Effect of neonatal bacille Calmette-Guérin on the tuberculin skin test reaction in the first 2 years of life

Setting Latent tuberculous infection (LTBI) is an important reservoir of disease reactivation that is sufficient to generate new cases for decades. The tuberculin skin test (TST) is an important tool to diagnose LTBI; however, neonatal bacille Calmette-Guérin (BCG) vaccination may impact interpretation of TST data. Objectives To analyse the effect of the neonatal BCG vaccine on TST reaction in the first 2 years of life in children with no identified contact with tuberculosis (TB). Design This was a cross-sectional study in children up to 2 years of age who received neonatal BCG vaccination. In the absence of baseline comorbidities or contact with the bacillus, the children were given the TST. Results Seventy-nine children participated in the study. A decline in TST reactivity was observed in the first 12-24 months of age in patients who had been vaccinated with neonatal BCG but with no contact with TB. After the age of 10 months, no patient showed a TST reaction of >5 mm. Conclusion BCG had low impact on the TST in children with no TB contact. This finding suggests the need to reassess the cut-off point to 5 mm of induration to improve TST specificity in LTBI identification.