When would I need to get it?
Eight months after your second Pfizer or Moderna shot. If the F.D.A. authorizes a third dose, the first booster doses will be available on Sept. 20.
Health care workers, nursing home residents and other older Americans — the first to receive the vaccines — will be the first in line for boosters.
Officials are likely to recommend that people get a third dose of the same vaccine they initially received.