A report from a 2007 outbreak of tuberculosis among toddlers in Ireland found that 24% of the exposed children had received BCG immunization, and none of those vaccinated developed active infection.Based on absolute risk reduction, the number needed to treat (NNT) to prevent one case of active TB disease in their population is 11.3.
The results suggest effectiveness of BCG against all forms of TB in children rather than just the well known reduction in meningitis and invasive forms.
References:
BCG Vaccination Protects Toddlers Against Pulmonary Tuberculosis. Medscape.
Arch Dis Child 2009;94:392-393.
Xpert MTB/RIF is a rapid diagnostic test for tuberculosis with high sensitivity (90%) and specificity (99%). Lancet, 2011.
Image source: PPD, CDC, public domain.