The 23-valent pneumococcal polysaccharide vaccine. Part I. Efficacy of PPV in the elderly: a comparison of meta-analyses.

A 23-valent polysaccharide pneumococcal vaccine (PPV) has been available in the UK for more than 20 years and is currently recommended for use in high-risk groups (HRG) of 2+ years of age. The degree of protection afforded by the PPV remains a critical issue, although a number of randomised clinical trials and case-control studies (CCS) have been published. The aim of this work is to review the estimates on the efficacy of PPV against pneumococcal pneumonia and invasive pneumococcal disease (IPD) in the elderly and to perform a meta-analysis in order to obtain a pooled estimate of the level of protection in high and low risk individuals. These two groups of individuals are at the centre of the current debate on whether or not to extend the vaccination programme to all elderly individuals 65+. Only randomised and quasi-randomised studies are included in the analysis and results are compared with previous meta-analyses. The effect of the inclusion of observational studies is investigated in the sensitivity analysis. When taken with the results of other meta-analyses and observational studies, it appears that PPV offers protection against IPD in the general elderly population (VE = 65%; 95% CI: -49-92%) whereas it has a moderate effect in the high-risk elderly (VE = 20%; 95% CI: -188-78%). The vaccine has little or no effect against pneumonia (VE = 16% in the general elderly and -20% in HRG).