Robust immune responses are observed after one dose of BNT162b2 mRNA vaccine dose in SARS-CoV-2–experienced individuals.

The use of coronavirus disease 2019 (COVID-19) vaccines will play the major role in helping to end the pandemic that has killed millions worldwide. COVID-19 vaccines have resulted in robust humoral responses and protective efficacy in human trials, but efficacy trials excluded individuals with a prior diagnosis of COVID-19. As a result, little is known about how immune responses induced by mRNA vaccines differ in individuals who recovered from COVID-19. Here, we evaluated longitudinal immune responses to two-dose BNT162b2 mRNA vaccination in 15 adults who had experienced COVID-19, compared to 21 adults who did not have prior COVID-19. Consistent with prior studies of mRNA vaccines, we observed robust cytotoxic CD8⁺ T cell responses in both cohorts after the second dose. Furthermore, SARS-CoV-2–naive individuals had progressive increases in humoral and antigen-specific antibody-secreting cell (ASC) responses after each dose of vaccine, whereas SARS-CoV-2–experienced individuals demonstrated strong humoral and antigen-specific ASC responses to the first dose but these responses were not further enhanced after the second dose of the vaccine at the time points studied. Together, these data highlight the relevance of immunological history for understanding vaccine immune responses and may have implications for personalizing mRNA vaccination regimens used to prevent COVID-19, including for the deployment of booster shots. The impact of prior immunity: Prior infection with SARS-CoV-2 elicits antibodies and T cell responses that influence subsequent responses to vaccines. Here, Samanovic et al. evaluated adaptive immune responses in individuals who received two doses of the BNT162b2 COVID-19 vaccine with or without prior confirmed SARS-CoV-2 infection. The authors found that humoral and cellular immune responses were elicited in both cohorts. Individuals who were vaccinated after prior infection exhibited increased humoral immunity after the first dose of vaccine that was stable after the second dose. Together, these findings show that immunological history may be important for vaccine and booster regimens. [ABSTRACT FROM AUTHOR]