BCG protection against Mycobacterium tuberculosis infection by level of exposure in The Gambia.

In Indonesia, BCG protection against M. tuberculosis infection decreased with increasing exposure to the pathogen. We aimed to validate these findings in Africa. Poisson regression was used to estimate BCG protection, stratified by exposure using an exposure score, against ELISPOT conversion at 3 months in 220 Gambian case contacts. While the interaction between BCG and exposure was not significant (p=0.13), BCG protection was strongest in the lowest exposure tertile (RR, 0.35 [95% CI,0.15-0.82]; P=0.02), and the RRs for the middle and highest tertile were 0.50 (0.30-0.83; P=0.008) and 0.71 (0.45-1.13; P=0.1) respectively. These results are consistent with those from Indonesia.