Effects of sex on antibody responses to irradiated sporozoite vaccination. Adult (8–10 weeks) male and female mice were twice vaccinated with irradiated sporozoites at 14-day intervals. Forty-two days post boost vaccination, plasma was collected and anti-CSP IgG titers (A), areas under the curve (AUC) (B), anti-CSP titers equal to an optical density-1 (C), anti-CSP antibody concentrations (D), anti-CSP antibody avidity (E), anti-CSP IgG1 titers (F), anti-CSP IgG2a titers (G), and the ratio of IgG1/IgG2a (H) were measured. Data represent means ± the SEM from two independent replications (n = 34–39/sex) and significant differences are denoted with asterisks (**P < 0.01, *** < 0.001, ****P < 0.0001).