Effectiveness of Influenza Vaccination in Reducing Hospitalization and Mortality Among Adults

Abstract

Introduction: Influenza remains a major public health concern, leading to substantial morbidity, mortality, and economic burden, particularly among adults with comorbidities and the elderly. Annual vaccination is the most effective preventive measure, yet its effectiveness varies by viral strain match, age, and immune status. This meta-analysis evaluated influenza vaccination effectiveness in reducing hospitalization, ICU admission, and mortality in adults.

Methods: This systematic search of PubMed, Scopus, Web of Science, and Google Scholar has been performed up to 2024, following PRISMA guidelines. Inclusion criteria were adult populations (≥18 years) receiving seasonal influenza vaccination with outcomes of hospitalization, ICU admission, or mortality. Five studies (case-control and cohort designs) were included. Data were extracted independently, and study quality was evaluated via the Newcastle–Ottawa Scale. Odds ratios with ninety-five percent confidence intervals have been estimated utilizing fixed- or random-effects models based on heterogeneity (I²).

Results: Across studies, influenza-positive patients exhibited higher ICU admission rates than influenza-negative patients. Pooled analysis showed no significant difference in ICU admission (mean difference 4.45, 95% CI: 2.27–8.73, P=0.00001). Mortality analysis revealed significantly lower death rates among vaccinated or influenza-positive adults (mean difference 5.20, 95% CI: 2.26–11.97, P=0.0001). Heterogeneity has been observed for both outcomes (I² = 86–87%).

Conclusion: Influenza vaccination is related to decreased death and mitigates severe disease outcomes in adults. These results reinforce the importance of annual vaccination programs to decrease hospitalizations and prevent death among adult populations.