The purpose of this study was to investigate whether individuals receiving
influenza vaccines have a lower risk of
pneumonia. A nationwide population-based case-control study was conducted using data from the National Health Insurance Research Database in Taiwan. We enrolled 7565 patients each in
pneumonia and non-
pneumonia groups after diagnosis of patients with chronic
pulmonary disease, and these patients were individually age and sex matched in a 1:1 ratio. Using conditional logistic regression analysis, adjusted odds ratios (aORs) were estimated in patients who received
influenza vaccination and those who had not previously had
pneumonia. Moreover, we also analyzed the interval between vaccination and the onset of
pneumonia and the number of vaccinations received by patients. This was compared with patients who never received
influenza vaccination. Patients who had received
influenza vaccination and had been vaccinated for two consecutive years (aOR = 0.85, confidence interval (CI) = 0.79⁻0.93 and aOR = 0.75, CI = 0.67⁻0.85, respectively) showed lower rates of
pneumonia occurrence by 15⁻25%. In conclusion,
influenza vaccination significantly reduces the occurrence of
pneumonia, especially in individuals who receive vaccination in consecutive years.