IL6 and coinfection: Based on the value of lambda.1se, 16 variables with non-zero coefficients were selected as candidate predictors, including age, low birthweight, preterm birth, personal history of atopy, underlying condition, wheezing, seizures, poor appetite, leucocyte count, NLR, ESR, CRP, IL-6, LDH, D-dimer, and co-infection (Figures 2A–C).