COVID-19 Vaccine Tracker
September 22, 2021 9:02 PM EDT

The U.S. Food and Drug Administration (FDA) on Sept. 22 authorized booster doses for certain people already vaccinated against COVID-19 but at high risk of infection, including those over age 65 and those who are more likely to get exposed to the disease, such as health care, frontline, emergency and transportation workers, among others. The booster authorization only applies to Pfizer-BioNTech’s COVID-19 vaccine.

“After considering the totality of the available scientific evidence and the deliberations of our advisory committee of independent, external experts, the FDA amended the Emergency Use Authorization (EUA) for the Pfizer-BioNTech COVID-19 vaccine to allow for a booster dose in certain populations such as health care workers, teachers and day care staff, grocery workers and those in homeless shelters or prisons, among others,” said Dr. Janet Woodcock, acting FDA commissioner in a statement announcing the FDA’s decision. “As we learn more about the safety and effectiveness of COVID-19 vaccines, including the use of a booster dose, we will continue to evaluate the rapidly changing science and keep the public informed.”

The agency’s decision follows the advice of its advisory committee, which met on Sept. 17 to review data on Pfizer-BioNTech’s booster, and voted unanimously to authorize an additional dose for certain populations. The FDA’s decision now goes to the Centers for Disease Control’s (CDC) Advisory Committee on Immunization Practices to provide details on how long people who have already been vaccinated must wait before getting a booster, and whether the booster should only be given to people who were originally vaccinated with the Pfizer-BioNTech shot, which is likely.

The data that Pfizer-BioNTech presented to the FDA showed the booster dose was both safe and efficacious in increasing waning immune responses to the vaccine. In the companies’ studies involving several hundred people who received the recommended two doses of the vaccine, antibody levels against the COVID-19 virus started to fall after several months. But boosting with third dose of the vaccine about six months after the second shot brought antibody counts back up, in some cases to levels even higher than those generated after the second dose. The FDA also reviewed data from Israeli health agencies, which showed early evidence that booster doses reduced infection rates among people over 60 years by 10-fold compared to those who received only the two original doses, and that the additional dose brought antibody levels up to where they were just after the second dose.

There are less robust data on people in younger age groups, since anyone in that category who has been vaccinated received their shots more recently than the elderly, who the FDA prioritized to receive the Pfizer-BioNTech vaccine first, after the agency authorized the two-dose shot in Dec. 2020. That’s why the advisory committee voted against recommending a booster for all vaccinated people, as Pfizer-BioNTech originally requested, and limited its recommendation to high-risk populations.

Studies looking at people who were originally vaccinated with Moderna or Johnson&Johnson-Janssen’s shot and received a different booster dose are expected soon, but were not available for health officials at FDA or CDC to review yet.

“This first FDA authorization of a COVID-19 vaccine booster is a critical milestone in the ongoing fight against this disease,” said Albert Bourla, chairman and chief executive officer of Pfizer, in a statement. “Today’s FDA action is an important step in helping the most vulnerable among us remain protected from COVID-19.”

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