The effect of bacille Calmette-Guerin vaccination at birth on tuberculin skin test reactivity in Ugandan children

Setting: In Uganda, bacille-Calmette Guerin (BCG) vaccination coverage at birth is between 82 and 84%. Objective: To evaluate the effect of neonatal BCG vaccination on tuberculin skin test positivity in Ugandan children exposed to infectious cases. Design: As part of an ongoing prevalence study of household contacts of new tuberculosis cases, 365 children were evaluated to determine if BCG vaccination at birth had an impact on tuberculin skin testing. The children were classified as contacts (179) and non-contacts (186) depending on the presence of a sputum acid-fast bacilli (AFB) smear-positive adult tuberculosis case in the household. Results: Regardless of prior BCG vaccination, children exposed to a smear-positive adult were more likely to have a positive skin test (purified protein derivative >5mm) (68% versus 36%, P <0.01). BCG-vaccinated children below 1 year of age without a known household contact with active tuberculosis had a lower frequency of tuberculin skin reactions (29%) compared to their counterparts in the contact households (65%, P = 0.031). Conclusion: BCG vaccination at birth had no important effect on the interpretation of the tuberculin skin test reactivity in this group of Ugandan children. The tuberculin skin test remains a valuable tool for the evaluation of household contacts and suspected cases of tuberculosis in BCG-vaccinated children.