Neutralization of five SARS-CoV-2 variants of concern by convalescent and BBIBP-CorV vaccinee serum.

The prevalence of SARS-CoV-2 variants of concern (VOCs) is still escalating throughout the world. However, the level of neutralization of the inactivated viral vaccine recipients' sera and convalescent sera against all VOCs, including B.1.1.7 (Alpha), B.1.351 (Beta), P.1 (Gamma), B.1.617.2 (Delta), and B.1.1.529 (Omicron) remains to be lack of comparative analysis. Therefore, we constructed pseudoviruses of five VOCs using a lentiviral-based system and analyzed their viral infectivity and neutralization resistance to convalescent and BBIBP-CorV vaccinee serum at different times. Our results show that, compared with the wild-type strain (WT), five VOC pseudoviruses showed higher infection, of which B.1.617.2 and B.1.1.529 variant pseudoviruses exhibited higher infection rates than wild-type or other VOC strains, respectively. Sera from 10 vaccinated individuals at the 1, 3 and 5-month post second dose or from 10 convalescent at 14 and 200 days after discharge retained neutralizing activity against all strains but exhibited decreased neutralization activity significantly against the five VOC variant pseudoviruses over time compared to WT. Notably, 100% (30/30) of the vaccinee serum samples showed more than a 2.5-fold reduction in neutralizing activity against B.1.1.529, and 90% (18/20) of the convalescent serum samples showed more than 2.5-fold reduction in neutralization against B.1.1.529. These findings demonstrate the reduced protection against the VOCs in vaccinated and convalescent individuals over time, indicating that it is necessary to have a booster shot and develop new vaccines capable of eliciting broad neutralization antibodies.

The neutralization of B.1.617.1 and B.1.1.529 sera from convalescent patients and BBIBP-CorV vaccines.

The SARS-CoV-2 variants B.1.617.1 (Kappa) contain multiple mutations in the spike protein. However, the effect of B.1.617.1 lineage-related mutants on viral infectivity and inactivated-virus vaccine efficacy remains to be defined. We therefore constructed 12 B.1.617.1-related pseudoviruses and systematically studied the effects of mutations on virus infectivity and neutralization resistance to convalescent and inactivated virus vaccine sera. Our results show that the B.1.617.1 variant exhibited both higher infectivity and neutralization resistance in sera at 1 or 3 months after vaccination of 28 individuals and at 14 and 200 days after discharge of 15 convalescents. Notably, 89% of vaccines and 100% of the convalescent serum samples showed more than 2.5-fold reduction in neutralization against one single mutation: E484Q. Besides, we found a significant decrease in neutralizing activity in convalescent patients and BBIBP-CorV vaccines for B.1.1.529. These findings demonstrate that inactivated-virus vaccination or convalescent sera showed reduced, but still significant, neutralization against the B.1.617.1 variant.