To the Editor.—
In their rigorous critique of the methodology of the eight large BCG trials, Clemens and colleagues go far in clarifying "The BCG Controversy" (1983;249:2362). Yet, while briefly noting potential nonmethodological sources of efficacy variation, they fail to emphasize that the three high (≥75%) efficacy trials (in England and Chicago and among Western US Indians) were unique in sharing not only unbiased design but a relative absence of nontuberculous mycobacterial sensitivity in their geographic areas. Although early infection with atypical mycobacteria, highly prevalent in all of the "low-efficacy" trial areas, cannot explain negative BCG efficacy, such atypical mycobacteria infections may account for a large proportion of the difference between 0% and 75% to 80% efficacy.1The narrow confidence interval of the three high-efficacy results rectly rectly establishes that BCG can be— and has been—highly effective in these geographic areas and populations. But we should not be left
Pust RE. The BCG Controversy. JAMA. 1983;250(21):2928–2929. doi:10.1001/jama.1983.03340210026014
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