O'Leary ST, Glanz JM, McClure DL, Akhtar A, Daley MF, Nakasato C, Baxter R, Davis RL, Izurieta HS, Lieu TA, Ball R. Pediatrics. 2012 Feb;129(2):248-55. Epub 2012 Jan 9.
From the results of this study, ITP events seem unlikely after early childhood vaccines other than MMR. Because of the small number of exposed cases and potential confounding, the possible association of ITP with hepatitis A, varicella, and DTaP vaccines in older children requires further investigation. On the other hand, it is particularly interesting that in the 12- to 19-month age group, when ITP is relatively common, no increased risk of ITP for varicella, hepatitis A, DTaP, inactivated poliovirus, Haemophilus influenza type b, or pneumococcal conjugate vaccines was found.
The finding that the incidence risk ratio for MMRV does not appear to be elevated beyond that of MMR is also reassuring, given the recently reported two-fold increased risk of febrile seizures for MMRV compared with MMR and varicella vaccine given separately.