Epidemiological evaluation of BCG vaccine efficacy in Delhi--1989

A field evaluation of efficacy of BCG vaccine to prevent tubercular meningitis was undertaken in a case control study in Delhi during 1988-89. Each case of tubercular meningitis was matched by age and neighbourhood with 2 controls from the community. Thirty-seven cases of tubercular meningitis were matched with 74 controls and thus 37 triplets were analysed. ODDS RATIO between BCG vaccinated and non vaccinated individuals for acquisition of tubercular meningitis was 11.3. This gives 84 per cent efficacy of BCG vaccine in the prevention of TB meningitis under the field conditions prevailing in Delhi. Paired matched analysis of tubercular meningitis with the control group 1 and 2 separately revealed the ODDS RATIO to be 9.5 and 15 respectively. The corresponding BCG vaccine efficacy worked out were 90 and 93 per cent respectively. Authors suggest that this method of evaluating BCG vaccine efficacy is fairly reliable and cost effective. This methodology could be further simplified by using hospital patients as control and be introduced to evaluate BCG vaccine efficacy in different areas with reference to its role in preventing tubercular meningitis under the programme of immunisation.