[Problems in designing a protocol for a leprosy vaccine trial. (author's transl)].

Investigations carried out by the Scientific Working Group on Immunology of Leprosy (IMMLEP) have led to the planning of field trials of an experimental vaccine preparation to be carried out in few years' time. The objectives of these trials have been defined as follows: 1) The main objective should be the assessment of the protective effect of the vaccine against leprosy, its various forms and more particularly the lepromatous form. 2) Another important objective will be to determine the value and significance of the greatest possible number of immunological tests as indicators of sensitization and as preliminary indicators of protection against leprosy, its various forms and more particularly the lepromatous form. The protocol of the trials should take into account the following points: 1) In view of the uneven distribution of leprosy, the variations in the distribution of its various forms, as well as the unknown epidemiological factors, several trials should be planned with at least one in a country in Asia or Africa and one in a country in Latin America. 2) Because of the long incubation of leprosy and its occurrence at any age, all age groups should be included in the trials. 3) To take into account the low incidence of leprosy, the trials should involve a large population and the observation period should last about ten years. 4) In view of the low incidence of leprosy and its uneven distribution, the random sampling for allocation to vaccinated and control groups should be based on individuals. 5) Because of the absence of objective criteria for the diagnosis of leprosy, provision should be made in the protocol to minimize over- and under-diagnosis. 6) When the immunological tests to ber studied within the protocol itself may affect the results of the trial, special groups should be planned for these investigations.