Peer-reviewed article
Influenza Vaccine Effectiveness Among Children With and Without Underlying Conditions.
Haya Hayek, Emma K Noble, Laura S Stewart, Leila C Sahni, Julie A Boom et al. ·
Summary
Written by AI, not yet AICS's view · claude-haiku-4-5-20251001This study measured how well influenza vaccine protects children with and without underlying health conditions in the United States. Researchers tested over 15,000 children aged 6 months to 17 years who visited emergency departments or were hospitalized during five flu seasons. Vaccination provided protection for both groups, but was less effective in children with underlying conditions, particularly those with respiratory problems.
Key points
- Overall vaccine effectiveness was 43% for children with underlying conditions versus 53% for those without
- Vaccine effectiveness was lowest among children with respiratory conditions at 31%
- Of 15,875 children enrolled, 2,821 (18%) tested positive for influenza
- Vaccination status was verified using state immunization registries or clinical records
- The study covered five influenza seasons from 2015-2020
Limitations
The study only included children who sought emergency care or were hospitalized, so results may not apply to children with milder illness who did not seek care. The analysis was observational and could not establish causation with the same certainty as a randomized trial.
Abstract
OBJECTIVE: Children with certain underlying conditions are at higher risk for severe influenza-related complications. In the United States, annual influenza vaccination is recommended for all children aged 6 months and older, yet vaccine effectiveness (VE) in children with underlying conditions remains less understood. We assessed VE against laboratory-confirmed influenza in children with and without underlying conditions presenting to emergency departments or admitted to hospitals. METHODS: We enrolled US children aged 6 months to 17 years at 7 pediatric medical centers within the New Vaccine Surveillance Network during 5 influenza seasons (2015-2020). Influenza status was confirmed by molecular testing and vaccination status was verified using state immunization registries or from health care clinicians. Underlying conditions were abstracted from medical records or self-reported by parents/guardians. VE was estimated by comparing the odds of vaccination among influenza-positive cases vs controls, adjusting for age, site, and calendar time. RESULTS: Of the 15 875 children included, 2821 (18%) tested positive for influenza. Overall, VE against influenza-associated emergency department visits or hospitalizations was 43% (95% CI: 35%-50%) for children with underlying conditions and 53% (95% CI: 47%-59%) for those without, and there was significant effect measure modification by the presence of underlying conditions (P = .04). VE was lowest among children with respiratory conditions (31%, 95% CI: 19%-42%). CONCLUSION: Influenza vaccination provided protection in both children with and children without underlying conditions. Efforts to improve influenza vaccination coverage and to initiate early treatment for influenza, particularly in populations at increased risk for severe influenza, are essential to reducing influenza-associated complications.