Are Pneumococcal Vaccine Useless ????????????

kinsley's picture

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.

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.

Dr. Ross Andrews and others 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.

WHAT IS YOUR OPINION ON THIS RECENT META-ANALYSIS AND SYSTEMATIC REVIEW?

Reference:
Huss A, Scott P, Stuck AE, Trotter C, Egger M.
Efficacy of pneumococcal vaccination in adults: a meta-analysis.
CMAJ. 2009 Jan 6;180(1):48- 58.
http://www.cmaj.ca/cgi/content/full/180/1/48

For further information contact:
Dr. Matthias Egger,
Institute of Social and Preventive Medicine,
University of Bern,
Finkenhubelweg 11,
CH-3012 Bern,
Switzerland

Fax: 41 31 631 35 20
E-mail: egger@ispm.unibe. ch

Comments

asharma's picture

Are Pneumococcal Vaccine Useless ????????????

The same issue of CMAJ contained a detailed critique of this particular meta-analysis by Ross Andrews and Sarah A. Moberley, authors of the recent Cochrane review of the same meta-literature. Their objections were in some cases quite general, arguing that the conclusions went far beyond the available data (e.g. it is one thing to say that the analysis failed to show a benefit, but quite another to imply that vaccine might actually increase risk). That said, there were a number of specific concerns which they also identified. Among the more glaring were:

1) Confidence intervals were extremely wide for efficacy against invasive pnemococcal disease:

"...definitive pneumococcal pneumonia (95% CI 0.05– 8.61) and bacteremia (95% CI 0.46–1.77). These were rare events in the evaluated clinical trials, with only 7 cases of definitive pneumococcal pneumonia from 2 studies (n= 794) and 44 cases of bacteremia from 6 studies (n= 32770) trial"

2) Inconsistent exclusion of studies

".. They excluded Kaufman’s trial as not being truly randomized because a substantial number of individuals were said to have volunteered to be vaccinated. However, there is no information in the published report to this effect; indeed, Kaufman states that people were “selected at random” each year in the pneumonia season....that was not a basis for its exclusion"

"The study by Honkanen and colleagues should have been excluded ..., because it allowed subjects to choose which vaccine they received...The basis for excluding the study by Riley and colleagues is also questionable."

3) Inconsistent or imprecise diagnostic criteria

"The specificity of radiologically confirmed pneumonia is questionable, but their undefined classification of “typical clinical” pneumonia seems even more unreliable. Huss and colleagues rightly note concerns about the specificity of presumptive pneumococcal pneumonia, but the same could be said for all-cause pneumonia. "

Andrews and Moberly raised some serious and sober concerns, and I suspect that they are correct in asserting that there is little to be gained by continuing to re-analyze the same literature (this being the 12th meta-analysis of essentially the same body of studies, differing primarily in which studies were included for systematic analysis). So while this particular review might raise some issues to be addressed in future trials, I'm not sure I am prepared to throw out the baby with the bathwater, just yet :)

A. Sharma MD, FRCP(C)
Montreal

asharma's picture

pneumococcal vaccine

Addendum to earlier reply:

In discussing the question posed by kinsley, a couple of other points have been brought to my attention by an ID colleague more knowledgeable than myself. I pass these on as perhaps of interest to the author of the original post.

First, it's easy to dismiss observational studies as at "risk of potential bias", but studies like that of Shapiro et al (reference 54) are very well done. They are of far better quality then some so called "controlled" studies.

Second, current PPV23 recommendations for the elderly recommend only one dose. The reason is the often painful reaction to the repeat dose. But this makes no sense if one looks at how PPV23 works. It has no immunological memory after 3-5 years. In order for PPV23 to continue to work, one has to revaccinate at least every 5 years (there is no booster effect).

Third, herd immunity effect of children vaccinated with PCV7 on invasive pneumococcal infections in the elderly far exceeded that of any PPV23 vaccination campaign i.e. a 37% drop since the introduction of PCV7 in the US; http://www.sabin.org/files/Cynthia%20Whitney%204pneumo.pdf; also referenced in this citation is an extremely well done observational study on the effect of PCV7/herd immunity in children with SCD. But there was an increase in non PCV7 vaccine serotypes, though fortunately many of them are part of the polyvalent PPV23).

Thanks to Tim for these additional comments (he's shy :).

A. Sharma (Montreal)

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