SARS-CoV-2–specific antibody and T-cell immunity in convalescents after infection wave in Beijing in late 2022

Objectives To evaluate SARS-CoV-2–specific antibody and T-cell responses in convalescents 5 months after infection wave in Beijing from December 2022 to January 2023 to prevent reinfection and severe disease. Methods Convalescents and uninfected individuals vaccinated with different doses were enrolled to assess the IFNγ T-cell responses against SARS-CoV-2 prototype strain, BF.7, BQ.1 and XBB. Neutralizing antibodies against prototype strain, BF.7, BA.5 and XBB and immunoglobulin G antibody were further analyzed. Results In convalescents, the IFNγ T-cell response was significantly higher than that of uninfected individuals (all P <0.001), and the T-cell response against XBB had no significant difference from that of SARS-CoV-2 prototype strain and BF.7 and BQ.1 (all P>0.05). The seropositive rates of IgG antibodies were 100% (303/303) with a median concentration of 90.52 (95% CI, 82.52–99.37). The neutralizing antibodies titers of convalescents against BF.7 and BA.5 were higher than that against the prototype strain (both P < 0.001), while XBB.1.5 was lower (P < 0.001). T-cell response, IgG and neutralizing antibodies had no significant difference in convalescents vaccinated with different doses (all P > 0.05). Conclusions The immunities may have some protective effect against possible future outbreaks and severe diseases of COVID-19.