Tuberculin sensitivity among children vaccinated with BCG under universal immunization programme.

A tuberculin survey was conducted among 45988 children with BCG scar and 54227 children without BCG scar between 1-9 years of age and residing in selected rural areas of three defined zones of India. About 45-60% of the BCG-vaccinated children elicited reactions < 5 mm in size and about 70-80% had reactions < 10 mm. Therefore, in the majority of children (showing tuberculin reaction of < 10 mm), BCG-induced tuberculin sensitivity does not interfere with interpretation of tuberculin test. The study also revealed that a proportion of reactions among BCG vaccinated children in 5-9 mm, 10-14 mm and 15-19 mm range may be attributable to BCG vaccination. Therefore, reactions between 10-14 mm and especially 15-19 mm among the vaccinated children must be interpreted carefully. However, 19 mm was observed as the upper limit for BCG induced tuberculin sensitivity and all reactions >- 20 mm in size may be considered to be due to infection with tubercle bacilli, irrespective of the BCG vaccination status.