Risk factors for invasive pneumococcal disease in children: A population-based case-control study in North America

Objective. To identify risk factors for invasive pneumococcal disease, incl uding penicillin-resistant infections, among children 2 to 59 months of age . Design. Case-control study. Participants. Patients with invasive pneumococcal infections identified by population-based surveillance (n = 187) and controls identified through ran dom-digit telephone dialing (n = 280). Outcome measures. Invasive pneumococcal disease was defined as isolation of Streptococcus pneumoniae from a normally sterile site. Patients 2 to 59 mo nths of age who were residents of one of four active surveillance areas wer e included. S pneumoniae isolates were tested by broth microdilution. Isola tes with a minimum inhibitory concentration to penicillin greater than or e qual to 2 mu g/mL were considered resistant. Results. Invasive pneumococcal disease was strongly associated with underly ing disease and with day care attendance in the previous 3 months. Among 2- to 11-month-olds, current breastfeeding was associated with a decreased li kelihood of invasive pneumococcal disease (odds ratio, 0.27; 95% confidence interval: 0.08, 0.90). Penicillin-resistant infections were independently associated with day care attendance, at least one course of antibiotics, an d at least one ear infection in the previous 3 months. Conclusions. This study shows the association of underlying illnesses, day care attendance, and lack of breastfeeding with risk of invasive pneumococc al disease in children. The association of recent antibiotic use and infect ion with penicillin-resistant S pneumoniae highlights the need to avoid unn ecessary antibiotic use in children.