Low neutralization of SARS-CoV-2 Omicron BA.5.2.48 and XBB.1 sub-variants in response to breakthrough infection by booster.

• Serum from breakthrough infections can induce broad neutralization. • Vaccines play a role by reducing viral load and attenuating infection symptoms. • Omicron XBB.1.16 exhibits a high potential for immune escape. To assess the levels of and neutralizing antibodies against severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) and its mutants in serum samples from patients with breakthrough infection. Sixty-four patients with breakthrough infections were recruited for this cross-sectional study. All samples were used to neutralizing antibodies (nAbs) against SARS-CoV-2 and its mutants using a focused reduction neutralization assay. A total of 512 serum samples were obtained from unvaccinated patients who received one dose of vaccine (n = 12), received two doses of vaccine (n = 15), and received three doses of vaccine (n = 37). The geometric mean titer (GMT) of neutralizing antibodies against the Omicron subvariant was significantly lower (GMT 66.8 and 56.1) compared to the original strain, regardless of whether two or three doses of vaccine were administered. This result highlights that sera from breakthrough infections induce broad neutralization, but Omicron XBB.1.16 exhibits high immune evasion potential. [ABSTRACT FROM AUTHOR]