Low Neutralization of SARS-CoV-2 Omicron BA5248, XBB15 and JN1 by Homologous Booster and Breakthrough Infection.

Immunity against Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) can be induced through either infection with the virus or vaccination, providing protection against reinfection or reducing the risk of severe clinical outcomes. In this study, we recruited 172 volunteers who received different vaccination regimens, including 124 individuals who had recovered from breakthrough infections caused by the Omicron variant (27 with 2 doses, 49 with 3 doses, and 48 with 4 doses) and 48 healthy donors who did not experience breakthrough infections (all of whom received a fourth dose during the infection wave). We measured neutralizing antibody levels against Omicron BA.5.2.48, XBB.1.5, and JN.1 and found no significant differences in neutralizing antibody titers between natural infection and homologous booster vaccination at 6 months (p > 0.05), with geometric mean titers declining by over 100-fold for some variants relative to the prototype strain.