Third Dose Approved for Those with Weaker Immune Systems

August 17, 2021

The U.S. Food and Drug Administration and the CDC have approved booster shots of COVID-19 vaccines for moderately to severely immunocompromised individuals.

Given the viciousness of Delta—the latest and fastest-spreading COVID-19 variant—the agencies favor third shots of Pfizer-BioNTech and Moderna vaccines for those whose immune response is less able to battle the coronavirus.

That group includes people who have:

• Been receiving active cancer treatment for tumors or cancers of the blood
• Received an organ transplant and are taking medicine to suppress the immune system
• Received a stem cell transplant within the last 2 years or are taking medicine to suppress the immune system
• Moderate or severe primary immunodeficiency (such as DiGeorge syndrome, Wiskott-Aldrich syndrome)
• Advanced or untreated HIV infection
• Active treatment with high-dose corticosteroids or other drugs that may suppress your immune response

Pfizer and Moderna boosters are expected to eventually expand to others. The latest Pfizer and Moderna research suggests diminishing protection after six months.

In a study Pfizer posted online in late July, they reported the vaccine’s efficacy against COVID-19 symptomatic disease dropped from 96% to 84% four to six months after the second shot. However, the same study reported the vaccine’s overall efficacy against severe COVID-19 disease was still 97%, demonstrating that the vaccine remains a strong defense against severe disease and hospitalization.

Houston and Harris County officials and a vast majority of medical experts encourage continued use of masks, social distancing and frequent handwashing. If you have any questions about whether you or a loved one should get a third shot of Pfizer or Moderna, talk with your health care provider and learn more here.

The information in this article is accurate as of August 17, 2021. It was clinically reviewed by Binita Patel.