A longitudinal study of humoral immune responses induced by a 3-dose inactivated COVID-19 vaccine in an observational, prospective cohort

• DOI: 10.1186/s12865-022-00532-1
• Publication Date: 2022-11-16T05:02:37Z
• Authors: Yue Tao; Mengyin Ma; Fenghua Hu; Ming Li; Yu Geng; Yawen Wan; Minxin Mao; Lin Chen; Ya Shen; Liguo Zhu; Han Shen; Yuxin Chen
• Keywords: Surrogate endpoint

Abstract Background To determine the dynamic SARS-CoV-2 specific antibody levels induced by 3 doses of an inactivated COVID-19 vaccine, CoronaVac. An observational, prospective cohort study was performed with 93 healthy healthcare workers from a tertiary hospital in Nanjing, China. Serum IgM, IgG, and neutralizing antibodies (NAb) were measured at different time points among participants who received vaccine. Results 91.3% (85/93) 100% (72/72) showed positive both for IgG NAb after 2-dose CoronaVac 3-dose CoronaVac, respectively. Anti-SARS-CoV-2 responses reached 91.21 (55.66–152.06) AU/mL, surrogate 47.60 (25.96–100.81) IU/mL on day 14 second dose. 218.29 (167.53–292.16) AU/mL 445.54 (171.54–810.90) third Additionally, titers highly correlated serum neutralization activities against Ancestral, Omicron, Delta strains. Moreover, significantly higher responses, but not found individuals breakthrough infection when compared to that recipients. Conclusions elicited robust humoral responses. Surrogate assay might substitute pseudovirus assay. Monitoring vaccination would provide important guidance optimization vaccines.