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Influenza Vaccine Effectiveness Among Children for the 2017-2018 Season
Lauren N Powell1, Rodolfo E Bégué2
1Department of Pediatrics, Louisiana State University Health Sciences Center.
Insights
The 2017-2018 influenza vaccine was 52% effective in children, with prior vaccination offering a small benefit. No waning immunity was observed during the season.
Area of Science:
- Pediatric Infectious Diseases
- Vaccinology
- Public Health Surveillance
Background:
- The 2017-2018 influenza season exhibited high severity, necessitating annual vaccine effectiveness assessments.
- Influenza strains evolve, underscoring the need for ongoing evaluation of vaccine efficacy, particularly in pediatric populations.
- This study aimed to determine influenza vaccine effectiveness (IVE) in children and explore factors like prior vaccination and immunity waning.
Purpose of the Study:
- To estimate the influenza vaccine effectiveness (IVE) in children aged 6 months to 17 years during the 2017-2018 season.
- To assess the impact of previous influenza vaccination on current season effectiveness.
- To investigate potential intraseasonal waning of influenza vaccine immunity.
Main Methods:
- A test-negative design was employed, including children tested for influenza during the 2017-2018 season.
- Immunization status was confirmed using the Louisiana Immunization Registry.
- Vaccine effectiveness was calculated by comparing vaccination status between influenza-positive and influenza-negative cases.
Main Results:
- Overall influenza vaccine effectiveness (IVE) was 52% (38%-62%), with 49% for influenza A and 60% for influenza B.
- Children vaccinated in the current season showed the most benefit; prior season vaccination provided a small but significant benefit without interference.
- No evidence of waning vaccine immunity was detected within the 2017-2018 season.
Conclusions:
- Influenza vaccination demonstrated moderate effectiveness in children during the 2017-2018 season.
- Previous year's vaccination offered a minor but significant protective effect.
- The study found no evidence of waning immunity, highlighting the importance of continued surveillance for influenza vaccine benefits.
Background:
The 2017-2018 influenza season was of high severity. Circulating influenza strains change periodically, making it important to determine vaccine effectiveness on an annual basis, especially for susceptible populations. The primary aim of our study was to estimate the effectiveness of the influenza vaccine among children. Secondary aims were to assess the effect of previous season vaccination and intraseasonal waning of immunity.
Methods:
Children 6 months to 17 years of age tested for influenza during the 2017-2018 season were included. Clinical charts were reviewed, and immunization status was confirmed via the Louisiana Immunization Registry. Influenza vaccine effectiveness (IVE) was estimated in a test-negative design by comparing vaccination status of influenza-positive vs influenza-negative cases.
Results:
A total of 3595 children were included, 26% of whom tested positive for influenza, mostly type A (79%); 15% had received an influenza vaccine prior to illness: 8% among the influenza-positive and 17% among influenza-negative cases (P <.0001). IVE for the 2017-2018 influenza season was 52% overall (95% confidence interval, 38%-62%), 49% for influenza A, and 60% for influenza B. While receiving current year (2017-2018) vaccine had the most effect, receiving the previous year (2016-2017) vaccine had a small benefit and no interference. We found no evidence of waning immunity of the vaccine for the 2017-2018 season.
Conclusions:
IVE was moderate for children. Previous year vaccination had a small but significant benefit and there was no evidence of waning immunity in our cohort. Ongoing national and local surveillance is important to understand the benefit of influenza vaccination.
