Day care attendance and other risk factors for invasive Haemophilus influenzae type b disease

Two hundred and ninety-five of 373 (79%) children with reported cases of invasive Haemophilus influenzae type b (Hib) occurring in the state of Oklahoma from January 1, 1986, through December 31, 1987, were matched according to birth date with two controls each. Conditional logistic regression was used to assess the independent roles of day care attendance, number of young children in the home, crowding, passive smoking, maternal education, household income, and race in Hib disease. Statistically significant odds ratios (ORs) were found for day care attendance (OR = 2.9), the presence of two or more children in the home under 6 years of age (OR = 2.4), crowding (ratio of number of people in the home to number of bedrooms > or = 2) (OR = 2.0), and exposure to cigarette smoking in the home (OR = 1.4). Household income was independently associated with Hib disease. African Americans were at increased risk even after adjustment for income and crowding (OR = 4.1). Although there were no important differences in risk for other factors by type of Hib disease, there was a large and statistically significant difference in risk for day care attendance between meningitis (adjusted OR = 5.1, 95% confidence interval (CI) 3.1-8.2) and other types of Hib disease (combining nonmeningitis cases, adjusted OR = 1.6, 95% CI 0.9-2.7). Increasing numbers of hours per week of day care attendance and children per room were associated with increasing risk of Hib meningitis in a dose-response pattern. The highest day care ORs for meningitis were observed in the youngest (< 6 months) and oldest (> or = 24 months) children. The adjusted OR for exposure to breast feeding was 0.5 (95% CI 0.3-0.8). A protective effect for Hib polysaccharide vaccination among children aged > or = 18 months was suggested but did not reach statistical significance (OR = 0.4, 95% CI 0.2-1.1).