Sensitization studies with potential leprosy vaccine preparations in northern Malawi

This paper describes a comparison between BCG alone and two different doses of killed Mycobacterium leprae, with or without BCG, in stimulating skin-test sensitivity to two different soluble antigens prepared from M. leprae. Skin test conversion was assessed three months after vaccination. Significant rates of skin test conversion were stimulated by each of the vaccines to both skin test antigens, but the observed conversion rates differed markedly as measured by the two antigens. All of the vaccines caused ulcers at the site of injection in most subjects, and these local reactions are described. A combined vaccine containing 0.03 mg BCG plus 5 X 10(7) killed M. leprae induced high rates of "conversion" to both skin tests but caused local reactions slightly larger than those caused by BCG alone. The implications of these findings for selection of an optimal vaccine formulation for use in large-scale preventive trials are discussed.