Clinical Outcomes and Complications of Influenza A and B in Hospitalized Children

Background: Influenza remains a major cause of hospitalization and severe complications in children worldwide, particularly in young children and those with underlying health conditions. Objectives: This study compared pulmonary and extrapulmonary complications, therapeutic interventions, and outcomes in pediatric patients with influenza A and B admitted to Mardani Azari Pediatric Educational and Therapeutic Center, Tabriz, Iran, during 2022–2023. Methods: A retrospective observational study was conducted among 226 hospitalized children aged up to 15 years with PCR-confirmed influenza. Demographic, clinical, and laboratory data were collected and analyzed using parametric and nonparametric statistical tests. Results: Among the 226 patients, 169 (74.8%) had influenza A, predominantly H3N2 subtype, and 57 (25.2%) had influenza B. The mean age was 4.51±7.64 years with no significant age or sex differences between groups. Pneumonia was the most common pulmonary complication and was significantly more frequent in influenza A patients, particularly among H3N2 cases. Air trapping occurred more frequently in influenza B patients. Extrapulmonary complications were rare, with sinusitis and otitis being the most common; otitis was significantly more prevalent in influenza B cases. No significant differences were found between groups regarding length of hospital stay, inflammatory markers, or mortality rates, although influenza A was associated with a slightly higher mortality rate (9.5% vs. 7.0%). Conclusions: While both influenza A and B infections caused notable morbidity, influenza A, especially H3N2, was associated with more severe pulmonary complications. These findings highlight the importance of early recognition, appropriate management, and routine vaccination to reduce influenza-related morbidity and mortality in pediatric populations.