RISK-FACTORS FOR PRIMARY INVASIVE PNEUMOCOCCAL DISEASE AMONG CHILDREN IN FINLAND

Objective.-To study risk factors for invasive pneumococcal disease among children. Design.-A population-based, case-control study of 149 cases and 284 controls matched for age, sex, and place of residence. Setting.-Finland, November 1986 through November 1989. Patients and Controls.-Patients were identified from a prospective nationwide surveillance for invasive bacterial diseases among children (0 to 15 years of age) through a network of bacteriologic laboratories. Two matched controls were selected for 135 of the cases and one matched control for 14 of the cases from the respective cases' child health center or school. Questionnaires evaluating potential risk factors were mailed to families of cases and controls. Results.-An increased risk for invasive pneumococcal disease among children younger than 2 years was associated with day care center attendance (odds ratio [OR]=36; 95% confidence interval [CI], 5.7 to 233), family day care (OR=4.4; 95% CI, 1.7 to 12), and history of frequent otitis media (OR=8.8; 95% CI, 2.5 to 31). For those at least 2 years of age, existence of siblings younger than school-age indicated increased risk for invasive pneumococcal disease (OR=2.2; 95% CI, 1.1 to 4.4). Conclusions.-Day care center attendance is a major risk factor for invasive pneumococcal disease for children younger than 2 years, with significantly higher risk than the risk associated with family day care.