ALB and lymphopenia: The independent risk factors associated with progression to severe disease in the delta-confirmed subgroup were BMI ≥ 25 kg/m2 (HR 1.987, 95% CI 1.068–3.697), SpO2 < 97% (HR 4.309, 95% CI 2.411–7.701), lymphopenia < 1500/μL (HR 5.119, 95% CI 1.233–21.259), albumin < 4.0 g/dL (HR 3.382, 95% CI 1.790–6.389), and CRP elevation > 1.5 mg/dL (HR 4.169, 95% CI 1.841–9.442).