PSMD1 and COVID-19: SARS-CoV-2 anti-S1 IgG, neutralizing antibody activity, and reactivity against all four different fragments of the SARS-CoV-2 spike protein significantly increased from before second vaccination to after second vaccination (for all P < 0.001) and from after COVID-19 in unvaccinated patients to after single-dose vaccination in patients with prior infection, respectively (for all P < 0.05; Figures 5A–F).