A CDC study concluded that the amount of antigens from vaccines received on one day of vaccination or in total during the first two years of life is not related to the development of autism spectrum disorder. The findings, published in The Journal of Pediatrics, should help to alleviate parents' concerns that "too many vaccines too soon" can lead to autism in their children. Researchers collected data from three managed care organizations and evaluated the total number of vaccine antigens -- which stimulate the body's immune system -- received in the first two years of life and on a single day in a group of 256 children with ASD compared to 752 children without ASD. The children were born between 1994 and 1999 and were age 6-13 when the data were collected. The researchers found no association between higher levels of vaccine antigen exposure and ASD. More than 1 in 10 parents of young children refuse or delay vaccinations, due largely to safety concerns, according to a recent survey. Read the study.