BCG vaccination of children against leprosy: seven-year findings of the controlled WHO trial in Burma.

A controlled study of the efficacy of BCG vaccination for the prevention of leprosy began in Burma at the end of August 1964. This paper presents the findings after 7 years-i.e., the results of 6 annual follow-up examinations up to the end of June 1971. The incidence rate in BCG-vaccinated children 0-4 years of age at intake was lower than that in children in the control group. The protection conferred by BCG was relatively low (44%) and applied only to early cases of leprosy, the great majority tuberculoid cases. BCG vaccination did not protect household contacts or children 5-14 years of age who were not exposed in the household. This reduction must be interpreted in the light of several factors: form of leprosy, bacterial status, lepromin reactivity, evolution of cases, and level of endemicity. Consequently it does not seem probable that the reduction in incidence would substantially affect the pattern or trend of the disease in an area similar to that where the study is being carried out; the probability would be much lower if not nil in regions of relatively low endemicity (1-2 per 1 000 or less).

BCG vaccination of children against leprosy. Preliminary findings of the WHO-controlled trial in Burma.

The use of BCG vaccine in the prevention of leprosy has been one of the most important subjects of investigation in the field of leprology in the last 25 years. The action of the vaccine was for many years investigated by determining its effect on the lepromin reaction. Field studies were later considered essential to determine whether BCG vaccination would be useful to leprosy contacts, to the child population probably exposed to infection, or to persons persistently lepromin-negative.The interest of the World Health Organization in this matter began in 1952 and, following the recommendations of certain advisory committees, it was decided to institute a field trial in Singu township in Burma. The main purpose of the investigation was to observe, in a highly endemic area, the protective effect, if any, of BCG vaccine against leprosy in the child population not exposed to Mycobacterium leprae at home but possibly exposed to the infection elsewhere.Field operations began at the end of August 1964 and the preliminary findings obtained up to the end of June 1968 relate to 3 annual re-examinations. So far, from the material studied, it appears that, under the conditions prevailing in Singu township, no significant effect of BCG vaccine can be seen within a period of 3 years. When children in both trial groups are followed-up for much longer periods, mainly children aged 0-4 years at intake, it is possible that a significant difference may emerge. However, to be operationally desirable, a merely significant difference is not enough; the protective effect of BCG should be substantial to warrant its large-scale use as an immunization procedure against leprosy.