SERPINA1 and COVID-19: Factors associated with a higher likelihood of severe COVID-19 were being male, older, smoking, age-associated comorbidities, and having an A1AT level below 116 mg/dL [OR 1.398, p = 0.003], and a variant of the SERPINA1 gene that could affect A1AT protein [OR 1.294, p = 0.022].