Three doses of COVID-19 mRNA vaccination safe in high-risk populations

Earlier reports have suggested the high effectiveness of messenger ribonucleic acid (mRNA) coronavirus disease (COVID-19) vaccines at preventing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. However, their efficacy against mild COVID-19 disease appears to wane over time. Thus, the need for additional/booster vaccine doses is being contemplated. This retrospective study included adults within the Mayo Clinic Enterprise who were vaccinated with three doses of United States Food and Drug Administration (FDA)-approved mRNA-based COVID-19 vaccines from December 1, 2020, to October 17, 2021. Participants received the first two doses of BNT162b2 or mRNA-1273 according to the emergency use authorization (EUA) protocol. The study participants were administered a third dose of the same vaccine type as the original two doses at least 28 days after the second dose. All subjects were followed up for at least 14 days after their third vaccine dose.