Big data analysis of influenza vaccination and liver cancer risk in hypertensive patients: insights from a nationwide population-based cohort study

Background: previous studies have indicated that influenza vaccination may be associated with reduced risks of certain types of cancer. However, the protective effect of influenza vaccination against primary liver cancer in individuals with hypertension remains unclear. Methods: In this cohort study, 37,022 patients over 55 years of age who received a diagnosis of hypertension at any time between January 1, 2001, and December 31, 2012, were enrolled from the National Health Insurance Research Database. The patients were divided into a vaccinated and an unvaccinated group. Categorical and continuous variables were analyzed using the chi-square test and t test, respectively, and the correlation between influenza vaccination and liver cancer in patients with hypertension was analyzed using time-varying COX model. Propensity score method was performed to reduce selection bias. Results: Compared with the unvaccinated group, the vaccinated group had a significantly lower incidence of liver cancer (hazard ratio = 0.56, 95% confidence interval = 0.46–0.64; p <.001). In addition, a protective effect was observed regardless of sex, age, or comorbidities. Besides, the association was dose-dependent which could be noted when patients were stratified based on the total number of vaccinations. The adjusted HRs for patients receiving 1, 2 to 3, and ≥ 4 vaccinations during the follow-up period were 0.60 (0.51–0.78), 0.48 (0.38–0.65), and 0.39(0.30–0.51), respectively. Conclusions: In summary, influenza vaccination is linked to a decreased risk of liver cancer in individuals with hypertension. However, unmeasurable confounders may have been present in the analysis.