1. In this study of children with older siblings with or without an autism spectrum disorder (ASD), there was no increased risk of development of an autism spectrum disorder following receipt of the measles-mumps-rubella (MMR) vaccine regardless of their older sibling’s ASD status.
2. Among children with older siblings with an ASD, there was also no association detected between the number of MMR vaccine received (i.e., 1 versus 2 doses) and the risk of ASD development.
Evidence Rating Level: 2 (Good)
Study Rundown: While the association between vaccination and autism spectrum disorders (ASD) has been previously refuted in scientific studies, there remains a subset of individuals who continue to assert an association. Although the validity of this association may be particularly concerning to parents who already have one or more children with an autism spectrum disorder, there has only been one prior small study investigating this particular risk cohort. Consequently, the authors of this current study aimed to compare the risk of ASD following measles-mumps-rubella (MMR) vaccination in a large sample of children with older siblings who did and did not have an ASD.
In summary, this study found no association between MMR vaccination and ASD risk in children regardless of their older siblings’ ASD status. The study also found that the lack of association in children with older siblings with an ASD persisted regardless of the number of MMR vaccination doses the children received. While this study is strengthened by its large sample size, it is limited by the generalizability of its findings, as only privately insured patients were included. Nevertheless, the results of this study corroborated those of prior studies that have found no association between the risk of ASD development and MMR vaccination.
In-Depth [retrospective cohort study]: This study used a large private insurance database to assess 95 727 children who were continuously insured by the company from birth to 5 years of age and who also had an older sibling who was continuously insured by the company for at least 6 months. Number of MMR vaccination doses and age of receipt was recorded, as well as the presence or absence of an ASD in the older sibling. Of the 1929 children with an older sibling with an ASD, 6.9% (n = 134) were diagnosed with an ASD while in children with an older sibling without an ASD, 0.9% (n = 860) were diagnosed with an ASD (p < 0.001). The adjusted risk ratio for children who received 1 dose of the MMR vaccine who had an older sibling with ASD was 0.91 (95%CI 0.67-1.20; p = 0. 50) and was 0.76 (95%CI 0.49-1.18; p = 0.22) for children who had an older sibling without an ASD. The adjusted risk ratio for children who received 2 doses of the MMR vaccine who had an older sibling with ASD was 0.56 (95%CI 0.31-1.01; p = 0.052) and was 1.12 (95%CI 0.78-1.59; p = 0.55) for children who had an older sibling without an ASD.
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