Pediatric Vaccines and Autism

Autism is a complex developmental disorder that generally appears in the first three years of life and is estimated to occur in 2/1,000 children. It is broadly characterized by impaired communication skills and social interactions, inappropriate attachments to objects or routines, repetitive actions, and inappropriate or aberrant responses to verbal cues, pain, danger, and change.(5,6) The condition is poorly understood and its causes largely unknown, though some suspect genetic components and obstetric complications.(7)

In the last decade, suspicion arose about a link between pediatric vaccines and autism. More specifically, many individuals have attempted to prove causal links between the measles, mumps, and rubella vaccine (MMR) and autism or, most frequently, between the vaccine preservative thimerosal and autism. This suspicion was prompted by clinical observations that the onset of autistic symptoms correlates temporally with the period during which children receive many vaccines, and was fueled by studies indicating that the rate of autism has increased significantly since the 1980s, a period over which the percentage of children receiving vaccines has also risen.(8,9) It is important to note that MMR vaccines do not now, nor did they ever, contain thimerosal. Thus, there are two separate issues to be addressed.

Where Did the Scare Come From?
Public awareness of the potential link between MMR vaccines and autism began with the 1998 publication in the medical journal Lancet of a study by A.J. Wakefield et al.(10) This study involved a case series of twelve patients at a referral clinic in England, all of whom had inflammatory bowel disease and autism. Dr. Wakefield’s hypothesis was that in some children the MMR vaccine provokes inflammation of the intestines, which then causes toxins to leak into the blood stream. These toxins presumably enter the brain, where they cause the damage that manifests as the clinical symptoms of autism.

Thimerosal, an ethyl-mercury salt, is a vaccine preservative that has been used since the 1930s to prevent bacterial contamination in multidose vaccine vials. Because mercury is a known neurotoxin, concerns about cumulative mercury exposure in children resulted in the 1999 decision to significantly reduce or eliminate thimerosal from pediatric vaccines manufactured for the U.S. market.(11) It is, however, still found in trace amounts in some pediatric influenza vaccines.(12) In addition to the temporal correlation described above, the concern over vaccines and autism was brought to the fore as the result of a 2000 study designed to test the hypothesis that autism is a unique form of mercury poisoning. This hypothesis, put forth by the executive director of Safe Minds, an anti-thimerosal autism awareness group, was based on observations that some of the clinical signs of mercury toxicity look similar to particular manifestations of autism.(13)

Despite the consensus of the overwhelming majority of scientists to the contrary, public concern persists that vaccines may be causally linked to autism, a situation worsened by the popular press’s failure to let sleeping dogs lie.

The Media Coverage:
Although the possibility of a vaccine/autism link has been soundly and repeatedly debunked by professional analyses of numerous studies, the press continues to capitalize on parents’ fears about the link by ignoring the science, and by presenting mixed messages. Virtually all media outlets continue to run stories about the alleged link, including ABC, CBS, NBC, MSNBC, the Associated Press, Reuters, PR Web, U.S. News and World Report, Newsday, the New York Times, Wall Street Journal, L.A. Times, Washington Times, San Francisco Chronicle, Chicago-Sun Times, People, and countless others. And that does not include the vast sea of websites posting articles on the topic.

Coverage has ranged from blatant scaremongering and dismissal of scientific evidence, to fairly unbiased assessments of the data.(14,15) One of the top offenders was CBS, which based one of its anxiety-provoking interpretations on a single study in which mice injected with thimerosal “developed profound problems” and “withdrew from their surroundings like autistic children.”(16,17) Other examples of unjustified alarmism in the media include statements found on PR Web, such as “Thousands of children are now mentally handicapped from their vaccines that contained thimerosal.”(18) Some outlets that correctly reported study findings seemed unwilling to accept them. For example, NBC ran a piece titled “No Link Between Childhood Vaccines and Autism,” yet after reporting the study findings went on to imply, via dramatic imagery of vaccine vials, dripping syringes, and a woman with her autistic son, that the jury is still out.

Nearly all medical professionals will tell you, however, that the verdict is in: thimerosal is “not guilty.” Nor is the MMR vaccine, which has been given comparatively more slack in 2004 than thimerosal on the autism issue, perhaps because the study that prompted the MMR scare was retracted and discredited by the journal in which it was published.

The Bottom Line:
While reporters are correct to present both sides of a debate, the problem has been one of emphasis. The overwhelming majority of scientists have declared the vaccine/autism link non-existent. But this is not the impression one would gather from the daily papers or nightly news. Not only are media outlets flawed in their repetition of the autism fears, they also frequently fail to report that a child’s risk of contracting a potentially deadly vaccine-preventable disease far outweighs the risk of he or she becoming autistic.

To date, all of the evidence supports the hypothesis that there is no link between MMR or thimerosal-containing vaccines and autism. This is the conclusion supported by the body of published peer-reviewed scientific literature, and the fact that the majority of reports linking these vaccines to autism do not meet the scientific criteria established to attribute causality.

In May 2004, after careful review and evaluation of the numerous studies regarding vaccines and autism, the Institute of Medicine (IOM)—a private, nonprofit organization that provides scientific advice to the government—issued a report in which a thirteen-member committee unanimously concluded that “the evidence favors a rejection of a causal relationship of thimerosal-containing vaccines and autism.” This expert panel came to the same conclusion regarding MMR vaccines and autism.(19)

The autism “epidemic,” as alarmists like to call it, has never been proven to exist. The increased rate of reported autism cases in the last fifteen years might simply be a result of higher recognition due to better diagnostic skills, broader diagnostic criteria, increased public and media awareness, and the inclusion of autism on the list of disorders meriting special education by the United States Department of Education.(20)

While it is justifiable and appropriate to search for an answer to the increased incidence of autism, it is unjustifiable and inappropriate, despite good intent, to unnecessarily alarm parents. This is especially true when their fear could actually compromise their children’s health. Alarmist media reports about the hypothetical risks from vaccination have prompted some parents to refuse immunization for their children, putting them at the very real risk of contracting vaccine-preventable diseases.

In all risk analyses, benefits must be weighed against risks. As Doctor David R. Smith, a board-certified pediatrician and former president of the Texas Tech University Health Sciences Center, aptly states, “Vaccines are the pinnacle of preventative health care.” They are one of the most successful public health measures in human history. Without a doubt, when it comes to vaccines, the real benefits outweigh the hypothetical risks.

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