Characterization of immune responses in fully vaccinated individuals after breakthrough infection with the SARS-CoV-2 delta variant
Ai‐ris Y. Collier, Catherine Brown, Katherine McMahan, Jingyou Yu, Jinyan Liu, Catherine Jacob-Dolan, Abishek Chandrashekar, Dylan B. Tierney, Jessica L. Ansel, Marjorie Rowe, Daniel Sellers, Kunza Ahmad, Ricardo Aguayo, Tochi Anioke, Sarah Gardner, Mazuba Siamatu, Lorraine Belisse Bermudez Rivera, Michele R. Hacker, Lawrence C. Madoff, Dan H. Barouch
Abstract
Breakthrough infections with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants have been reported frequently in vaccinated individuals with waning immunity. In particular, a cluster of over 1000 infections with the SARS-CoV-2 delta variant was identified in a predominantly fully vaccinated population in Provincetown, Massachusetts in July 2021. In this study, vaccinated individuals who tested positive for SARS-CoV-2 ( n = 16) demonstrated substantially higher serum antibody responses than vaccinated individuals who tested negative for SARS-CoV-2 ( n = 23), including 32-fold higher binding antibody titers and 31-fold higher neutralizing antibody titers against the SARS-CoV-2 delta variant. Vaccinated individuals who tested positive also showed higher mucosal antibody responses in nasal secretions and higher spike protein–specific CD8 + T cell responses in peripheral blood than did vaccinated individuals who tested negative. These data demonstrate that fully vaccinated individuals developed robust anamnestic antibody and T cell responses after infection with the SARS-CoV-2 delta variant. Moreover, these findings suggest that population immunity will likely increase over time by a combination of widespread vaccination and breakthrough infections.