Mounting evidence for immunizing previously infected subjects with a single dose of SARS-CoV-2 vaccine.

Efforts to best protect the world from SARS-CoV-2 as variants emerge and despite limited vaccine supply are ongoing. One strategy that may maximize vaccine coverage and expedite immunization campaigns involves providing single mRNA vaccine doses to individuals with previous COVID-19. In this issue of the JCI, two independent studies, one by Levi and Azzolini et al. and another by Mazzoni and Di Lauria et al., explored vaccine responses in individuals previously infected with the virus. Levi and Azzolini and colleagues used multilinear regression models to correlate exposure and symptoms with antibody response to the vaccine. Mazzoni and Di Lauria and colleagues characterized B cell and T cell kinetics in whole blood after one and two doses of vaccine in health care workers with and without previous infection. Both studies indicated that one vaccine dose may sufficiently protect individuals who have recovered from COVID-19. Implementing a single-dose mRNA vaccine protocol in previously symptomatic individuals may facilitate and expedite immunization campaigns.