BCG revaccination and tuberculin reactivity

Interpretation of tuberculin reactions in revaccinated children is somewhat controversial among paediatricians. In this study, the effect of the number of BCG vaccines on tuberculin reactivity is evaluated. In 2810 healthy children aged 7 to 14 years with purified protein derivative (PPD) testing. Children were grouped according to the concordance of the number of the reported/documented vaccinations to the number of scars. Group 1 and 2 comprised of children 7 to 10 years of age and 11 to 14 years of age respectively, who had non-concordant scar numbers, and Group 3 and 4 included 7 to 10 and 11 to 14 years old children with concordant scar numbers. Mean tuberculin induration sizes were 8.0 +/- 5.7 mm for Group 1, 10.6 +/- 4.9 mm for Group 2, 9.8 +/- 4.9 mm for Group 3 and 10.9 +/- 4 mm for Group 4. As the time interval after the last dose of vaccination increased, mean induration sizes decreased in Group 1 and Group 3. In contrast, the mean reaction sizes of Group 2 and Group 4 showed a positive correlation with the period after the last dose of vaccine. It seems advisable that an induration size > or = 15 mm should not be attributed to BCG vaccination in countries with a high tuberculosis infection prevalence and routine BCG revaccination policies. A detailed investigation for tuberculosis infection and disease should be performed in those cases.