Comparative leprosy vaccine trial in south India.

This report provides results from a controlled, double blind, randomized, prophylactic leprosy vaccine trial conducted in South India. Four vaccines, viz BCG, BCG+ killed M. leprae, M.w and ICRC were studied in this trial in comparison with normal saline placebo. From about 3,00,000 people, 2,16,000 were found eligible for vaccination and among them, 1,71,400 volunteered to participate in the study. Intake for the study was completed in two and a half years from January 1991. There was no instance of serious toxicity or side effects subsequent to vaccination for which premature decoding was required. All the vaccine candidates were safe for human use. Decoding was done after the completion of the second resurvey in December 1998. Results for vaccine efficacy are based on examination of more than 70% of the original "vaccinated" cohort population, in both the first and the second resurveys. It was possible to assess the overall protective efficacy of the candidate vaccines against leprosy as such. Observed incidence rates were not sufficiently high to ascertain the protective efficacy of the candidate vaccines against progressive and serious forms of leprosy. BCG+ killed M. leprae provided 64% protection (CI 50.4-73.9), ICRC provided 65.5% protection (CI 48.0-77.0), M.w gave 25.7% protection (CI 1.9-43.8) and BCG gave 34.1% protection (CI 13.5-49.8). Protection observed with the ICRC vaccine and the combination vaccine (BCG+ killed M. leprae) meets the requirement of public health utility and these vaccines deserve further consideration for their ultimate applicability in leprosy prevention.

Studies on rapid assessment methods in leprosy.

A study was undertaken in Pudukottai district, Tamilnadu, India to test rapid assessment methods: viz (i) sample surveys with lower coverages for clinical examination in estimating the disease problem in the community, (ii) utility of registered case prevalence for estimating the actual prevalence in a given area, (iii) leprosy in school-going children and its utility in estimating leprosy prevalence in the community, and (iv) information on disability and smear positivity in estimating leprosy prevalence; and develop correction factors for estimating leprosy situation. A sample of 23 clusters from 582 clusters of contiguous villages and hamlets was further divided into two random sub-samples for two surveys with differing coverages. One team covered nine clusters comprising 34 villages with a population of 17,562 and examined 15,596 with a population of 26,927 and examined 16,622 (62%) persons for leprosy. The results showed that: (i) leprosy sample surveys with lowered coverages would tend to miss valuable information, in terms of quality and quantity; (ii) from 'known case' registers, to estimate the true burden of leprosy disease and to monitor its trend over time is inadequate; (iii) school surveys are of limited value for estimating the disease burden in the community or to monitor its trend over time; (iv) the number of smear-positive cases is to small to serve as an indicator for the total case load in the community; and (v) the prevalence of active disease and that of grade 2 disability in the community are poorly correlated. Reliable methods other than those used here need to be developed for evaluation and monitoring of the disease burden particularly in the post-MDT era.