Clinical characteristics and predictors of severe pertussis in hospitalized children after the COVID-19 period in Türkiye: a multicenter study.

Pertussis resurged globally, after the relaxation of COVID-19 measures, underscoring its continued relevance as a public health concern, yet data remain limited on the factors associated with severe disease in children. The present study identified risk factors for severe pertussis to improve early recognition and clinical management. This multicenter retrospective study analyzed the demographic, clinical, and laboratory data of the 839 children hospitalized with laboratory-confirmed pertussis across 47 centers in Türkiye (2023-2024). Severe disease was defined as the need for respiratory support or the development of encephalopathy and/or cardiovascular dysfunction. After univariate comparison, significant variables were evaluated using center-adjusted multivariable logistic regression in vaccine-eligible (> 2 months) and non-eligible (≤ 2 months) groups. The patient's median age was 2 months (IQR 1.5-5.0), and 77.8% were younger than 6 months. Severe disease occurred in 26.1% of cases. In univariate analysis, younger age, vaccine refusal, refugee status, feeding difficulties, apnea, respiratory distress, leukocytosis, viral co-infection, and abnormal chest X-ray findings at admission were associated with severe disease. In infants ≤ 2 months, apnea (OR = 3.74; p < 0.001), respiratory distress (OR = 5.48; p < 0.001), and WBC count (OR = 1.035 per 1 × 10