title: Haemophilus influenzae type b and cross-reactive antigens in natural Hib infection dynamics; modelling in two populations.
abstract: Natural immunity to Haemophilus influenzae type b (Hib) invasive disease is based on antibodies arising in response to encounters with Hib or cross-reactive (CR) bacteria. The relative importance of Hib and CR contacts is unknown. We applied a statistical model to estimate the total rate of immunizing infections of Hib and CR prior to wide-scale vaccinations in Finland and the UK. The average rates of these contacts were 0.7 and 1.2 per year per child in Finland and the UK, respectively. Using a rough estimate of 0.1 Hib acquisitions per year per child in the UK based on carriage rates, the proportion of Hib among all immunizing contacts was in the order of 10%, suggesting that CR bacteria have a major role. In general, varying frequency of CR contacts may explain some differences in the pre-vaccination incidence and age-distribution of invasive disease in different countries.
authors.affiliation: National Public Health Institute, Helsinki, Finland.
authors.forename: T
authors.initials: T
authors.lastname: Leino
authors.forename: K
authors.initials: K
authors.lastname: Auranen
authors.forename: P H
authors.initials: PH
authors.lastname: Mäkelä
authors.forename: H
authors.initials: H
authors.lastname: Käyhty
authors.forename: M
authors.initials: M
authors.lastname: Ramsay
authors.forename: M
authors.initials: M
authors.lastname: Slack
authors.forename: A K
authors.initials: AK
authors.lastname: Takala
mesh_terms: D000367:Age Factors; D000907:Antibodies, Bacterial / Q000097:blood; D000942:Antigens, Bacterial / Q000276:immunology*; D016667:Bacterial Capsules; D002648:Child; D002675:Child, Preschool; D003429:Cross Reactions; D005387:Finland / Q000453:epidemiology; D006192:Haemophilus Infections / Q000453:epidemiology* / Q000276:immunology; D018073:Haemophilus Vaccines / Q000276:immunology; D019741:Haemophilus influenzae type b / Q000276:immunology*; D006801:Humans; D007112:Immunity, Maternally-Acquired; D007114:Immunization; D007223:Infant; D007231:Infant, Newborn; D015233:Models, Statistical; D011135:Polysaccharides, Bacterial / Q000276:immunology; D006113:United Kingdom / Q000453:epidemiology
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D018073:Haemophilus Vaccines; C044237:Haemophilus influenzae type b polysaccharide vaccine; D011135:Polysaccharides, Bacterial