Neonatal BCG Vaccine and Response to the Tuberculin Test in BCG Vaccinated Children in Contact with Tuberculosis Patients in Recife, Brazil

This case-control study analyses the association between the tuberculin response and the neonatal BCG vaccine in 330 children under 15 who are home contacts of tuberculosis patients, taking into account risk factors for the transmission of infection. Interviews were conducted with 330 children, their parents or legal guardians. Chest X-rays were taken and the tuberculin test (TT) applied using 0.1 ml of PPD RT23, taking an induration reading of ≥10mm as the cut-off point for a positive test result. Prior BCG vaccination was ascertained by observing the presence of a scar on the deltoid region of the right arm. Six children were excluded because they had signs/symptoms of pulmonary tuberculosis, thereby reducing the final sample to 324 children. The multivariate analysis showed that being exposed to a patient with pulmonary lesions with cavities (OR = 3.14; CI: 1.59–6.20; p = 0.000), a positive sputum smear (OR = 3.65; CI: 1.52–8.78; p = 0.002) or a positive culture (OR = 4.42; CI: 1.39–14.1; p = 0.005), being under five (OR = 0.47; CI: 0.22–0.99; p = 0.045) are independently associated with a positive TT. The fact that a prior BCG scar is not associated with a positive response to the TT indicates the need to re-open discussion of the guidelines which exist in many poor countries where tuberculosis is still a serious public health problem. Such guidelines include those issued by the Brazilian Ministry of Health, which considers the child under 15 in contact with a tuberculosis case to be infected only if there is a TT of 10 mm or more and the child received no prior BCG vaccination.