ALB and susceptibility to pneumonia measurement: The independent risk factors associated with progression to severe disease were age > 70 years (HR 1.574, 95% CI 1.039–2.383), male gender (HR 1.480, 95% CI 1.027–2.135), BMI ≥ 25 kg/m2 (HR 1.830, 95% CI 1.283–2.610), SpO2 < 97% (HR 3.104, 95% CI 2.189–4.402), pneumonia (HR 1.696, 95% CI 1.043–2.759), lymphopenia < 1500/μL (HR 2.182, 95% CI 1.291–3.687), thrombocytopenia (HR 1.501, 95% CI 1.051–2.142), albumin < 4.0 g/dL (HR 2.134, 95% CI 1.407–3.236), and CRP elevation > 5 mg/dL (HR 2.860, 95% CI 1.956–4.182).