B.C.G. Vaccination of Children against Leprosy in Uganda: Results at End of Second Follow-up

Abstract

A total of 19,169 children, all contacts or relatives of known leprosy patients, and all free of leprosy lesions, were included in a controlled trial of B.C.G. vaccination against leprosy in Uganda, and have now been followed for an average of three and a half years ; 172 cases of early leprosy lesions have so far developed among them. The great majority of the children were allocated initially by an effectively random process to a B.C.G.-vaccinated and an unvaccinated group ; 94% were seen and examined for leprosy during the first round of follow-up visits, and 91.5% during the second, with suitable precautions in both rounds to ensure unbiased assessments. The percentage reduction in leprosy incidence in the B.C.G.-vaccinated group compared with the corresponding unvaccinated group was 87%. The percentage reduction was similar for those with weak degrees of tuberculin sensitivity initially and for those with negative tuberculin reactions, and did not appear to depend upon the age at vaccination. Among those who developed leprosy lesions there was a slight tendency for the untreated lesions to progress, or to come under treatment, less frequently, and to regress more frequently, in the B.C.G.-vaccinated patients than in the corresponding group of unvaccinated patients, but the differences could well be due to chance. The incidence of leprosy in the unvaccinated children varied with their initial sensitivity to tuberculin. Those with negative tuberculin reactions had the highest subsequent incidence of leprosy, those with weak degrees of naturally acquired tuberculin sensitivity the next highest, and those with strong degrees of tuberculin sensitivity the lowest subsequent incidence of leprosy. The findings of the trial to date are consistent with the interpretation that B.C.G. confers substantial protection against early forms of leprosy, that natural tuberculosis infection also confers some protection, but that infection with non-tuberculous mycobacteria (other than the leprosy bacillus) confers little or no protection. © 1968, British Medical Journal Publishing Group. All rights reserved.