Atypical mycobacteria in extrapulmonary disease among children: Incidence in Sweden from 1969 to 1990, related to changing BCG-vaccination coverage

Summary Setting: In April 1975, the general BCG vaccination of newborns in Sweden was replaced by selective vaccination of groups at increased risk for tuberculosis. Objective: To relate the incidence of atypical mycobacterial disease in children to BCG vaccination. Design: A nationwide survey in Sweden during the period 1969–90 disclosed 390 children under 15 years of age with bacteriologically confirmed atypical mycobacteria from extrapulmonary lesions. Results: The average, annual incidence of atypical mycobacterial disease per 100 000 children under 5 years of age increased from 0.06 during the period 1969–74 to a maximum level of 5.7 during 1981–85. Among the cohorts born in Sweden in the period 1975–85, the cumulative incidence rate before 5 years of age was estimated at 26.8 per 100 000 non-BCG-vaccinated children and at 4.6 among those BCG-vaccinated, ratio 5.9 (95% confidence limits 1.6, 48.5). Mycobacterium avium-intracellulare was found in 83%. Disseminated, fatal disease developed in 3 children. The remaining ones suffered from local infections, most often lymphnode or soft-tissue lesions. The observed incidence of bacteriologically confirmed diagnosis was estimated to represent approximately 40% of the ‘true’ number, if patients with diagnosis based on histological, clinical and epidemiological findings only were included. Conclusion: The present study indicates that BCG vaccination plays a role in protection against localized disease caused by atypical mycobacteria in children.