The impact of a change in bacille Calmette-Guerin vaccine policy on tuberculosis incidence in children in Cape Town, South Africa

Background: A decision by the South African National Department of Health to change the route of administration and strain of bacille Calmette-Guerin (BCG) vaccine was implemented in Cape Town, South Africa, between July and December 2000. This provided an opportunity to compare the incidence of tuberculosis and proportion with disseminated disease in children less than 2 years old before and after the changeover from percutaneous (PC) Tokyo 172 BCG to intradermal (ID) 1331 Danish BCG immunization. Methods: Clinical records of all tuberculosis patients aged less than 2 years at diagnosis and born between January 1, 1999, and June 30, 2000 (PC cohort) and between January 1, 2001, and June 30, 2002 (ID cohort) were collected. All cases were reviewed for likelihood of TB, its severity and disease dissemination. Results: The number of reported patients with tuberculosis in the PC cohort was 1369 and in the ID cohort 1397, giving incidence rates of 866 (95% confidence interval [CI], 821-913) and 858 (95% CI, 814-904) per 100,000 person-years, respectively. The proportion who had disseminated disease (meningitis and/or miliary spread) was significantly lower in the ID cohort (4.7%) than in the PC cohort (8.6%) (relative risk, 0.54; 95% CI, 0.40-0.72). Those not vaccinated had a significantly higher proportion of disseminated disease cases (29.2%) than the PC and ID groups combined (6.6%) (relative risk, 4.4; 95% CI, 2.7-6.7). Conclusion: A program using Danish 1331 BCG given intradermally did not prevent more tuberculosis cases in children overall as compared with a program using Tokyo 172 BCG given percutaneously but reduced the proportion with disseminated disease.