LOS ANGELES, Calif. — Autism cases in California climbed even after a mercury-based vaccine preservative that some people blame for the neurological disorder was removed from routine childhood shots, a new study found.

Researchers from the state Department of Public Health found the autism rate in children rose continuously during the 12-year study period between 1995 and 2007. The preservative thimerosal hasn’t been used in childhood vaccines since 2001 but is used in some flu shots.

Doctors say the latest study adds to existing evidence refuting a link between thimerosal exposure and autism risk and should reassure parents that the disorder is not caused by vaccinations. If there was a risk, they said, autism rates should have dropped between 2004 and 2007.

For their study, California public health officials calculated the autism rate by analyzing a database of state-funded centers that care for people with autism and other developmental disorders. They found the prevalence of autism in children aged three to 12 increased throughout the study period; similar trends were found in other age groups.

Results were published in January’s issue of the journal Archives of General Psychiatry.

Federal statistics show about one in 150 children in the United States have autism, higher than previous estimates. Autism is characterized by impaired social interaction and communication skills.