Robust SARS-CoV-2 Neutralizing Antibodies Sustained through Three Months Post XBB.1.5 mRNA Vaccine Booster

SARS-CoV-2-neutralizing antibodies were substantially expanded one month after a shot of XBB.1.5 monovalent mRNA vaccine (XBB.1.5 MV) booster, but the durability of this response remained unknown. Here, we addressed this question by performing neutralization assays on four viral variants (D614G, BA.5, XBB.1.5, and JN.1) using sera from 39 adult participants obtained at ~1 month and ~3 months post an XBB.1.5 MV booster. Our findings indicate that the resultant neutralizing antibody titers were robust and generally maintained at stable levels for the study period, similar to those following XBB infection. Importantly, this durability of neutralizing antibody titers contrasts with the decline observed after a booster of the original monovalent or BA.5 bivalent mRNA vaccine. Our results are in line with the recent national data from the Centers for Disease Control and Prevention, showing the efficacy against symptomatic SARS-CoV-2 infection is sustained for up to 4 months after an XBB.1.5 MV booster. ### Competing Interest Statement D.D.H. is a co-founder of TaiMed Biologics and RenBio, consultant to WuXi Biologics and Brii Biosciences, and board director for Vicarious Surgical. Aubree Gordon served on a scientific advisory board for Janssen Pharmaceuticals. Other authors declare no competing interests.