Univariate analysis revealed significant associations of serum PCT, CRP, and WBC levels with co‐infections with H1N1 and bacteria (odds ratio [OR]: 1.65, 95% confidence interval [CI], 1.34‐2.06, P < 0.001; OR: 1.08, 95% CI, 1.06‐1.09, P < 0.001; OR:1.06, 95% CI, 1.04‐1.09, P = 0.02, respectively). Here, CALCA is linked to coinfection.