The FDA and the CDC authorized third doses of the Pfizer and Moderna COVID vaccines on August 13, 2021 for patients who are moderately to severely immunocompromised. They made this decision after research studies found that a third dose improved the immune response to the vaccine in some immunocompromised patients. This is not considered a "booster," which is a dose of a vaccine given because immunity has decreased over time. Instead, it appears that some people need three vaccine doses instead of two as part of their initial vaccination, in order to have the best possible protection against getting COVID-19.

As of August 13, 2021, the CDC is recommending that moderately to severely immunocompromised people receive an additional dose of the COVID-19 vaccine, including:

  • People who have received chemotherapy or radiation for treatment of cancer within the last year
  • People who have had a solid organ transplant and still take medication for immune suppression
  • People who have had a stem cell transplant in the last two years, or who have had a stem cell transplant >2 years ago but still need medication for immune suppression
  • People who have a history of a primary immunodeficiency, such as Wiskott-Aldrich syndrome, DiGeorge syndrome, or CVID
  • People who have HIV with a CD4 count <200 or are not on antiretroviral medications
  • People who take >=20 mg of prednisone per day, or the equivalent dose of another steroid
  • People who take another immune-suppressing medication for treatment of an autoimmune, rheumatologic, neurologic, or inflammatory disease.
It is also important to remember that some patients who are significantly immunocompromised may not have a good immune response to the COVID vaccine even with a third dose. Therefore, you should also continue to mask in indoor public places, to practice social distancing, to wash or sanitize your hands frequently, and to encourage your close contacts to get vaccinated.