title: Risk of immune thrombocytopenic purpura after measles-mumps-rubella immunization in children.
abstract: BACKGROUND
  The measles-mumps-rubella vaccine has been associated with immune thrombocytopenia purpura in 2 small studies.
  
  
  METHODS
  By using the Vaccine Safety Datalink, we identified measles-mumps-rubella-vaccinated children aged 1 to 18. A case of immune thrombocytopenia purpura was defined as a patient with a platelet count of < or = 50,000/microL with clinical bleeding and normal red and white blood cell indices. The immune thrombocytopenia purpura incidence rates during exposed (42 days after vaccination) and unexposed time periods were determined. A retrospective cohort of vaccinated children was used to determine incident rate ratios for children aged 1 to 18 years, 12 to 23 months, and 12 to 15 months.
  
  
  RESULTS
  A total of 1,036,689 children received 1,107,814 measles-mumps-rubella vaccinations; there were 259 confirmed patients with immune thrombocytopenia purpura. Because only 5 exposed cases occurred after age 2, analyses were limited to children aged 12 to 23 months. Exposed patients aged 12 to 23 months had lower median platelet counts than those who were unexposed and had similar median duration of illness (11 vs 10 days). The incident rate ratio was highest for children aged 12 to 15 months at 7.10. The incident rate ratio for boys aged 12 to 15 months was 14.59, and the incident rate ratio for girls in the same age group was 3.22. Seventy-six percent of immune thrombocytopenia purpura cases in children aged 12 to 23 months were attributable to measles-mumps-rubella vaccination. This vaccine causes 1 case of immune thrombocytopenia purpura per every 40,000 doses.
  
  
  CONCLUSIONS
  Measles-mumps-rubella vaccine that is given in the second year of life is associated with an increased risk of immune thrombocytopenia purpura.
authors.affiliation: Department of Preventive Medicine, Kaiser Pemanente Colorado, Denver, CO 80231, USA. eric.k.france@kp.org
authors.forename: Eric K
authors.initials: EK
authors.lastname: France
authors.forename: Jason
authors.initials: J
authors.lastname: Glanz
authors.forename: Stanley
authors.initials: S
authors.lastname: Xu
authors.forename: Simon
authors.initials: S
authors.lastname: Hambidge
authors.forename: Kristi
authors.initials: K
authors.lastname: Yamasaki
authors.forename: Steve B
authors.initials: SB
authors.lastname: Black
authors.forename: Michael
authors.initials: M
authors.lastname: Marcy
authors.forename: John P
authors.initials: JP
authors.lastname: Mullooly
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Jackson
authors.forename: James
authors.initials: J
authors.lastname: Nordin
authors.forename: Edward A
authors.initials: EA
authors.lastname: Belongia
authors.forename: K
authors.initials: K
authors.lastname: Hohman
authors.forename: Robert T
authors.initials: RT
authors.lastname: Chen
authors.forename: Robert
authors.initials: R
authors.lastname: Davis
mesh_terms: D000293:Adolescent; D017677:Age Distribution; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007115:Immunization Schedule; D015994:Incidence; D008297:Male; D022542:Measles-Mumps-Rubella Vaccine / Q000008:administration & dosage / Q000009:adverse effects*; D016012:Poisson Distribution; D011696:Purpura, Thrombocytopenic / Q000453:epidemiology* / Q000209:etiology / Q000276:immunology*; D012042:Registries; D012189:Retrospective Studies; D018570:Risk Assessment; D012720:Severity of Illness Index; D017678:Sex Distribution; D014481:United States
chemical_list: D022542:Measles-Mumps-Rubella Vaccine