PSMD1 and COVID-19: The multivariate analysis identified older age (adjusted odds ratio [aOR] 1.07, 95% confidence interval [CI] 1.01–1.12, P = 0.014) and low anti-S1 IgG titer in the early phase (aOR 0.88, 95% CI 0.77–0.99, P = 0.037) as independent risk factors for severe breakthrough COVID-19.