Vaccination associated thrombocytopenic purpura in children.

Patients who presented with purpura and blood platelets <30x10(9)/l within 1 month after vaccination were collected from a population based material of 506 consecutive pediatric patients with newly diagnosed ITP. Of the 35 such patients, 24 had thrombocytopenia after MMR vaccination giving an estimated ITP risk of approximately 1 in 30,000 MMR inoculations. Symptoms of the 35 patients were nearly always acute. Thrombocytopenia disappeared within a month in 74% of the study patients and lasted longer than 6 months in only 10%. Bleeding episodes were uncommon during the follow-up period. We conclude that the incidence of symptomatic thrombocytopenia after vaccinations is much lower than that after respective natural infections and that the outcome in most cases is excellent.