Final answer:
A study conducted in Japan showed no link between the MMR vaccine and regression in autism spectrum disorders.
Step-by-step explanation:
A study conducted in Japan investigated the association between the MMR vaccine and regression in autism spectrum disorders. The study, published in the Journal of Autism and Developmental Disorders, presented negative results, indicating that there was no link between the MMR vaccine and the onset of autism spectrum disorders. The study's findings countered the claim that the MMR vaccine causes autism, providing evidence that vaccines are safe and do not contribute to the development of autism spectrum disorders.