(CNN) -- Vaccine advisers to the US Food and Drug Administration are meeting Thursday to discuss whether to authorize boosters of Moderna's coronavirus vaccine for some adults.
It's the first portion of a two-day Vaccines and Related Biological Products Advisory Committee meeting that will also include a vote on boosters for the Johnson & Johnson vaccine and a presentation on mix-and-match vaccines. Thursday's agenda focuses on Moderna boosters and includes a presentation by Moderna, and another by the FDA, which will provide its assessment of Moderna's booster data.
Moderna is requesting authorization for 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 request mirrors 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.
Thursday's VRBPAC meeting, which will be streamed online, is scheduled to last until 4:45 p.m. ET. Two hours for discussion and voting is scheduled to begin at 2:45 p.m. ET.
On Thursday, the committee heard from Dr. Peter Marks, the director of FDA's Center for Biologics Evaluation and Research who recently took over as acting director of the agency's Office of Vaccines Research and Review as two of its senior leaders prepared to depart the agency.
They also heard from Israeli researchers who had previously spoken in support of Pfizer's booster application.
Most people in Israel received the Pfizer vaccine, and the country began rolling out boosters well ahead of the United States. Dr. Sharon Alroy-Preis of Israel's Ministry of Health told the FDA advisers on Thursday that as it began to offer booster doses to more age groups, the percentage of positive Covid-19 tests dropped to 2.6%, and the overall incidence of severe cases declined.
"The booster dose in Israel was effective and so far, has a safety profile similar to the other doses," Alroy-Preis said.
"We have improved protection against confirmed infection for all ages 16 and above. We have improved protection against severe disease in ages 40 and above," Alroy-Preis said. "It could impact even younger than 40 years old for severe and critical disease and mortality."
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 US 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.
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