Vaccines for preventing pneumococcal infection in adults

Diseases caused by Streptococcus pneumoniae(S. pneumoniae) continue to cause substantial morbidity and mortality throughout the world. Whilst pneumococcal polysaccharide vaccines (PPV) have the potential to prevent disease and death, the degree of protection afforded against various clinical endpoints and within different populations is uncertain.

To assess the effectiveness of PPV in preventing disease or death in adults. Adverse events were not assessed.

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2007, Issue 2); MEDLINE (January 1966 to June 2007); and EMBASE (1974 to June 2007).

A) Randomised controlled trials (RCTs) comparing PPV with placebo, control vaccines, or no intervention.B) Non-RCTs assessing PPV effectiveness against invasive pneumococcal disease (IPD).

A) RCTs: trial quality assessment was conducted by two review authors and data extracted by three authors; odds ratios (OR) and 95% confidence intervals (CI) were estimated using a random-effects model.B) Non-RCTs: study quality, including measures to control for confounding, was assessed and data extracted by two review authors; OR and 95% CI were calculated using a random-effects model following the conversion of each study outcome to a log OR and standard error.

Twenty-two studies met our inclusion criteria (15 RCTs involving 48,656 participants and 7 non-RCTs involving 62,294 participants). Meta-analysis of the RCTs found strong evidence of PPV efficacy against IPD with no statistical heterogeneity (OR 0.26, 95% CI 0.15 to 0.46; random-effects model, I-squared (I(2)) = 0%). Efficacy against all cause pneumonia was inconclusive with substantial statistical heterogeneity (OR 0.71, 95% CI 0.52 to 0.97; random-effects model, I(2) = 87.3%). PPV was not associated with substantial reductions in all-cause mortality (OR 0.87, 95% CI 0.69 to 1.10; random-effects model, I(2) = 75.3%). Vaccine efficacy against primary outcomes appeared poorer in adults with chronic illness but the difference was not statistically significant. Non-RCTs provided evidence for protection against IPD in populations for whom the vaccine is currently utilised (OR 0.48, 95% CI 0.37 to 0.61; random-effects model, I(2) = 31.4%).

This meta-analysis provides evidence supporting the recommendation for PPV to prevent IPD in adults. The evidence from RCTs is less clear with respect to adults with chronic illness. This might be because of lack of effect or lack of power in the studies. The meta-analysis does not provide compelling evidence to support the routine use of PPV to prevent all-cause pneumonia or mortality.