Three doses of an inactivation-based COVID-19 vaccine induces cross-neutralizing immunity against the SARS CoV-2 Omicron variant

Figures & data

Figure 1. Neutralizing antibody production following booster vaccination. (A, B) Neutralization titres against the prototype, Delta, and Omicron SARS Cov-2 variants in individuals after the third vaccination within 2 months. The limitation of detection (LOD) was 1:10. Titres below the LOD were set to 0.5 times the LOD. Numbers in black above each virus strain are geometric mean titers (GMT) of the neutralization titers (ND50) resulting in serum pseudovirus neutralization test. Numbers in red denote fold-change in GMT between different pseudovirus. (C) Comparison of neutralization titres against the prototype, Delta, and Omicron SARS Cov-2 variants in individuals after the third vaccination within 2 months (n = 200, P-values were obtained by the unpaired t-test, ***P < 0.0001). (D) Neutralization activity of sera from individuals at various time points after booster immunization against different SARS Cov-2 variants. Prototype, 1 month vs 2 months: P = 0.4698, Delta variant, 1 month vs 2 months: P = 0.97, Omicron variant, 1 month vs 2 months: P = 0.46; ns, not significant.

Table 1. Neutralization-positive rates against the pseudotyped SARSCov-2 variant.

	Prototype	Delta	Omicron
Positive rate	99.50%	98.50%	95.50%
Negative rate	0.50%	1.50%	4.50%

Note: Titres up 1:10 were considered to be positive.