Additive benefits of pneumococcal and influenza vaccines among elderly persons aged 75 years or older in Taiwan - A representative population-based comparative study

Objective: It remains unclear whether pneumococcal vaccine provides additional protection to the elderly who have already vaccinated with influenza vaccine. This retrospective cohort study aimed to assess the additive effect of pneumococcal and influenza vaccines on the risk of mortality, hospitalization, and inpatient expenditure in the elderly aged 75 years or older in Taiwan. Methods: Data were extracted from the National Health Insurance claims data of a nationally representative elderly sample. To reduce potential selection bias, we employed a propensity score matching method to classify the vaccination status into 3 groups. Multivariable logistic and linear regression models were used to compare the outcomes among different groups. Results: Each group contained 8142 subjects. The results indicated that an additive effect of receiving both vaccines was associated with a significantly lower all-cause mortality (relative risk [RR]: 0.74; 95% confidence interval [CI]: 0.57-0.96), hospitalization of all diseases including pneumonia, influenza, chronic obstructive pulmonary disease, respiratory diseases, and congestive heart disease (RR: 0.77; 95% CI: 0.67-0.90), and a 13% reduction (95% CI: 0.81-0.94) in inpatient expenditures of all diseases when compared with receiving influenza vaccine alone. Conclusions: This study confirmed that vaccination of elderly individuals with pneumococcal vaccine and influenza vaccine concomitantly has substantial beneficial effects.