Thrombocytopenia after immunization of Canadian children, 1992 to 2001.
BACKGROUND
Thrombocytopenia occasionally follows immunization of children, especially after administration of measles-containing vaccines. The purpose of this study was to describe the clinical features of postimmunization thrombocytopenia, with emphasis on the rate of complications and outcome.


METHODS
A prospective survey was conducted by 12 pediatric centers in Canada during 1992 to 2001. At each center a nurse monitor searched for inpatient cases. Cases were defined as having onset of clinical signs or laboratory measures of thrombocytopenia (platelet count, <50 x 10(9)/l) within 30 days after immunization. Cases were described in a standardized manner, including follow-up data as available.


RESULTS
Sixty-one cases were detected, an average of 6 per year or approximately 1 case per 15,000 general hospital admissions. Median age of cases was 13 months. The mean platelet count at diagnosis was 8.6 x 10(9)/l. Most cases (79%) followed measles-containing vaccines. Only 1 child had a serious (fatal) complication. Platelet counts returned to normal within 30 days of onset in 46 of 57 children (80.7%) with information available. Five children (8.2%) had persistent or intermittent thrombocytopenia for 3 months or more.


CONCLUSIONS
Thrombocytopenia associated with routine immunization of children is rare and usually benign, resolving within 1 month in most children.
Jadavji
Taj
T
Alberta Children's Hospital, Calgary.
Scheifele
David
D
Halperin
Scott
S
D017677:Age Distribution; D002170:Canada / Q000453:epidemiology; D002675:Child, Preschool; D003131:Combined Modality Therapy; D003625:Data Collection; D015721:Diphtheria-Tetanus-Pertussis Vaccine / Q000008:administration & dosage / Q000009:adverse effects*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007114:Immunization / Q000009:adverse effects* / Q000379:methods; D015994:Incidence; D007223:Infant; D008297:Male; D008458:Measles Vaccine / Q000008:administration & dosage / Q000009:adverse effects*; D022542:Measles-Mumps-Rubella Vaccine / Q000008:administration & dosage / Q000009:adverse effects*; D011446:Prospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D017678:Sex Distribution; D013921:Thrombocytopenia / Q000453:epidemiology* / Q000209:etiology* / Q000628:therapy
D015721:Diphtheria-Tetanus-Pertussis Vaccine; D008458:Measles Vaccine; D022542:Measles-Mumps-Rubella Vaccine