January 5, 2009
NEW YORK (Reuters Health) – The ability of standard pneumococcal vaccination to prevent pneumonia in adults, even those for whom the vaccine is currently recommended, is called into question by researchers from Switzerland and the UK in a report released Monday.
There are two main types of vaccine targeting the pneumococcus microbe. The standard product incorporates fragments of various sugars (polysaccharides) from the coating of 23 strains of pneumococcus, but it does not greatly stimulate the immune system to attack invading bacteria. In the other vaccine, the sugars from seven pneumococcal strains are bound to a diphtheria toxin, and the resulting “conjugate” vaccine triggers a stronger immune response.
Clinical trials have produced conflicting results on the efficacy of the so-called unconjugated pneumococcal polysaccharide vaccine in adults, Dr. Anke Huss from the University of Bern and colleagues explain in the Canadian Medical Association Journal.
They conducted an analysis of pooled results from 22 trials involving a total of more than 100,000 subjects. The team found “little evidence of vaccine protection” in trials judged to be of higher quality. In addition, there was little evidence of vaccine protection among elderly patients or adults with other chronic illness in analyses of all trials.
Preventing “the large burden of disease” associated with pneumonia “will not be achieved with the use of the currently available pneumococcal polysaccharide vaccine,” the investigators 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 World Health Organization takes the position that results of clinicals trials and analyses of these trials 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.”
They conclude, “In the absence of any new data to the contrary, we support that position.”
SOURCE: Canadian Medical Association Journal, January 6, 2009.
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