The Food and Drug Administration has authorized a second booster dose of either the Moderna or Pfizer-BioNtech COVID-19 vaccine for older people and certain immunocompromised individuals.

The second booster may be given to people who are 50 and older or immunocompromised at least four months after they received the first booster dose of any authorized or approved COVID vaccine. Immunocompromised people must be at least 12 to receive the 2nd Pfizer booster, and at least 18 to get the Moderna.

"Current evidence suggests some waning of protection over time against serious outcomes from COVID-19 in older and immunocompromised individuals. Based on an analysis of emerging data, a second booster dose of either the Pfizer-BioNTech or Moderna COVID-19 vaccine could help increase protection levels for these higher-risk individuals," said Peter Marks, M.D., Ph.D., director of the FDA's Center for Biologics Evaluation and Research. "Additionally, the data show that an initial booster dose is critical in helping to protect all adults from the potentially severe outcomes of COVID-19. So, those who have not received their initial booster dose are strongly encouraged to do so."