We agree with Dr Pust that our methodological and statistical analysis does not exclude the possibility that some of the variation in the results of the eight BCG trials may have been caused by biologic differences among the trials. However, when the animal data published by Palmer and Long1 were evaluated quantitatively by Hart,2 differing prevalence rates of atypical mycobacteria were regarded as an unlikely source for much of the variation in the results. Similarly, other proposed biologic explanations, such as the hypothesis that the trials differed because of the differing nutritional status of the trial populations3 or the more recent hypothesis that frequent infections with Mycobacterium tuberculosis of low virulence vitiate apparent BCG efficacy,4 lack convincing empiric demonstrations in human populations. Consequently, we do not believe that BCG should be discounted in developing countries simply because several possible—and, as yet, unknown—biologic factors may be
Clemens JD, Chuong JJH, Feinstein AR. The BCG Controversy-Reply. JAMA. 1983;250(21):2929. doi:10.1001/jama.1983.03340210026015
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