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Risk for immune thrombocytopenic purpura associated with MMR vaccine, no link to other vaccines
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There was a significant association between immune thrombocytopenic purpura and the measles-mumps-rubella vaccine, researchers reported during a presentation.
In this Kaiser Permanente-sponsored retrospective cohort study of 1.8 million children aged 2 months to 17 years, Sean O’Leary, MD, a pediatric infectious disease specialist at the University of Colorado, Denver, and colleagues analyzed data collected from five managed care organizations between 2000 and 2009 to identify cases of immune thrombocytopenic purpura (ITP). All potential cases were identified by ICD-9 codes and platelet counts of less than 50,000/mcL. Incidence rate ratios were calculated using the self-controlled case series method, with a 1- to 42-day risk window within discrete age categories, and were figured using for routine childhood and adolescent vaccines. All cases were verified by chart review.
Researchers found that of the 15 million vaccines administered to the children in the analysis, there were 197 chart-confirmed ITP cases, most of which were acute and mild, with no lasting adverse effects. The incidence rate ratio for the first dose of the MMR vaccine administered to those aged 12 to 19 months was greatly elevated (6.99; 95% CI, 1.56-31.22).
Elevated incidence rate ratios also occurred with the hepatitis A (Hep A) vaccine administered to those aged 7 to 17 years (18.33; 95% CI, 2.23-150.51); and varicella-zoster (14.07; 95% CI, 1.13-174.57) and tetanus-diphtheria-acellular pertussis vaccine (19.1; 95% CI, 3.02-121.49) given to those aged 11 to 17 years. For Hep A, VZV and Tdap, elevated incidence rate ratios were calculated on one to two vaccine-exposed cases.
Noting that the study confirmed prior findings published in a 2008 issue of Pediatrics, O’Leary told Infectious Diseases in Children in an email that, “The important new findings from this study are that the other vaccines in early childhood are likely not associated with ITP, at a time when ITP is most common, and that there may be an association of ITP with certain vaccines in older children. If so, it is very rare and not severe. These findings were based on one to two cases in the 42-day exposure window.”
For more information:
- O’Leary S. #25334.
Disclosure: Dr. Leary reports no relevant financial disclosures to report.