Commonly used pneumococcal polysaccharide vaccines do not appear to be effective for preventing pneumonia, found a study by a team of researchers from Switzerland and the United Kingdom writing in the Canadian Medical Association Journal.

In many industrialized countries, polysaccharide pneumococcal vaccines (PPVs) are currently recommended to help prevent pneumococcal disease in people aged 65 and over and for younger people with increased risk due to conditions like HIV. Studies have shown conflicting results regarding the efficacy of PPV. 

The study, a systematic review and meta-analysis, looked at 22 clinical trials, reviews and meta-analyses and more than 100,000 participants from countries in North America as well as India, Africa, Latin America and the Caribbean. Unlike other similar studies the authors examined the reasons why different clinical trials produced different results. They found that the quality of the studies substantially affected the results. When only high quality trials were included, there was no evidence that PPVs could prevent pneumonia. The study adds to the ongoing debate around effectiveness of the vaccine.

"Policy makers may therefore wish to reconsider their current recommendations for PPV, especially where routine pneumococcal conjugate immunization has been introduced," conclude Dr. Matthias Egger from the University of Bern, Switzerland and coauthors. 

However, in a related commentary, Dr. Ross Andrews and coauthor from the Menzies School of Health Research, Darwin, Australia state that the researchers' conclusions exceed the evidence presented. They caution that there should be no change in vaccine policy in countries that recommend PPV to prevent invasive pneumococcal disease.


Anke Huss, Pippa Scott, Andreas E. Stuck , Caroline Trotter, Matthias Egger, 'Efficacy of pneumococcal vaccination in adults:a meta-analysis', CMAJ JANUARY 6, 2009  180(1)

Ross Andrews, Sarah A. Moberley, 'The controversy over the efficacy of pneumococcal vaccine', CMAJ JANUARY 6, 2009  180(1)