title: MMR vaccine and idiopathic thrombocytopaenic purpura.
abstract: OBJECTIVE
  To estimate the relationship between idiopathic thrombocytopaenic purpura (ITP) and the measles, mumps and rubella (MMR) vaccination in children; calculating the relative risk estimate for ITP with in 6 weeks after MMR vaccination and the attributable risk of ITP within 6 weeks after MMR vaccination.
  
  
  METHODS
  Using the General Practice Research Database we identified children with a first-time diagnosis of ITP from a base population of children aged less than 6 years between January 1988 and December 1999. After describing the characteristics of all the children identified with ITP, we focused on cases aged 13-24 months to perform a population-based, case-control analysis to estimate the relative risk of developing ITP within 6 weeks after MMR vaccination. We also calculated the risk of ITP attributable to the MMR vaccination.
  
  
  RESULTS
  Sixty-three children with a first time diagnosis of ITP were identified; 23 cases were between 13 and 24 months old. The relative risk estimate for ITP within 6 weeks after MMR vaccination, compared to the combined group of unvaccinated children and children vaccinated with MMR more than 26 weeks previously was 6.3 (95% CI 1.3-30.1). The attributable risk of developing ITP within 6 weeks after MMR vaccination was estimated to be 1 in 25,000 vaccinations (95% confidence interval 21,300, 89,400).
  
  
  CONCLUSIONS
  This study confirms the increased risk of ITP within 6 weeks after MMR vaccination. However, the attributable risk of ITP within 6 weeks after MMR vaccination is low.
authors.affiliation: Department of Public Health, Aberdeen University, Aberdeen, UK. corri.black@abdn.ac.uk
authors.forename: Corri
authors.initials: C
authors.lastname: Black
authors.forename: James A
authors.initials: JA
authors.lastname: Kaye
authors.forename: Hershel
authors.initials: H
authors.lastname: Jick
mesh_terms: D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D022542:Measles-Mumps-Rubella Vaccine / Q000009:adverse effects*; D016553:Purpura, Thrombocytopenic, Idiopathic / Q000209:etiology*; D012307:Risk Factors
chemical_list: D022542:Measles-Mumps-Rubella Vaccine