Fig. 3. Induction of humoral responses by prime-boost vaccination.

a Homologous prime-boost of IFNAR^−/− mice (n = 6 or n = 4 for the empty MV control) immunized intraperitoneally with 1 × 10⁵ TCID₅₀ of the indicated rMV at days 0 and 28. Sera were collected 28 and 42 days after immunization and assessed for specific antibody responses to b MV antigens or c S-SARS-CoV-2 S. The data show the reciprocal endpoint dilution titers with each data point representing an individual animal. d Neutralizing antibody responses to SARS-CoV-2 virus expressed as 50% plaque reduction neutralization test (PRNT₅₀) titers. e IgG subclass of S-specific antibody responses in mice 4 weeks after the first immunization. f Ratio of IgG2a/IgG1 responses. Data are represented as geometric mean with line and error bars indicating ±geometric SD. Statistical significance was determined by two-way ANOVA with Tukey’s multiple comparisons test.