Omicron BA.4/5 Neutralization and T-Cell Responses in Organ Transplant Recipients after Booster Messenger RNA Vaccine: A Multicenter Cohort Study

Abstract

Background: In solid organ transplant (SOT) recipients, the primary vaccination series against Coronavirus Disease 2019 is 3 doses followed by boosters. We determined whether a fourth dose booster induced Omicron BA.4/5 neutralizing antibodies (nAbs) and T cells in a large multicenter cohort study. Methods: Serum was collected 4-6 weeks post-third and post-fourth doses of messenger RNA vaccine in 222 SOT recipients. nAbs were measured using a pseudovirus neutralization assay that targeted the Omicron BA.4/5 spike protein. A subset underwent T-cell testing. Results: The median age of the cohort was 63 years (interquartile range [IQR], 50-68) with 61.7% men. BA.4/5 nAb detection increased from 26.6% (59 of 222) post-third dose to 53.6% (119 of 222) post-fourth dose (P