Booster dose of BNT162b2 in a CoronaVac primary vaccination protocol improves neutralization of SARS-CoV-2 Omicron variant

Abstract

The emergence of the new SARS-CoV-2 Omicron variant, which is known to accumulate a huge number of mutations when compared to other variants, brought to light the concern about vaccine escape, especially from the neutralization by antibodies induced by vaccination. In this scenario, we evaluated the impact on antibody neutralization induction, against Omicron variant, by a booster dose of BNT162b2 mRNA vaccine after the CoronaVac primary vaccination scheme. The percentage of seroconverted individuals 30 and 60 days after CoronaVac scheme was 17% and 10%, respectively. After booster dose administration, the seroconvertion rate increased to 76.6%. The neutralization mean titer against Omicron in the CoronaVac protocol decreased over time, but after the booster dose, the mean titer increased 43.1 times, indicating a positive impact of this vaccine combination in the serological immune response.

Figure 1.

Viral microneutralization assay against SARS-CoV-2 omicron variant: 30 days after CoronaVac second dose (D30); 60 days after CoronaVac second dose (D60); 270 days after CoronaVac second dose and 30 days after BNT162b2 booster (D270). The dark grey circles represent the included participants, and the 50% neutralizing titer (VNT₅₀) for each sample was assayed using the Omicron variant live virus (HIAE – W.A) (See the Supplementary Appendix for methods description). The blue bars represent the VNT₅₀ mean values. The dashed line represents the lower limit of detection (LOD), determined in this assay as 20. The percentage of seroconverted samples, for each group, is indicated in the graph. The statistical analysis was obtained by one-way ANOVA and Tukey’s multiple comparisons test, where the three asterisks represent the P value < 0.0001.