Impact of 23-valent pneumococcal polysaccharide vaccination on the frequency of pneumonia-related hospitalization and survival in elderly patients with prostate cancer: A seven-year nationwide matched cohort study

Background: The 23-valent pneumococcal polysaccharide vaccine (PPSV23) is indicated for adults who have a high risk of pneumonia; however, its effectiveness in patients with prostate cancer who are at a risk of pneumonia because of age and cancer treatments, including androgen-deprivation therapy, is unknown. Methods: Between 2000 and 2010, 38,735 patients with prostate cancer were diagnosed in Taiwan. After exclusions and exact matching for age, previous pneumonia, and influenza vaccination, 2188 vaccinated patients and 2188 unvaccinated patients were recruited. The incidence density of all-cause bacterial pneumonia hospitalizations was analyzed. Results: Over 7 years of follow-up, patients who received the PPSV23 had a significantly lower incidence density, with 142.8 per 1000 person-years versus 162.0 per 1000 person-years for unvaccinated patients. More patients in the vaccinated cohort were never hospitalized for pneumonia compared with those in the unvaccinated cohort (64.2% vs 62.2%, respectively). After adjusting for the Charlson comorbidity index, cancer treatment modalities, and socioeconomic levels, the risk of pneumonia-related hospitalization in the PPSV23 vaccination cohort was 0.48 times lower than that in the unvaccinated cohort (adjusted incidence rate ratio, 0.48; P =.046). For patients who received the influenza vaccination, subgroup analysis demonstrated that PPSV23 vaccination significantly decreased the risk (adjusted incidence rate ratio, 0.45; P <.001). Compared with unvaccinated controls, PPSV23-vaccinated patients had a lower cumulative incidence for the first occurrence of pneumonia-related hospitalization (34.49% vs 36.36%; P =.178) and higher overall survival (47.5% and 42.3%, respectively; P <.001). Conclusions: Vaccination of elderly patients who have prostate cancer with the relatively common and inexpensive PPSV23 can decrease the risk of pneumonia and prolong survival.