Efficacy of Pneumococcal Vaccine Questionable in Adults: Meta-Analysis

From Reuters Health Information

NEW YORK (Reuters Health) Jan 05 - Results of a meta-analysis call into question the ability of pneumococcal vaccination to prevent pneumonia in adults, even in populations for whom the vaccine is currently recommended, researchers from Switzerland and the UK conclude in a report released today.

Clinical trials have produced conflicting results on the efficacy of unconjugated pneumococcal polysaccharide vaccine in adults, Dr. Anke Huss from University of Bern and colleagues explain in the January 6 issue of the Canadian Medical Association Journal. Meta-analyses have also produced varied results depending on the trials included.

Dr. Huss and colleagues conducted a meta-analysis of 22 trials (n=101,507) that compared pneumococcal polysaccharide vaccine with a control, taking into account the methodologic quality of the trials -- something past meta-analyses have failed to do, the researchers note.

Eleven of the studies reported on instances of "presumptive pneumococcal pneumonia, 19 on all-cause pneumonia and 12 on all-cause mortality. The current 23-valent vaccine was used in 8 trials," they report.

Dr. Huss and colleagues found "little evidence of vaccine protection in trials of higher methodologic quality." The relative risk was 1.20 for presumptive pneumonia and 1.19 for all-cause pneumonia in double-blind trials.

In addition, there was little evidence of vaccine protection among elderly patients or adults with chronic illness in analyses of all trials. The relative risk was 1.04 for presumptive pneumococcal pneumonia, 0.89 for all-cause pneumonia, and 1.00 for all-cause mortality.

"The prevention of the large burden of disease associated with pneumococcal pneumonia should be a major objective from a public health perspective," Dr. Huss and colleagues note. "This will not be achieved with the use of the currently available pneumococcal polysaccharide vaccine, even allowing for a modest protective effect against invasive pneumococcal disease," they conclude.

However, the authors of an accompanying editorial caution that, "on balance, the study by Huss and colleagues does not justify ceasing pneumococcal polysaccharide vaccination of adults."

Drs. Ross Andrews and Sarah A. Moberley of the Menzies School of Health Research, Casuarina, Northern Territory, Australia, point out that the findings of this meta-analysis were noted in the current World Health Organization position paper on the 23-valent vaccine, but no change in recommendations for the use of the vaccine were made.

"The position of the World Health Organization is that randomized trials, meta-analyses of randomized trials, and most observational studies are consistent with a protective effect against invasive pneumococcal disease among healthy adults and, to a lesser extent, among individuals aged 65 years or more. In the absence of any new data to the contrary, we support that position," they conclude.

CMAJ 2009;180:18-19,48-58.