Are Vaccines Linked to Autism? The Facts Behind the Controversy
Vaccines Linked to Autism: The Claim
Do vaccinations cause autism? Some parents of autistic children, as well as some researchers, believe that they do. A number of parents came to this conclusion originally because they noticed that right after a vaccination, their children began to regress and lose some of the skills that they had already gained, such as speech and motor control. Opponents of this position posit that these parents drew the wrong conclusions. They believe that regressive autism only becomes apparent at about the same time that vaccinations are given, and that the fact that the two tend to happen at a similar stage of infancy is a coincidence.
Vaccines linked to autism in the past include the MMR (measles, mumps, and rubella) vaccine, as well as mercury found in many other vaccines.
The MMR Vaccine
The vaccine controversy really took off in 1998, when Dr. Andrew Wakefield published a study in a medical journal called The Lancet. His study suggested that the MMR vaccine could be a cause of autism and other similar developmental problems and that the vaccine could become lodged in the intestines and somehow affect the child’s brain. Twelve years later, in 2010, The Lancet retracted this paper, publicizing the fact that the study was flawed, and that its results could not be replicated. More than a dozen studies carried out since 1998 (involving more than a million children) have found no significant link between the MMR vaccine and autism.
During the scrutiny of the MMR vaccine, researchers also examined other vaccines to see whether they could be causing any harm to the children receiving them. They suspected that thimerosal; a mercury-based preservative used in many vaccines was dangerous.
In 1998, children who followed their pediatrician’s vaccination schedule were injected with thirty different vaccines that contained thimerosal, which exceeded the limit of mercury that the government of the U.S. found acceptable. Because mercury poisoning can cause similar symptoms to autism, the two were thought to be related. In 1999, the U.S. Public Health Service and the AAP requested that vaccine manufacturers solve this problem by reducing or eliminating thimerosal from their vaccines.
Further studies, including one published in The New England Journal of Medicine in 2004 and another published in Pediatrics in 2010, have shown no link between thimerosal and autism. They found that babies who were exposed - both in the womb and from birth to 20 months - to high levels of thimerosal had the same likelihood to develop autistic tendencies as those who were not exposed to thimerosal at all.
So are vaccines linked to autism? Some researchers continue to search for a causative connection between the two, but current research does not support this link.
This post is part of the series: Autism Research for Parents
Are you interested in the dynamics of how autism works? This series contains several articles that discuss what researchers have discovered or theorized about autism, especially those issues relevant to parents and caregivers.