Mary Altaffer, Associated Press file
In this Jan. 15, 2021, file photo, Dr. Yomaris Pena, Internal Medicine Physician with Somos Community Care at a COVID-19 extracts the Pfizer COVID-19 Vaccine out of a vial at a vaccination site at the Corsi Houses in the East Harlem neighborhood of New York. U.S. health regulators have authorized extra doses of the COVID-19 vaccines in people with weakened immune systems to better protect them from the virus. The announcement Thursday, Aug. 12. by the Food and Drug Administration applies to millions of Americans who take immune-suppressing medicines because of organ transplants, cancer or other disorders.