BCG revaccination does not protect against leprosy in the Brazilian Amazon: a cluster randomised trial.

Background: Although BCG has been found to impart protection against leprosy in many populations, the utility of repeat or booster BCG vaccinations is still unclear. When a policy of giving a second BCG dose to school children in Brazil was introduced, a trial was conducted to assess its impact against tuberculosis, and a leprosy component was then undertaken in parallel.

Objective: to estimate the protection against leprosy imparted by a second dose of BCG given to schoolchildren.

Neonatal BCG protection against tuberculosis lasts for 20 years in Brazil.

Bacille Calmette-Guérin (BCG) efficacy against pulmonary disease is highly variable; until very recently there was no evidence of protection after 10 years. In the control arm of a trial of efficacy of revaccination of schoolchildren in Brazil we found substantial protection (39%; 95%CI 9-58) of neonatal BCG against all forms of tuberculosis (TB) 15-20 years after vaccination, much longer than previously believed. This confirms recent findings from an earlier trial, and must be considered in the design of trials of new TB vaccines and in policy decisions based on assumed lack of neonatal BCG protection with time.

Design of the leprosy component of the Brazilian BCG revaccination trial for assessing BCG effectiveness against leprosy in school children.

Background: BCG vaccination confers protection against leprosy, and vaccination among household contacts has been recommended in Brazil. Nevertheless, vaccination of the entire community against leprosy is not advocated as leprosy has low incidence in most populations. Despite that, in Brazil, BCG vaccination is recommended among school children to prevent tuberculosis and this large scale vaccination may also affect the occurrence of leprosy, which led to investigations of its impact on leprosy in endemic areas of Brazil.