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Published on: January 30, 2017
Vaccine Effectiveness Against Pediatric Influenza-A-Associated Urgent Care, Emergency Department, and Hospital
Katherine Adams1, Zachary A Weber2, Duck-Hye Yang2
1Influenza Division, Centers for Disease Control and Prevention, Atlanta, Georgia, USA.
Insights
Influenza vaccination significantly reduced pediatric hospitalizations during the 2022-2023 season, with vaccine effectiveness (VE) at 48% for emergency visits and 40% for hospitalizations. This highlights the importance of flu shots for children and adolescents.
Area of Science:
- Pediatric Infectious Diseases
- Vaccinology
- Public Health Surveillance
Background:
- The 2022-2023 influenza season saw the highest pediatric hospitalization rates since 2010-2011 in the US.
- Influenza A/H3N2 was the predominant circulating strain during this period.
Purpose of the Study:
- To estimate the influenza A vaccine effectiveness (VE) in preventing medically attended influenza infections among children and adolescents.
- To analyze VE across different age groups and healthcare encounter types (emergency department/urgent care vs. hospitalization).
Main Methods:
- A test-negative case-control study was conducted using data from three health systems.
- Participants included children and adolescents (6 months-17 years) with molecular influenza testing from October 2022 to March 2023.
- Vaccine effectiveness was calculated by comparing vaccination status between influenza-positive cases and influenza-negative controls, adjusting for confounders using inverse-propensity-to-be-vaccinated weights.
Main Results:
- Overall VE against influenza A was 48% for emergency department/urgent care encounters and 40% for hospitalizations.
- VE was higher in younger children (6 months-4 years): 53% for ED/UC and 56% for hospitalizations.
- VE was lower in older children and adolescents (9-17 years): 38% for ED/UC and 46% for hospitalizations.
Conclusions:
- Influenza vaccination substantially reduced the risk of emergency department/urgent care encounters and hospitalizations by approximately 40-48% during the 2022-2023 season.
- Influenza vaccination is a crucial intervention for preventing moderate to severe influenza illness in pediatric populations.
- Findings underscore the continued importance of seasonal influenza vaccination for children and adolescents to mitigate severe outcomes.
Background:
During the 2022-2023 influenza season, the United States experienced the highest influenza-associated pediatric hospitalization rate since 2010-2011. Influenza A/H3N2 infections were predominant.
Methods:
We analyzed acute respiratory illness (ARI)-associated emergency department or urgent care (ED/UC) encounters or hospitalizations at 3 health systems among children and adolescents aged 6 months-17 years who had influenza molecular testing during October 2022-March 2023. We estimated influenza A vaccine effectiveness (VE) using a test-negative approach. The odds of vaccination among influenza-A-positive cases and influenza-negative controls were compared after adjusting for confounders and applying inverse-propensity-to-be-vaccinated weights. We developed overall and age-stratified VE models.
Results:
Overall, 13 547 of 44 787 (30.2%) eligible ED/UC encounters and 263 of 1862 (14.1%) hospitalizations were influenza-A-positive cases. Among ED/UC patients, 15.2% of influenza-positive versus 27.1% of influenza-negative patients were vaccinated; VE was 48% (95% confidence interval [CI], 44-52%) overall, 53% (95% CI, 47-58%) among children aged 6 months-4 years, and 38% (95% CI, 30-45%) among those aged 9-17 years. Among hospitalizations, 17.5% of influenza-positive versus 33.4% of influenza-negative patients were vaccinated; VE was 40% (95% CI, 6-61%) overall, 56% (95% CI, 23-75%) among children ages 6 months-4 years, and 46% (95% CI, 2-70%) among those 5-17 years.
Conclusions:
During the 2022-2023 influenza season, vaccination reduced the risk of influenza-associated ED/UC encounters and hospitalizations by almost half (overall VE, 40-48%). Influenza vaccination is a critical tool to prevent moderate-to-severe influenza illness in children and adolescents.
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