Association between high levels of vaccine-induced antibodies and lower odds of Omicron breakthrough infection were more pronounced in females than to males
(A) Comparison of spike-specific IgG levels (AU/mL) quantified at a study visit prior to a positive (case) or negative (control) PCR test stratified by sex showing the geometric mean and 95% CI (n = 285 females and n = 197 males). SARS-CoV-2 variants from left to right: Wildtype (Wuhan-Hu-1), Omicron BA.1, and Omicron BA.2. ∗∗∗ = p < 0.001.
(B) Multivariable logistic regression showing the adjusted odds ratios (aORs) and 95% CI for breakthrough infection for ACE2-blocking antibody titers in tertiles (wildtype) or quintiles (Omicron variants) stratified by sex. The analysis adjusts for the matched variables: age group, sex, vaccine, and study visit, and for the unmatched variables: vaccine priority group, Charlson comorbidity index (CCI), visit year, days from study visit to PCR test, and days from third vaccination to PCR test.