Idiopathic thrombocytopenic purpura (ITP) is a relatively common hematological disease in children. It generally occurs after exposure to a common viral infection episode; however, it may occasionally follow immunization with measles, measles-mumps-rubella (MMR), hepatitis B (HBV), influenza, diphtheria-tetanus-pertussis (DTP), or chickenpox vaccines. In this study, the incidence, clinical characteristics, and treatment outcome of vaccination-associated ITP were investigated and compared with non-vaccination-associated ITP.

The admission records of 105 pediatric ITP patients between 0-14 years of age admitted to Department of Pediatrics, Wonkwang University Hospital from January 1994 to July 2007 were retrospecitively reviewed. Patients were grouped into a vaccination-associated group and a non-vaccination-associated group according to vaccination history within the previous 1 month, and various clinical features between the two groups were statistically analyzed.

Thirteen patients (12%) had a preceding vaccination. Eight had received DTP vaccination, 2 had received hepatitis B, and 1 each had received influenza, MMR, and Japanese B encephalitis vaccination. However, none of the patients had a recurrent thrombocytopenia after subsequent vaccinations. In the vaccination-associated group, the age was significantly lower, anemia was more common, and the risk period with blood platelet count <20×10⁹/L was significantly shorter than for the in non-vaccination-associated group. Also, wet purpura was less prominent and the remission within 1month was more frequently achieved in the vaccination-associated ITP group.

Vaccination-associated ITP patients showed mild symptoms with a more benign and shorter lasting course than non-vaccination-associated ITP patients. Moreover, platelet count assessment at the time of the next immunization may not be necessary.