Federal health officials called a press conference last month to try to restore public confidence in childhood vaccines despite the charge by some parents that there is a connection between the vaccines and autism.
Several autism advocacy groups rallied on Capitol Hill last month to protest the use of mercury-containing thimerosal in vaccines.
But CDC director Julie Gerberding, M.D., said the predominance of evidence doesn't show an association between thimerosal in vaccines and autism.
Thimerosal has been used in vaccines as a preservative. However, since 2001 all vaccines recommended for children age 6 years and younger have either had no thimerosal or have contained only trace amounts.
One exception is the inactivated influenza vaccine. However, a preservative-free version, which contains trace amounts of thimerosal, is available in limited supplies. FDA officials are working with vaccine manufacturers to increase the supply of those doses, said Murray M. Lumpkin, M.D., acting deputy commissioner for international and special programs at the Food and Drug Administration.
In addition, all new vaccines licensed since 1999 are free of thimerosal as a preservative. Dr. Lumpkin said.
Dr. Gerberding said government researchers will continue to look at whether the evidence supports a link between thimerosal and autism but said it's important for researchers, policy makers, and parents not to base decisions on “unproved hypotheses.”
“Today the best available science indicates to us that vaccines save lives,” she said.
Researchers are trying to get an estimate of the prevalence of autism in children, and Dr. Gerberding said some of that data will be available next year.
In addition, researchers with the National Institutes of Health are investigating the risk factors and biological markers for autism.
“We need a war on autism, not a war on childhood vaccines,” said Peter Hotez, M.D., chair of the department of microbiology and tropical medicine at George Washington University, Washington, and the father of an autistic child.
Dr. Hotez said he is confident that vaccines have nothing to do with his daughter's autism, and if he could turn back time he would still give his daughter the full complement of vaccines. Instead, he said that parents should be reminded of the consequences of not vaccinating their children. And attention should shift from unfounded claims about vaccines to the need for respite care and other services for families with autistic children. Dr. Hotez also called for more research into the cause of autism and genetic testing for the disease.