Effect of Measles Vaccination on Disease Severity and Complications: A Systematic Review and Meta-Analysis

Abstract

Background: Measles remains a highly contagious vaccine-preventable disease-causing substantial morbidity and mortality, particularly among unvaccinated and under-vaccinated populations. Declining immunization coverage, vaccine hesitancy, and post-pandemic disruptions highlight the need to assess the association between vaccination status and measles severity, complications, and clinical outcomes.

Objectives: To evaluate the effects of measles vaccination on disease severity and complications among infected individuals.

Methods: This systematic review and meta-analysis adhered to PRISMA guidelines. The study included patients diagnosed with measles and compared clinical severity and complications between vaccinated and unvaccinated individuals. A comprehensive search of PubMed, Scopus, EBSCO Host, and the Cochrane Library was conducted to identify observational studies comparing clinical outcomes between the two groups. Pooled odds ratios (ORs) with 95% confidence intervals were calculated using a random-effects model, and heterogeneity was assessed using the I² statistic.

Result: Of 2,661 identified records, after removing duplicates (n=765) and screening (n=1860), 14 out of 36 studies met eligibility criteria for final analysis. Measles vaccination was linked to reduced odds of hospitalization (OR 0.58, 95% CI 0.42–0.81), severe disease (OR 0.53, 95% CI 0.33–0.85), complications (OR 0.62, 95% CI 0.51–0.75), and pneumonia (OR 0.63, 95% CI 0.50–0.80), but not encephalitis (OR 1.95, 95% CI 0.67–5.66) nor mortality (OR 0.50, 95% CI 0.13–1.82). Heterogeneity ranged from low to substantial, especially for hospitalization and severe disease.

Conclusion: Measles vaccination significantly reduces severe outcomes and complications, underscoring its important role in disease prevention and severity reduction while reinforcing the need for stronger global immunization efforts.