Autism is usually diagnosed in children by age 3. Often, a diagnosis of autism, which is made based on observation of symptoms, not on a medical test, coincides with a child’s having recently received routine childhood vaccinations. Therefore, speculation about the connection between vaccines and autism persists. Particularly pervasive is the idea that vaccines that contain mercury can induce autism.
Dr. Martin Myers, director of the National Network for Immunization Information and a pediatrics professor at the University of Texas at Galveston, explains that “This myth was originally created by a couple of mothers of autistic children who read about methyl mercury poisoning and thought it sounded like autism.”
Methyl mercury is different from ethyl mercury, or thimerosal, which, until 2002, had been used to preserve vaccines. Today, the only common immunizations that contain thimerosal are Fluzone and Fluvirin, which also come in versions without thimerosal.
Thimerosal has been replaced by alternative preservatives; single-dose vaccines are also used, eliminating the need for preservatives. One version of the diphtheria-pertussis-tetanus (DPT) vaccine has a trace of thimerosal.
Although myths to the contrary persist, no evidence has been found that links ethyl mercury in vaccines to autism.
Research conducted by the Institute for Vaccine Safety at the Johns Hopkins Bloomberg School of Public Health in Baltimore shows that thimerosal is excreted from children’s bodies far faster than is methyl mercury. Dr. Neal Halsey, director of the Institute, states that the investigation of thimerosal in vaccines in 1990s came about not because of a concern about autism, but the concern that, “if by chance children got multiple thimerosal-containing vaccines, they might have enough mercury exposure that it might exceed the EPA guidelines.”
Dr. Halsey explains that the association between vaccines and autism, while incorrect, is understandable because symptoms may begin around the time of vaccinations.
Halsey states that organizations such as Autism Speaks are “not explaining that there will be coincidental timing of people recognizing the early signs of autism at the same time vaccines are given, so it’s an impossible task to try to keep doing research that addresses concerns that parents raise about bad things that are temporally associated with autism.”
The bottom line is that, while methyl mercury (such as that found in some fish and in now-recalled antiseptics Mercurochrome and Merthiolate) may cause problems in children in high doses, there is no causal connection between vaccines and autism.
For more information, see this article from the Pittsburgh Post-Gazette. Find mercury content of vaccines here.
