The third COVID-19 vaccine dose Ruth J. García-Reyes, Pharm.D, PGY-1 | Pharmacy Resident at VA Caribbean Healthcare System
There is a difference between the third dose of COVID-19 vaccine versus booster shot. The third dose of the vaccine is currently considered part of the primary series in immunocompromised patients and is intended to build an immune response like most people get with two doses.
On August 2021, the United States Food and Drug Administration (FDA) authorized a third dose of the PfizerBioNTech and Moderna mRNA vaccines for patients that have moderate to severe immunocompromising conditions. This authorization is based upon studies showing that the immune response in this patient population is suboptimal and with the administration of a third dose, immune response may improve. The third dose should be given 28 days after the second dose for such individuals and must be the same brand vaccine received previously.1
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Studies of transplant recipients who received a third dose of mRNA vaccines, seroconversion rates were higher after the additional dose, although approximately 50 to 70% who were seronegative after two doses remained seronegative.2 Patients that are eligible for a third dose include: active use of chemotherapy for cancer, hematologic malignancies, hematopoietic stem cell or solid organ transplant, advanced or untreated HIV infection with CD4 cell count <200 cells/ microL, moderate or severe primary immunodeficiency disorder, and use of immunosuppressive medications (eg,
