Invasive Haemophilus influenzae disease: An ecological study of sociodemographic risk factors before and after the introduction of Hib conjugate vaccine

This study examines the impact of H. influenzae type b (Hib) conjugate vaccine on sociodemographic risk factors for invasive H. influenzae disease in the 2 years before and immediately after the introduction of Hib conjugate vaccine. An ecological study design was used and cases were identified using active surveillance employing several surveillance systems. The study population comprised all children aged