2.4 Statistical analysis
Continuous variables are described medians (interquartile ranges, IQRs). Categorical variables are presented as frequencies and percentages. Comparisons of proportions were performed with chi-square and Fisher’s exact tests; continuous variables were compared using the Mann–Whitney U test. All probabilities were 2-tailed, with statistical significance defined as P ≤ .05. Binary logistic regression was performed to estimate the odds ratio (OR) and 95% confidence interval (CI) for comparison of clinical hospitalization outcomes in H1N1-infected, SAR-COV-2 infected and mixed infected groups. Adjustment factors included age, sex, comorbidities and smoking history. These risk factors were previously shown to be associated with the clinical prognosis of influenza and COVID-19 patients and served as confounders24,25. All analyses were performed using STATA, version 14.