The impact of influenza vaccination on the clinical severity of influenza among children aged 6 months to 6 years living in the community: a prospective cohort study.

PURPOSE: Evidence on whether influenza vaccination reduces disease severity in children with breakthrough infections in community settings is limited. MATERIALS AND METHODS: This prospective study enrolled 388 children (aged 6 months-6 years) diagnosed with influenza at a community health center in Shenzhen from May 2024 to October 2025. Participants were grouped by vaccination status within the prior year: vaccinated (n=196) and unvaccinated (n=192). Clinical characteristics, healthcare utilization, and outcomes were compared. RESULTS: Vaccinated children showed significantly lower peak body temperature (38.81°C±0.58°C vs. 39.03°C±0.64°C), shorter fever duration (2.01±1.21 days vs. 2.45±1.55 days), and fewer symptoms like myalgia and gastrointestinal issues (all p<0.01). They also had fewer outpatient visits, lower outpatient costs, and markedly reduced rates of hospitalization (4.1% vs. 21.9%) and antibiotic use (5.6% vs. 15.1%) (all p<0.05). CONCLUSION: Influenza vaccination could mitigate symptoms, reduce hospitalization and antibiotic use, and lessen the healthcare burden from breakthrough infections.