Efficacy of 23-valent pneumococcal polysaccharide vaccine in preventing community-acquired pneumonia among immunocompetent adults: A systematic review and meta-analysis of randomized trials

Background: Data on the efficacy of the 23-valent pneumococcal polysaccharide vaccine (PPV-23) in preventing adult community-acquired pneumonia (CAP) among the target population of individuals aged over 65 years and high-risk individuals aged 19-64 years are conflicting. As the Advisory Committee on Immunization Practices (ACIP) has recently demonstrated PPV-23 is likely beneficial to immunocompromised adults by the Grading, Assessment, Development, and Evaluation (GRADE) framework, we conducted meta-analysis to examine its efficacy in an immunocompetent population. Methods: We searched the PUBMED, EMBASE, and Cochrane Library databases for randomized trials. Overall relative risks (RRs) with 95% confidential intervals (CIs) were calculated, and the Cochrane Q test (p, I2) was performed. Outcomes were assessed by the GRADE framework. Results: Seven randomized trials involving 156,010 participants were included in this meta-analysis. High-quality evidence revealed that PPV-23 was weakly associated with the prevention of all-cause pneumonia ([RR] 0.87, [95%CI] 0.76-0.98, p = 0.11, I2 = 43%), especially among the target population ([RR] 0.72, [95%CI] 0.69-0.94, p = 0.58 I2 = 0%), the elderly group aged over 40 years ([RR] 0.80, [95%CI] 0.69-0.94) and the Japanese population ([RR] 0.72, [95%CI] 0.59-0.88, p = 0.24, I2 = 30%). The target population included adults aged over 65 years and patients at high risk of pneumonia due to chronic lung disease, chronic obstructive pulmonary disease or living in a nursing home. Protective trends of PPV-23 in the outcomes of pneumococcal pneumonia ([RR] 0.54, [95%CI] 0.18-1.65, p = 0.01, I2 = 77%) and mortality due to pneumonia ([RR] 0.67, [95%CI] 0.43-1.04, p = 0.67, I2 = 0%) were observed, although the results were statistically insignificant, possibly due to the small number of trials included. PPV-23 did not prevent all-cause mortality ([RR] 1.04, [95%CI] 0.87-1.24, p = 0.95, I2 = 0%). Conclusions: PPV-23 provided weak protection against all-cause pneumonia in an immunocompetent population, especially among the target population. The additional benefit of PPV-23 in preventing CAP further supports its application in the target population. Copyright © 2016 Elsevier Ltd.