One-hundred-seventy-nine
lepromin-negative household contacts were vaccinated with heat-killed Mycobacterium leprae, BCG, or a combination of the two. Vaccination induced
lepromin positivity in 131 of these contacts. Over an 8-year follow-up period, 12
lepromin-positive contacts developed
leprosy, all tuberculoid; while 2
lepromin-negative vaccinated contacts developed
leprosy, both lepromatous. Overall, 7.8% of the vaccinated contacts developed the disease. Seven-hundred-fourteen household contacts were not vaccinated, and served as controls. Among the 504 who were
lepromin positive,
leprosy developed in 35, all tuberculoid, over the 8-year follow up. Among the 210
lepromin-negative unvaccinated contacts, 61 developed
leprosy: tuberculoid in 29, borderline in 4, lepromatous in 8, and indeterminate in 20. Overall, 13.5% of the 714 unvaccinated contacts and 29.0% of the 210 unvaccinated,
lepromin-negative contacts developed
leprosy. Vaccination could not induce
lepromin positivity in all contacts. The three
vaccines were equally effective in inducing
lepromin positivity. Vaccination reduced the overall incidence of
leprosy from 13.5% to 7.8% among household contacts but did not reduce the incidence of
lepromatous leprosy (1.2% of all the vaccinated and 1.1% of all the unvaccinated contacts).