Moderna had asked for emergency use authorization for a half dose of its vaccine to be used as a booster for certain people.
All 19 members of the FDA's Vaccines and Related Biological Products Advisory Committee supported authorizing a 50-microgram booster dose — half the size of the 100-microgram doses used in the primary series of the two-dose vaccine — at least six months after the second dose, and only for certain groups: people age 65 and older; people ages 18 to 64 who are at high risk of severe COVID-19; and people ages 18 to 64 whose exposure to the coronavirus in their settings or jobs put them at risk for COVID-19 complications or severe illness.
Moderna's EUA request mirrored the groups authorized to receive a booster dose of Pfizer's mRNA vaccine. Third doses of the Moderna and Pfizer COVID-19 vaccines are already authorized for some immunocompromised people.
Members of the committee said they were not entirely convinced the data showed a booster was necessary or that it increased protection.
"The data are not perfect but these are extraordinary times and we have to work with imperfect data," said Dr. Eric Rubin, editor-in-chief of the New England Journal of Medicine and a professor at the Harvard T.H. Chan School of Public Health.
"We can't afford to have health care workers, even if not sick, be positive and infected and have to stay home from work because in parts of the country there's a shortage of health care workers and there's burnout everywhere," said Dr. Stanley Perlman, a professor of pediatrics at the University of California San Diego.
The Vaccines and Related Biological Products Advisory Committee meeting will continue Friday, when members are expected to vote on boosters for the Johnson & Johnson vaccine, and will hear a presentation on mix-and-match vaccines, according to the report.
The FDA's committee of independent advisers typically discusses and makes recommendations to the agency around vaccine authorizations and approvals, and the agency then makes the final decision about whether to OK a vaccine.
If the FDA gives emergency use authorization to Moderna boosters, vaccine advisers to the Centers for Disease Control and Prevention will meet to discuss which groups to recommend them to. Typically, shots can be administered once the CDC director signs off on the recommendation.
CDC's Advisory Committee on Immunization Practices is already scheduled to meet to discuss boosters from 10 a.m. to 5 p.m. ET October 20-21.