Population-based study of the association between asthma and pneumococcal disease in children

Kimberly M Shea,1,2 Timothy L Lash,3,4 Sussie Antonsen,4 Susan S Jick,1,5 Henrik T Sørensen1,41Department of Epidemiology, Boston University School of Public Health, 2Department of Pediatrics, Boston University School of Medicine, Boston, MA, 3Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, GA, USA; 4Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark; 5Boston Collaborative Drug Surveillance Program, Boston University, Boston, MA, USABackground: Although asthma has recently been established as a risk factor for pneumococcal disease (PD), few studies have specifically evaluated this association in children.Methods: We conducted a nation-wide population-based cohort study of the effect of asthma on childhood PD among all singleton live births in Denmark from 1994 to 2007, before the introduction of the 7-valent pneumococcal conjugate vaccine. All data were abstracted from Danish medical registries. Because underlying comorbidity substantially increases the PD risk in children, standard methods were used to assess the evidence of biologic interaction between comorbidity and asthma on the risk of PD.Results: There were 2,253 cases of childhood PD among 888,655 children born in Denmark from 1994 to 2007. The adjusted incidence rate ratio of the effect of asthma on childhood PD was 2.2 (95% confidence interval [CI]: 2.0, 2.5). Age-stratified incidence rate ratios were 2.1 (95% CI: 1.8, 2.9) in children 6 months to