Effectiveness of a 23-valent Pneumococcal Polysaccharide Vaccine for the Prevention of Pneumococcal Pneumonia in the Elderly with Chronic Respiratory Diseases: A Case-control Study of a Single Center

Background: The effectiveness of the 23-valent pneumococcal polysaccharide vaccine (PPSV23) in preventing non-invasive pneumococcal pneumonia (non-IPD) has been controversial. Methods: : To evaluate the effectiveness of the PPSV23 in elderly outpatients with chronic respiratory diseases, we carried out a case-control study, including 4128 outpatients aged ≥ 65 years, in the respiratory department. Results: : There were 320 vaccinated patients, of which 164 were diagnosed with pneumococcal pneumonia. The adjusted odds ratio was 0.39 (95 % confidence interval (CI), 0.17 to 0.89). In the subsets consisting of age groups ≥ 70 and ≥ 75 years, the adjusted odds ratio (95 % CI) was respectively 0.16 (0.04 to 0.67) and 0.15 (0.02 to 1.12). Conclusion: This real-world study suggests that PPSV23 is effective in preventing pneumococcal pneumonia in the elderly with chronic respiratory diseases and in the older population (age ≥ 75 years).