A study published in Pediatrics reports on Apr. 8 that influenza vaccines provided strong protection for children across Europe over two recent flu seasons, especially against influenza B and H1N1 viruses.
The findings are significant because they highlight the consistent benefits of vaccination for children who visit primary care clinics due to influenza. Researchers say this evidence supports ongoing efforts to increase vaccine uptake and monitor effectiveness to guide immunization strategies.
The study analyzed data from more than 19,000 pediatric patients at primary care centers in nine European countries during the 2022–2023 and 2023–2024 seasons. Vaccine effectiveness ranged from 57% to 83% in the first season and increased to between 71% and 92% in the second season, depending on virus subtype. Protection was highest against influenza B and H1N1 but remained lower for H3N2.
Researchers collected clinical samples from children presenting with symptoms of acute respiratory tract infections within eight days of onset. They confirmed influenza infection using real-time PCR testing, allowing them to distinguish between cases (PCR-positive) and controls (PCR-negative). Vaccination status was verified through health records or patient/guardian reports, considering only those vaccinated at least two weeks before symptom onset as protected.
The analysis showed that younger children generally experienced higher vaccine effectiveness compared to older ones, particularly against H1N1 and influenza B. However, protection against H3N2 varied by age group and season. The study also found that removing data from infants under one year old did not significantly change results.
Authors emphasize that improving vaccination coverage among recommended target groups is important for maximizing benefits and reducing seasonal flu burden among children. They also call for continued monitoring of vaccine performance by age group and virus subtype to inform future updates or expansions of immunization programs. The researchers caution that some subgroup findings should be interpreted carefully due to limited data on dose history or small sample sizes.
