Evolving epidemiology of invasive Haemophilus infections in the post-vaccination era: results from a long-term population-based study.

Historically, Haemophilus influenzae (Hi) serotype b (Hib) caused most invasive Haemophilus infections worldwide, mainly in children. In 1989 routine childhood vaccination against Hib was initiated in Iceland. We conducted a population-based study of all patients in the country with Haemophilus spp....

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Bibliographic Details
Published in:Clinical Microbiology and Infection
Main Authors: Berndsen, M R, Erlendsdóttir, H, Gottfredsson, M
Other Authors: Faculty of Medicine, University of Iceland, Reykjavik, Iceland.
Format: Article in Journal/Newspaper
Language:English
Published: 2013
Subjects:
Adolescent
Adult
Aged
Child
Preschool
Haemophilus Infections
Haemophilus Vaccines
Haemophilus influenzae
Humans
Iceland
Incidence
Infant
Mass Vaccination
Meningitis
Haemophilus
Middle Aged
Pneumonia
Bacterial
Retrospective Studies
Risk Factors
Online Access:http://hdl.handle.net/2336/295201
https://doi.org/10.1111/j.1469-0691.2011.03700.x
Description
Summary:Historically, Haemophilus influenzae (Hi) serotype b (Hib) caused most invasive Haemophilus infections worldwide, mainly in children. In 1989 routine childhood vaccination against Hib was initiated in Iceland. We conducted a population-based study of all patients in the country with Haemophilus spp. isolated from sterile sites (n = 202), from 1983 to 2008. Epidemiology, clinical characteristics of the infections and serotypes of the isolates were compared during the pre-vaccination (1983-1989) and post-vaccination era (1990-2008). Following the vaccination, the overall incidence of Hib decreased from 6.4 to 0.3/100,000 per year (p <0.05) whereas the incidence did not change significantly for infections caused by Haemophilus sensu lato not serotype b, hereafter referred to as non-type b Hi (0.9 vs 1.2, respectively). The most frequent diagnosis prior to 1990 was meningitis caused by Hib, which was subsequently replaced by pneumonia and bacteraemia caused by non-type b Hi. Most commonly, non-type b Hi were non-typeable (NTHi; 40/59), followed by Hi serotype f (14/59) and Hi serotype a (3/59). Pregnancy was associated with a markedly increased susceptibility to invasive Haemophilus infections (RR 25.7; 95% CI 8.0-95.9, p <0.0001) compared with non-pregnant women. The case fatality rate for Hib was 2.4% but 14% for non-type b Hi, highest at the extremes of age. Hib vaccination gives young children excellent protection and decreases incidence in the elderly due to herd effect in the community. Replacement with other species or serotypes has not been noted. Pregnant women are an overlooked risk group.

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