"The FDA is closely monitoring data as it becomes available from studies administering an additional dose of the authorized COVID-19 vaccines to immunocompromised individuals," the FDA told Fox News. "The agency, along with the CDC, is evaluating potential options on this issue, and will share information in the near future."
Two sources familiar with the FDA's plans told NBC News that the agency is expected to give the go-ahead for a third dose of the Pfizer and Moderna COVID-19 vaccines, following health officials' warning for immunocompromised people.
Roughly 2.7% of the U.S. adult population is immunocompromised, according to the U.S. Centers for Disease Control and Prevention (CDC). This includes people with cancer, recipients or organ transplants, or persons living with HIV, among others.
A study in the New England Journal of Medicine published Wednesday reported that a third dose of Moderna's COVID-19 vaccine substantially improved protection for organ transplant recipients whose weak immune systems don't always respond to the standard to two shots.
The Associated Press contributed to this report.