Background: The introduction of a conjugate type b Haemophilus influenzae (Hib) vaccine for children has led to a sharp drop in the incidence of H. influenzae disease. The purpose of this study is that of analyzing the major characteristics of invasive disease due to H. influenzae as regards epidemiology, clinical aspects, evolution and immunization status among the infantile population of the Autonomous Community of Valencia for the 1996-2000 period.
Method: The data was taken from the clinical records of those children under age 15, who have shown clinical signs and symptoms indicative of invasive disease entailing isolation of Haemophilus influenzae and/or meeting the established case definition requirements, who were treated at all of the public hospitals in the Autonomous Community of Valencia throughout the 1996-2000 period. The trend of incidence was assessed by mean of incidence rates. The clinical pattern and the evolution there of (sequelae and life-threatening aspects) by frequency and age range.
Results: A total of 36 cases of invasive disease due to Haemophilus influenzae were recorded. The incidence rate among children under age 15 dropped from 3.56/10(5) in 1996 to 1.07/10(5) in 1997 (coinciding with the immunization campaign and the subsequent including of the conjugate Hib vaccine in the Routine Vaccination Schedule of the Autonomous Community of Valencia) and 0.30/10(5) in 1998, this being a situation which has continued over the following years. Fifty-three percent (53%) of the cases occur in children under age 18 months. Both the sequelae as well as the deaths occurred throughout the period prior to the routine use of the conjugate vaccine. No child properly immunized died. Two cases of non-b type H. influenzae occurred in immunized children.
Conclusions: The incidence of infection due to type b Haemophilus influenzae dropped drastically as of the start of the routine immunization of the infantile population.