Although the cause of immune thrombocytopenic purpura (ITP) is often unknown, viral infection has been associated with ITP,1 especially in young children. Several studies have also reported an elevated risk of ITP after the first dose of a measles containing vaccine (MCV).2–6 Whether ITP recurs after the second MCV dose among children who developed ITP after the first MCV dose has not been examined in a population-based study.
In this study, which followed nearly one million children after 2 doses of a MCV, we found that none of the children who had ITP after the first dose developed ITP after the second dose. ITP incidence after the second dose (1 per 100 000 children) was much lower than the incidence after the first dose (5.4 per 100 000 children).