Post-vaccination sensitization with ICRC vaccine.

ICRC vaccine is one of the candidate anti-leprosy vaccines under test in a large scale comparative vaccine in trial. The objectives of the present study was to study the sensitization potential, as measured by Rees' MLSA and lepromin, and reactogenicity of this vaccine preparation in the local population. The study included 368 'healthy' individuals aged 1-70 years. Each individual received either ICRC vaccine or normal saline (control) by random allocation. They were also tested with Rees' MLSA and lepromin-A, 12 weeks after vaccination. Reactions to Rees' MLSA were measured after 48 hours and those to lepromin-A after 48 hours and three weeks. Character and size of local response, at the vaccination site, were recorded at 3rd, 8th and 15th week after vaccination. The results of the study showed that healing of vaccination lesion was uneventful, the mean size of the lesion being 10.3 mm. The mean sizes of post-vaccination reactions, to Rees' MLSA and lepromin (both early and late reactions), were significantly higher in the vaccine group compared to that in the normal saline group; the sensitizing effect attributable to the vaccine was of the order of 3.5 mm, 1.7 mm and 2.2 mm respectively. In conclusion, the study has demonstrated that ICRC vaccine was 'safe' and produced significant sensitizing effect as measured by post-vaccination sensitization to Rees' MLSA and lepromin, in the local population.