Immunogenicity against prototype SARS-CoV-2 virus and omicron BA.1.1 variant
VIRUS
The immunogenicity of NVSI-06-09 as a booster dose was evaluated and compared with BBIBP-CorV by using a live-virus microneutralization assay. Before booster vaccination, neutralizing antibodies (nAbs) against the prototype SARS-CoV-2 virus were detectable (nAb titer ≥4) in most participants in NVSI-06-09 (99.61%) and BBIBP-CorV (99.20%) groups, with nAb geometric mean titers (GMTs) of 119.42 (95%CI, 106.47–133.95) and 113.29 (100.50–127.71), respectively (Fig. The live-virus neutralizing antibody titers, along with the corresponding fourfold rise rate, against prototype SARS-CoV-2 strain and Omicron BA.1.1 variant induced by the booster vaccination of NVSI-06-09, compared with those boosted with BBIBP-CorV. At pre-booster baseline, 96.86% participants in NVSI-06-09 group and 97.19% in BBIBP-CorV group exhibited detectable nAbs against the Omicron BA.1.1 variant, with the GMT values of 40.47 (95% CI, 34.86–46.97) and 37.91 (32.64–44.04), respectively (Fig. As demonstrated by the results presented above, the BBIBP-CorV booster elicited similar or lower nAb GMT fold rise against Omicron BA.1.1 variant than that against prototype strain (3.78-fold vs 4.47-fold). By contrary, the NVSI-06-09 booster induced a much greater GMT fold rise against Omicron BA.1.1 strain than that against prototype virus (42.35-fold vs 19.67-fold). These results indicated that the NVSI-06-09 booster exhibited remarkably better immunogenicity against SARS-CoV-2 virus, especially Omicron BA.1.1 variant.Then, we further investigated whether the gender and age of participants have influences on the immune response of booster vaccinations. Statistical analyses were performed after stratifying participants into male and female subgroups, as well as into different age subgroups. The analysis results showed that the nAb responses against prototype virus and Omicron BA.1.1 variant boosted by either NVSI-06-09 or BBIBP-CorV were gender-independent and also age-independent. The post-booster nAb GMTs were comparable between male and female participants (all 