Effectiveness of vaccination on influenza-related critical illnesses in the elderly population

Objectives: The prevention of serious influenza-related severe conditions due to influenza is important, particularly in elderly patients, age is a risk factor for death resulting from influenza-related respiratory diseases. The aim of the present study was to investigate the association of influenza vaccination with severe condition requiring critical care and death in elderly people, using vaccine records and healthcare administrative claims data in a Japanese city.Results: Among 5608 patients aged =65 years diagnosed with influenza, we identified 96 patients who had received invasive mechanical ventilation or died. Thereafter, we matched 384 controls with the cases. The cases were less vaccinated than the controls (37.5% vs. 56.0%, P < 0.01). In the multivariate analysis, influenza vaccination was associated with a lower proportion of the composite outcome (odds ratio, 0.35; 95% confidence interval, 0.21-0.60). In patients aged =80 years old and those with cardiovascular disease, influenza vaccination was associated with low composite outcomes.Conclusions: Influenza vaccination was associated with reduced proportions of receiving invasive mechanical ventilation or influenza-related mortality, particularly in those aged =80 years old.