A Food and Drug Administration advisory panel voted Thursday to recommend Moderna booster shots for emergency use authorization, bringing millions of people in the U.S. one step closer to being eligible for additional doses.
The panel, called the Vaccine and Related Biological Products Advisory Committee, voted unanimously in favor of authorizing the shots. The decision will go to the FDA, which is expected to make a final ruling in the coming days.
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The panel’s recommendations followed the blueprint it established last month for booster shots of Pfizer-BioNTech’s vaccine: For people who were initially vaccinated with Moderna, the booster would be authorized for adults ages 65 and up, people in long-term care facilities and people ages 18-64 with underlying medical conditions and who are at high risk of exposure to the coronavirus because of their job. Such people would be eligible at least six months after their second shots.
Moderna’s booster dose would be given as a half-dose of 50 micrograms, compared to the 100 micrograms given in the initial vaccination series. (By contrast, Pfizer’s booster is the same 30-microgram dosage as its initial series.)
Jacqueline Miller, the therapeutic area head for infectious diseases at Moderna, said in her presentation to the committee that the company chose the half-dose because it wanted to use the lowest dose possible needed to induce an immune response.
Miller noted that using a lower-dose booster has worked well for other vaccines, including the DTaP vaccine, which protects against tetanus, diphtheria and whooping cough.
The meeting was less contentious than the group’s discussion last month about Pfizer, when the advisers rejected authorizing Pfizer boosters for all adults 18 and up six months after their initial vaccinations and instead opted to limit eligibility.
In a discussion after the vote, the panel largely agreed that boosters were not yet needed for the broader population, which would include all adults 18 and up.
The younger population appears to be responding quite well to the vaccines, and protection is holding up, said Dr. Michael Kurilla, an infectious disease expert with the National Institutes of Health. "I don’t necessarily see the need for a sort of 'let it rip' campaign for boosters for everyone who’s ever been vaccinated."
The case for Moderna
Data shows that protection from Moderna’s vaccine has waned: People who were vaccinated earlier in the year were more likely to have breakthrough infections compared to people who were vaccinated several months later, Miller said. Nearly all of the breakthrough infections were caused by the delta variant.
Several of the breakthrough cases were considered severe, and two people died.
"We are concerned about the breakthrough disease that we’ve been observing" in the participants in the original clinical trial, Miller said, "and particularly the breakthrough cases that we’re starting to see in severe disease in the older adults."
The booster dose led to higher antibody levels, including antibodies against the delta variant.
Still, a handful of breakthrough infections — 20 cases — were reported among people who received boosters.
Dr. Doran Fink, a deputy director of the FDA’s division of vaccines, said it’s still unknown what levels of antibodies are needed for protection.
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Both Moderna’s presentation and the FDA’s analysis found the booster to be safe, although several committee members said they wanted to see more safety data from the company.
Side effects from the booster were similar to those seen after the second dose. They included arm pain, fatigue, headache and muscle aches.
However, the booster trial didn’t include enough participants to evaluate whether the extra dose raised the risk for myocarditis, Fink said.
Myocarditis, or inflammation of the heart muscle, has been linked to both Moderna’s and Pfizer’s Covid-19 vaccines. The condition is rare and mostly commonly seen in men under 30.
Hui-Lee Wong, the associate director for innovation in the FDA’s Office of Biostatistics and Epidemiology, said myocarditis occurred in similar rates following the second doses of both vaccines.
In data from Israel, where 3.7 million people have gotten Pfizer booster shots, 17 cases of myocarditis were reported, said Dr. Sharon Alroy-Preis, the director of public health services for Israel’s Health Ministry, who presented Thursday.
"The rate of it is really, really low compared to what you would have expected, if it was the same rate as after the second dose," she said. "Perhaps it’s because we’re giving this dose five months or later" as opposed to giving two doses three weeks apart.
The same group of advisers will convene Friday to discuss a booster shot of Johnson & Johnson’s Covid vaccine. It will also review the results of a National Institutes of Health study of "mixing and matching" Covid vaccines. The study found that giving people who initially received the Johnson & Johnson vaccine booster doses of either Pfizer’s or Moderna’s vaccine led to a stronger immune response than a second Johnson & Johnson dose.
Next week, a group of advisers to the Centers for Disease Control and Prevention will take up the question of who should receive the Moderna and Johnson & Johnson booster shots. If the boosters are recommended, the CDC director, Dr. Rochelle Walensky, would then sign off, and shots could start going into arms.
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