Does B.C.G. vaccination prevent or postpone the occurrence of tuberculous meningitis?

The reported efficiency of B.C.G. vaccine in prevention of primary childhood or sputum positive adult tuberculosis vary widely but it is believed to offer significant protection against hematogenous forms of tuberculosis. The present hospital-based, case control study was aimed at evaluation of impact of B.C.G. vaccination on one of the hematogenous forms of tuberculosis i.e. Tuberculous meningitis (TBM). Records of cases of TBM admitted in the pediatric wards of Lok Nayak Hospital, Delhi, over one year were analyzed retrospectively for B.C.G. positivity status and age distribution. The results were compared with similar data obtained from a control group comprising of non-TBM cases in pediatric wards of same hospital, recruited on 2 days, separated by an interval of three weeks. No statistically significant difference was found in B.C.G. positivity status of cases and control groups. However, there was an obvious trend in age distribution among cases of TBM with respect to the B.C.G. status, with a significantly higher proportion of B.C.G. vaccinated children in over 5-year age group, as compared to those in under 5 year age group. The results, therefore, indicate probable effectiveness of B.C.G. against TBM only for a limited duration i.e. single B.C.G. immunization only postpones rather than prevent the occurrence of TBM.