Effect of annual influenza vaccination on reducing lung cancer in patients with chronic obstructive pulmonary disease from a population-based cohort study

Chronic obstructive pulmonary disease (COPD) patients are at a higher risk of development of lung cancer. Frequent exacerbations of COPD trigger the disease course to chronic inflammation which likely plays a role in the pathogenesis of lung cancer. Previous studies showed influenza virus infection is one of important causes for exacerbations of COPD. Therefore, the aim of this study was to know whether influenza vaccination could reduce the incidence of lung cancer in patients with COPD. This cohort study enrolled patients (≥55 years old) with a recorded diagnosis of COPD between January 1, 2000 and December 31, 2012 by using the Taiwan Health Insurance Database. A propensity score was calculated to reduce vaccine therapy selection bias. Cox proportional hazard regressions were used to investigate the association between the influenza vaccination and lung cancer incidence after adjusting for known confounding factors. Besides, we categorized the patients into 4 groups according to vaccination status (unvaccinated, total number of vaccinations: 1, 2–3, ≥4) to evaluate the dose-dependent effect on reducing lung cancer occurrence of lung cancer in COPD patients. Our study comprised of 28,752 eligible individuals from the COPD cohort database. Among them, 51% (14,630) received influenza vaccination; the rest (49%) of the COPD patients did not receive influenza vaccination. We observed that COPD patients receiving influenza vaccination had a lower risk of lung cancer (adjusted HR = 0.40, 95% CI (0.35–0.45), P < .001). We also founded comparable protective effect in both sexes and all age groups (55–64, 65–74, ≥75) regardless of influenza seasonality. Furthermore, dose-dependent protective effect could be seen after stratifying patients according to the total number vaccinations, the adjusted HRs for lung cancer risk were 0.48 (0.40–0.54) and 0.24 (0.20–0.29) for patients who received 2 to 3 and ≥4 vaccinations during the follow-up period. This population-based cohort study demonstrated that annual influenza vaccination administration could reduce incidence of lung cancer in COPD patients.