The effect of Bacille Calmette-Guérin vaccine on tuberculin reactivity in indigenous children from communities with high prevalence of tuberculosis.

ABSTRACT

The Bacille Calmette-Guérin (BCG) vaccine is the most widely used vaccine in the world, however it may cause problems for the appropriate interpretation of the tuberculin skin test (TST). We assessed the diagnostic value of latent infection in vaccinated and unvaccinated indigenous children from communities that have a very high prevalence of adult tuberculosis (TB). A total of 997 children under 15 years old and classified in age groups (0-1.9, 2-5, 6-9 and 10-15 years old) were randomly selected and given TSTs using the Mantoux technique. TST induration values of vaccinated children (n=724) were compared with those of children unvaccinated (n=273). BCG vaccination was not an important cause of false-positive TST, except in communities with a low prevalence of active TB. In conclusion, the results suggested that a history of BCG vaccination on TST+ response after 10 years of vaccination was statistically insignificant but whether at earlier age TST+ reflects most probably the degree of exposure to TB cases than BCG vaccination should be clarified in the future.