BCG vaccination of children against leprosy in Uganda: final results

Abstract

SummaryA total of 19200 children, all contacts or relatives of known leprosy patients, and all free of visible leprosy lesions, were included in a controlled trial of BCG vaccination against leprosy in Uganda between 1960 and 1964. They were followed for an average of 8 years, during which time 261 developed early leprosy lesions. A less comprehensive follow-up was carried out for a further 5 years, when 8 more cases of leprosy were identified.In the main intake, between 1960 and 1962, 16150 tuberculin-negative or weakly tuberculin-positive (Heaf Grades O-II) children were allocated by an effectively random process to either a BCG-vaccinated or an unvaccinated control group. Both groups were seen and examined in an identical fashion for leprosy at approximately 2-year intervals, and precautions were taken to ensure unbiased assessment of new cases of leprosy. After 8 years, 41 cases of leprosy had been identified in the BCG-vaccinated group, and 201 in the control group, a percentage reduction in the BCG-vaccinated group compared with the control group of 80%. The percentage reduction was similar for those initially tuberculin-negative, and for those initially weakly positive, and did not depend upon the age at vaccination. It was also similar for both sexes, for contacts of lepromatous and contacts of non-lepromatous leprosy, for children having contact with one or more than one patient, and for differing grades of physical contact and genetic relationship with a patient. The protective effect of BCG vaccination continued over the 8-year period, although it may have fallen off slightly at the end.In a group of 1074 strongly tuberculin-positive (Heaf Grades III-IV) children followed in parallel with the other two groups a total of 16 cases of leprosy were identified. When adjusted for age, this incidence is 58% lower than that in the unvaccinated control children who were initially tuberculin-negative, indicating a protective effect against leprosy of naturally-acquired strong tuberculin sensitivity.Between 1970 and 1975, one new case of leprosy was identified in a child who had initially been strongly tuberculin-positive and had therefore not been vaccinated, one in a BCG-vaccinated child, and 6 in control children. Although the follow-up in this period was less comprehensive than that in the main part of the trial, the ascertainment of cases was unlikely to have been biased towards either vaccinated or control children. These results indicate a continuing protective effect of BCG up to 12–13 years after vaccination.