PROS1 and COVID-19: Among 9117 patients with clinical or central laboratory-confirmed RSV, SARS-CoV-2, or influenza infection, 1119 were excluded from this analysis primarily due to confirmed coinfection (200 patients) (eTable 2 in Supplement 1), possible coinfection (376 patients), patients with COVID-19 with only 1 mRNA or 1 recombinant S protein vaccine dose (230 patients), unknown COVID-19 or influenza vaccination history (198 patients), or unknown clinical outcomes (70 patients) (eFigure 2 in Supplement 1).