OBJECTIVE: To determine the incidence of immune thrombocytopenic purpura (ITP) after measles-mumps-rubella (MMR) immunization compared with natural measles and rubella, its clinical course and outcome, and the risk of recurrence after repeat MMR vaccination.STUDY DESIGN: We performed a systematic review of the Ovid MEDLINE (1950 to present) bibliographic database. We selected studies that reported cases of thrombocytopenia in a known number of children who were immunized with MMR vaccine before development of ITP. We also extracted data from the same and other studies regarding bleeding manifestations and the resolution of MMR-associated thrombocytopenia or thrombocytopenic purpura within 6 months. Finally, we studied the risk of ITP recurrence after MMR immunization or reimmunization.RESULTS: On the basis of 12 studies, the incidence of MMR-associated ITP ranged from 0.087 to 4 (median 2.6) cases per 100,000 vaccine doses. Severe bleeding manifestations were rare, and MMR-associated thrombocytopenia resolved within 6 months from diagnosis in 93% of the children. MMR vaccination of unimmunized patients with ITP and revaccination of patients with prior ITP did not lead to recurrence of thrombocytopenia.CONCLUSIONS: MMR-associated ITP is rare, self-limited, and non-life threatening, and susceptible children with ITP should be immunized with MMR at the recommended ages.