Healthcare workers are now among those eligible to receive a COVID-19 booster shot, as the FDA on Sept. 22 granted emergency use authorization for a booster dose of Pfizer's COVID-19 vaccine for Americans who are ages 65 and older, have a job that increases their risk of infection and are at high risk of severe COVID-19.

Five things to know:

1. Those who are eligible may receive a Pfizer booster shot at least six months after their second dose.
   
   
2. Acting FDA Commissioner Janet Woodcock, MD, said the country's booster strategy is subject to change as more data becomes available on COVID-19 vaccines' protection over time. The booster rollout will likely be staggered, starting with the populations deemed most vulnerable.
   
   Dr. Woodcock said the FDA is prioritizing healthcare workers, teachers, day care staff, grocery workers and those in homeless shelters or prisons due to their institutional or occupational exposure to COVID-19.
   
   
3. The CDC's Advisory Committee on Immunization Practices will hold a meeting Sept. 23 at which they will decide who falls under the category of people who are at high risk of severe COVID-19.
   
   
4. The FDA has not explicitly addressed when or if the millions of Americans who received COVID-19 vaccines made by Moderna and Johnson & Johnson will be eligible for booster doses. The agency still needs to review data produced by those drugmakers.
   
   
5. About 22 million Americans received their second Pfizer dose at least six months ago, according to the CDC. About half of them are 65 and older. 

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