Can BCG-vaccinated children be included in tuberculin surveys to estimate the annual risk of tuberculous infection in India?

SETTING

Selected villages in three defined zones of India.

OBJECTIVES

To compare the estimated prevalence of tuberculous infection among children with and without bacille Calmette-Guérin (BCG) scar.

STUDY

DESIGN

During a nationwide tuberculin survey, 1-9-year-old children were tuberculin tested using 1TU-PPD RT23 with Tween 80.

RESULTS

In the 5-9 year age group, subgroups of tuberculous infected children could be seen as distinct humps among those with or without BCG scar, but not in those aged 1-4 years. In children aged 1-4 years, the estimated prevalence of infection was respectively 3.5%, 3.8% and 3.6% among children without BCG scar, and 4.8%, 4.7% and 4.5% among children with BCG scar in the western, northern and eastern zones. In those aged 5-9 years, the estimated prevalence was respectively 10.4%, 11.0% and 9.1% among children without BCG scar and 11%, 11.9% and 8.7% among children with BCG scar in the three zones. Thus, in children aged 1-4 years, the estimated prevalence among those with BCG scar was considerably higher than in those without BCG scar. This difference was small in those aged 5-9 years.

CONCLUSION

Tuberculin surveys may be conducted irrespective of BCG scar status among children aged 5-9 years, when BCG vaccination is given using Danish 1331 strain during infancy under the Expanded Program of Immunization.