Effect of influenza vaccination on post-admission outcomes for influenza patients in England: a population-based cohort study
Authors:
HPRU-EZI Authors: Neil French, Iain Buchan
Abstract:
Introduction: In the UK, adults 65 years and over and those in clinical risk groups are among those eligible for seasonal influenza vaccination. While vaccine effectiveness for reducing cases of influenza is well documented, less is known about impact on wider hospital and post-discharge outcomes in the UK. We investigated whether vaccinated adults hospitalised with confirmed influenza infection had different outcomes to non-vaccinated adults during contact with health services.
Methods: A retrospective cohort study using the Combined Intelligence for Population Health Action platform, linking primary care, secondary care and laboratory data for Cheshire and Merseyside (2.7 M population), UK. We accessed 2081 laboratory-confirmed influenza hospital admissions for adults ≥16 years (October 2018-April 2024). We studied the association of influenza vaccination with several hospital and post-discharge outcomes, considering competing risks and potential confounding factors. We included age-based subgroup analyses.
Results: Vaccination uptake was recorded as 38.8 %, 52.7 % and 20.9 % among ≥16, ≥65 and 16-64 years respectively. Among the full cohort and ≥ 65 years cohort, vaccination was associated with a reduction in length of hospital stay in competing risk models (17 %, 95 %CI 7-26 %; 19 %, 95 % CI 7-31 %), risk of death up to six months after discharge (aHR 0.66, 95 %CI 0.48-0.90; aHR 0.67, 95 %CI 0.48-0.92) and change in vaccination status in the next season (aOR 0.19, 95 %CI 0.13-0.27; aOR 0.07 95 %CI 0.04-0.13). No statistically significant difference was detected for admission to critical care or other post-discharge outcomes (readmission, attendance to general practice or emergency department).
Conclusions: Influenza vaccination was associated with benefits beyond acute illness, reducing length of hospital stay and mortality among adults hospitalised with laboratory-confirmed influenza. Findings support policy decisions, including greater outreach to high-risk, low-uptake groups and advocate for the national integration of laboratory data with comprehensive healthcare data to enable more robust vaccine evaluations.
Journal:
Vaccine