LAUSR

ABSTRACT Background The immune persistence of neutralizing antibodies elicited by BBIBP-CorV vaccines on day 0–14, 0–21 and 0–28 schedule, and the immunogenicity and safety of a homologous booster dose after different priming vaccination regimens is scarcely reported. Methods : Responders (GMT≥16) at day 28, after priming with the two-dose vaccine, were followed up at 3, 6, and 10 months. Eligible participants received a homologous booster dose at month 10 and were followed-up 28 days post-booster. Results The GMT of neutralizing antibodies in 0–28d-10 m and 0–21d-10 m group were significantly higher than 0–14d-10 m group from month 3 (71.6 & 64.2 vs 46.4, p < 0.001) to month 10 (32.4 & 28.8 vs 20.3, p < 0.001) after the second dose. On day 28 post-booster, a remarkable rebound in neutralizing antibodies (246.2, 277.5, and 288.6, respectively) was observed in the three groups. All adverse reactions were mild after booster injection. Conclusions The priming two-dose BBIBP-CorV vaccine with 0–28 days and 0–21 days schedule could lead to a longer persistence of neutralizing antibody than the 0–14 days schedule. Regardless of the priming vaccination regimens, a homologous booster dose led to a strong rebound in neutralizing antibodies and might persist for at least 18 months.