for a long time, or that “you’ll be back in six months” for another booster.
dr. Alroy-Preis noted that some vaccines provide years of protection after a booster shot. Whether that’s true for coronavirus vaccines, she said, is “a million dollar question.”