it 's too soon to determine whether autism rates have been affected . Do these findings suggest that autism is n't linked to mercury in vaccines ? Dr. Sanjay Gupta , chief medical correspondent : Let me explain . In 1999 , manufacturers began removing thimerosal - which is a mercury-based preservative - from vaccines . Some people believed autism would decrease as a result , because they thought the two were connected . A new study in the Archives of General Psychiatry says this just did n't happen . Researchers looked at cases of autism in California after 1999 . They reasoned that if mercury exposure in vaccines was a major cause of autism , the number of affected kids should have dropped after thimerosal was removed . Just the opposite happened . From 2004 to 2007 , when exposure to thimerosal dropped significantly for 3 - to 5-year-olds , the autism rate continued to go up , from 3 per 1,000 children to 4 per 1,000 children in California . A child psychiatrist who supported the study said it `` very clearly shows that autism did not arrive through a vaccine . '' But advocacy groups say it
One doctor says the study `` very clearly shows that autism did not arrive through a vaccine . '' A new study published in the January 2008 issue of Archives of General Psychiatry found the prevalence of autism cases in California children continued to rise after most vaccine manufacturers started to remove the mercury-based preservative thimerosal in 1999 , suggesting that the chemical was not a primary cause of the disorder . Researchers from the State Public Health Department found that the autism rates in children rose continuously during the study period from 1995 to 2007 . The preservative , thimerosal , has not been used in childhood vaccines since 2001 , except for some flu shots . The latest findings failed to convince some parents and advocacy groups , who have long blamed mercury , a neurotoxin , for the disorder . For years , parents have been concerned that a mercury-containing vaccine preservative may play a role in autism . But a study conducted in California found that autism rates increased even after thimerosal was removed from most vaccines . The study authors say this is evidence that thimerosal does not cause autism , although advocacy groups say