The U.S. Centers for Disease Control and Prevention is planning a large study into potential connections between vaccines and autism, two sources familiar with the matter told Reuters, despite extensive scientific research that has disproven or failed to find evidence of such links.

The number of autism diagnoses in the United States has increased over the years. According to CDC data, about 1 in 36 children have been diagnosed with autism, compared to 1 in 150 in the year 2000.