title: A new approach to the definition of seroconversion following vaccination in a population with high background antibody concentrations.
abstract: Licensure of meningitis vaccines is increasingly being made on the basis of safety and immunogenicity. For meningococcal vaccines, a measure of immunogenicity is seroconversion, usually defined as a four-fold increase in rSBA titre. However, this definition is likely to underestimate seroconversion in settings with high background immunity. Using data from a study of the immunogenicity of meningococcal polysaccharide vaccines undertaken in Ghana, a logistic regression model to estimate the probability of seroconversion as a function of pre-vaccination titre has been developed. The seroconversion rate (91%) based on a variable-fold increase in rSBA titre derived from the model was a more plausible estimate of immunogenicity than the seroconversion rate (32%) based on the fixed four-fold increase in rSBA.
authors.affiliation: London School of Hygiene & Tropical Medicine, Keppel Street, London WC1E 7HT, United Kingdom. Daniel.chandramohan@lshtm.ac.uk
authors.forename: Daniel
authors.initials: D
authors.lastname: Chandramohan
authors.forename: Paul
authors.initials: P
authors.lastname: Coleman
authors.forename: Chris
authors.initials: C
authors.lastname: Nelson
authors.forename: Brian
authors.initials: B
authors.lastname: Greenwood
mesh_terms: D000907:Antibodies, Bacterial / Q000097:blood* / Q000276:immunology; D005869:Ghana; D006801:Humans; D016015:Logistic Models; D008585:Meningitis, Meningococcal / Q000276:immunology / Q000517:prevention & control; D022401:Meningococcal Vaccines / Q000008:administration & dosage / Q000276:immunology*; D015203:Reproducibility of Results; D014611:Vaccination / Q000379:methods / Q000592:standards
chemical_list: D000907:Antibodies, Bacterial; D022401:Meningococcal Vaccines