BCG vaccination is associated with decreased severity of tuberculosis in Pakistan

Vaccination with Bacille Calmette–Guérin (BCG) is given at birth to protect against tuberculosis (TB) in Pakistan. The country ranks 6th amongst high-burden countries worldwide and has an incidence of 231/100,000 pyopulation. This was a cross-sectional multi-center hospital-based study. TB patients (n = 218) with pulmonary (PTB, n = 120) or extrapulmonary (ETB, 98) were recruited, and the presence of a BCG vaccination scar was documented. Cases were further classified into minimal, moderate and advanced PTB or less severe (L-ETB) or severe disseminated (D-ETB) disease. The association of age, gender and severity of TB infections with BCG vaccination of the individual TB cases was investigated. No difference was found of the BCG vaccination status of PTB and ETB cases, or in relation to age or gender. Patients under 29 years of age comprised the largest group. There were more females with ETB than PTB. The largest group within ETB comprised those with tuberculous lymphadenitis (LNTB, 39%). A significantly greater number of LNTB cases had received BCG vaccinations than had those with pleural (unilateral) TB (p = 0.004), and tuberculous meningitis (p = 0.027) groups. Also, there were more immunized patients with pulmonary as compared with pleural disease (p = 0.001). LNTB represents localized granulomatous disease and the observation of higher vaccination rates in this group suggests that BCG has protected against more severe forms of TB in this high-burden region