July 9, 2004

Does mercury in vaccines cause autism in children? A definitive answer has so far proven elusive. No one can say with certainty that thimerosal, the vaccine preservative made with 49.6% mercury, helped fuel the explosion in cases of autism, attention deficit disorder, speech delay and other disorders over the past decade. But no one can say for certain that it did not.

On May 18, 2004, the respected Institute of Medicine issued a much heralded report stating that the bulk of evidence “favors rejection of a causal relationship” between thimerosal and autism.[i] The independent panel, commissioned by the government to investigate alleged links between vaccines and autism, delivered a harsh blow to advocates of the thimerosal-autism hypothesis. But despite its authoritative certainty, the report failed to close the books on this simmering medical controversy. Indeed, recently published animal and test tube studies provide compelling biological evidence of harm (though certainly not proof) from thimerosal containing vaccines.

Exactly five years ago, the federal government disclosed that most American children were being exposed to levels of mercury in vaccines above federal safety limits. Since then, officials moved to phase out mercury from childhood vaccines, and to determine if thimerosal exposure in infants could cause autism and other neurological developmental disorders. To date, neither goal has been fully attained.

Thimerosal has been removed from most routine vaccinations given to American children. But it is still found in the majority of flu shots, which the US government now recommends for pregnant women and children between 6 and 23 months of age.[ii] In 2004, the Centers for Disease Control and Prevention declined to state a preference for mercury-free flu shots in infants.[iii] Mercury is also found in tetanus, diphtheria-tetanus, pertusis and meningitis vaccines, which are sometimes, though not routinely given to children. It is also still used in many over-the-counter products, including nasal sprays, ear and eye drops, anabolic steroids, and even a hemorrhoid treatment.[iv]

Meanwhile, the CDC has been unable to definitively prove or disprove the theory that thimerosal causes autism, ADD, speech delays or other disorders. Several studies funded or conducted by the agency have been published in the past year, all of them suggesting that there is no connection between the preservative and the disorder. The CDC insists that it looked into the matter thoroughly and found “no evidence of harm” from thimerosal in vaccines.

But “no evidence of harm” is not the same as proof of safety. No evidence of harm is not a definitive answer; and this is a story that cries out for answers.

Why would a trusted health agency allow a known neurotoxin to be injected into the bloodstream of small babies --  in amounts that exceed federal safety exposure levels for adults by up to 50 times per shot? It’s a disturbing question, and there are no satisfying answers.

But a small group of parents, aided by a handful of scientists, physicians, politicians and legal activists, spent the past five years searching for answers. Despite heavy resistance from the powerful public health lobby, the parents never abandoned their ambition to prove that mercury in vaccines is what pushed their children, most of them boys, into a hellish, lost world of autism.

            Of course, there are two sides to every good story, and this one is no exception. For every shred of evidence the parents and other researchers have unearthed linking thimerosal to autism, public health authorities have produced forceful data to the contrary.

The parents and their allies accuse public health officials and the pharmaceutical industry of negligence and incompetence, at best, and malfeasance and collusion at worst. 

On the other hand, the mercury-autism proponents have been greeted with contempt and counterattack by many in the American health establishment, which understandably has an interest in proving the unpleasant theory wrong.

Each side accuses the other of being irrational, overzealous, blind to evidence they find inconvenient, and subject to professional, financial or emotional conflicts of interest that cloud their judgment. In some ways, both sides are right.

            Some children with autism were never exposed to thimerosal, and the vast majority of people who received mercury in vaccines show no evidence of harm whatsoever. But if thimerosal is not responsible for the apparent autism epidemic in the United States, then it is incumbent upon public health officials to mount a full-scale quest to identify the actual cause. At the very least, the thimerosal debate has compelled the scientific community, however reluctantly, to consider an environmental component to the disorder, rather than looking for a purely genetic explanation. Autism, by most accounts, is epidemic. And there is no such thing as a genetic epidemic

Something in our modern world is apparently pushing a certain number of susceptible kids over the neurological limit and into a befuddling life of autism and other brain disorders. Several potential culprits beside thimerosal have been mentioned, though there is no hard evidence to link any of them to autism. Possible environmental “triggers” include: mercury in fish, pesticides, PCB’s, flame retardants, jet fuel, live viruses in vaccines or some as-yet unidentified virus, and even rampant cell phone use. It is plausible that any combination of the above, with or without thimerosal exposure added into the mix, might cause harm to some fetuses and infant children.

But so far, only thimerosal exposure has been studied to any significant degree in children (with the exception of the measles-mumps-rubella vaccine, or MMR). This book looks at evidence presented on both sides of the thimerosal controversy, but told from the parents’ admittedly subjective point of view. Perhaps this story will be told one day from the opposing view, from the doctors, bureaucrats and drug company reps who claim nothing more than the laudable desire to save kids from the ravages of childhood disease.

But many of the public health officials who discount the thimerosal theory were unwilling (or prohibited by superiors) to speak on the record for this book. Readers are invited to reach their own conclusions on the evidence.

Did the injection of organic mercury directly into the developing systems of small children cause irreparable harm? It’s a plausible proposition, and a hugely important question. If the answer is affirmative, someone will have to pay to pick up the pieces.

Why did the CDC and the Food and Drug Administration allow mercury exposures from childhood vaccines to more than double between 1988 and 1992, without bothering to calculate cumulative totals and their potential risks?

Why, for that matter, was there a corresponding spike in reported cases of autism spectrum disorders? Why did autism grow from a relatively rare incidence of 1 in every 5,000 births in the 1980s, to 1-in-500 in the late 1990s. Why did it continue to increase to 1-in-250 in 2000, and then 1-in-166 today?[v] Why are rates of ADD, ADHD, speech delay and other childhood disorders also rising, and why does one in every six American children have a developmental disorder or behavioral problem?[vi] And why does autism affect boys at a 4-to-1 ratio over girls?[vii]

Autism traditionally has been a disease of industrialized nations, at least until recent years. But not all Western countries have autism epidemics. Autism spectrum disorder in the United States, with 60 per 10,000 (1-in-166) kids now affected, is much more prevalent than it is in northern European countries such as Denmark, which removed thimerosal from vaccines in 1992 and now reports just 7.7 per 10,000 children (or 1-in-1,300). The UK, meanwhile, which just announced that it will remove mercury from vaccines in September, 2004, reports exactly the same prevalence of ASD – 1 in 166 children -- as the United States.[viii]

This is not an anti vaccine book. Childhood immunization was perhaps one of the greatest public health achievements of the 20th Century, and vaccines will continue to play a crucial role in our lives as we enter an uncertain age of emerging diseases and potential bioterrorism.

Some parents, fearing harmful effects, have been tempted not to vaccinate their children. Most people would agree that this is foolhardy and dangerous. Few of us are old enough to remember the great epidemics of influenza, pertussis, smallpox, polio, diphtheria and measles that once swept entire populations - until the advent of vaccines reduced those maladies to abstract, unthreatening concepts, at least in America. These diseases, all of them preventable, can kill children. When vaccination rates fall, disease rates rise.

Nor should this book be regarded as politically partisan in nature. Though some people in the book do launch harsh criticisms against the Bush Administration and Republican leaders in the Senate, two leading protagonists – from these parents’ point of view – are among the most conservative members of Congress. Moreover, much of the story here took place under the Administration of President Bill Clinton.

            Parental fear of vaccines has threatened the viability of the US National Immunization Program. But if scientists prove that mercury in vaccines was at least partly to blame for much of the autism epidemic -- and that the culprit has been largely (or one day entirely) removed -- then confidence in childhood immunization should return to comfortable levels.

But most health officials insist that mercury in vaccines is harmless, even as warnings go off about the toxic effects on infants and fetuses from mercury in fish.

This mixed message is doing nothing to bolster faith in the immunization program.

Many vaccines come in multi-dose vials, which cannot be sold without a preservative, such as thimerosal. Because of its mercury content, thimerosal prevents bacterial and fungal contamination in vials that undergo repeated puncturing of the seal by needles. Thimerosal is not required for single-dose vials, nor is it found in live vaccine preparations, including MMR, which contains live organisms.

Thimerosal was marketed for vaccines the 1930s and remained the preservative of choice in the US throughout the 20th century. Mercury-free solutions were developed, but never widely used. The reason is thought to be economic.

Developing alternative preservatives, and having them tested and approved by the FDA is a costly proposition. Switching to single dose vials, another alternative, is viable. But it is also expensive and more cumbersome for transportation and storage. Finally, thimerosal is often used in vaccine manufacturing itself, to preserve sterility in the lab. Since it was already in vaccines, it didn’t make much sense to seek out an alternative. And at any rate, the FDA and CDC never said that thimerosal might be hazardous.

Curiously, the first case of autism was not recorded until the early 1940’s, a few years after thimerosal was introduced in vaccines. It was described by psychiatrists Leo Kanner and Hans Asperger, who independently coined the terms 'autism' and 'autistic' respectively. The term comes from the Greek word for self, autos.

In the late 1940's, Austrian-born psychologist Bruno Bettelheim proposed that autistic children came from aloof mothering; they were byproducts of women who could not or would not provide the warmth and emotional support needed for the normal development of a child. He labeled these women “refrigerator mothers,” a term that stuck until the 1960s.

In 1964, Bernard Rimland, a psychologist and father of an autistic son, wrote a groundbreaking book called Infantile Autism: The Syndrome and Its Implications for a Neural Theory of Behavior. The book is widely credited with debunking the refrigerator mother theory, which today seems both laughable and insulting to many parents. The book helped convince the psychiatric community that autism was not an emotional problem at all, but rather a biological one.

In the 1980s, suspicions began to surface among some parents of autistic children that vaccines were somehow involved in the disorder. In 1985, Barbara Loe Fisher, co-founder of the National Vaccine Information Center, co-authored a book (with H. L. Coulter) called A Shot in the Dark. In the course of her research she found many children who developed autism after a reaction to the diphtheria-pertussis-tetanus (DTP) shot. 

            Vaccines continued to remain on autism’s radar screen, and were raised to new notoriety when a young English doctor named Andrew Wakefield said that the measles-mumps-rubella (MMR) live-virus vaccine (which does not contain thimerosal) might be contributing to regressive autism in children.

Then in July, 1999, came the US government announcement about mercury levels in childhood vaccines.

Now the stakes could not be higher. Perhaps billions of dollars in litigation is pending against drug companies involved in vaccine production. The deep pocketed pharmaceutical industry has extended its financial largesse to politicians and scientists around the country, in open pursuit of indemnity against lawsuits and, some charge, in a darker effort to suppress evidence of thimerosal’s toxicity.

Meanwhile, the reputation of American public health is on the line.

            The jury is still out on thimerosal, but deliberations are well under way. One side will emerge vindicated, and the other will earn eternal scorn in the medical history books.

In November, 2003, the father of an autistic boy in North Carolina, an anti-thimerosal activist and a believer, approached a well-known pediatrician after the doctor had delivered a lecture on the safety of vaccines in general, and thimerosal in particular. 

“You know something doctor?” the father said. “If it turns out that you are right, then I will personally come down to your office and apologize to you with every fiber of my being.”

“But if it turns out that you are wrong,” he added, “then you are going to hell.”



[i] Immunization Safety Review: Vaccines and Autism (2004), Executive Summary, Institute of Medicine, Committee on Immunization Safety, National Academies Press.

[ii] “Prevention and Control of Influenza: Recommendations of the Advisory Committee on Immunization Practices,” Morbidity and Mortality Weekly Report, Centers for Disease Control and Prevention, May 28, 2004.

[iii] Ibid.

[iv] “Mercury in Drug and Biologic Products,” U.S. Food and Drug Administration, Center for Evaluation and Research (CBER), August 5, 2003; updated March 30, 2004.

[v] Sources for 1 in 5000 figure: Only two autism prevalence studies were conducted in the US in the 1980’s: one showed a rate of 1 case per 10,000 children, and the other showed a rate of 3.3 per 10,000, (or 1 in 3,030). This typically has been averaged out to 2 per 10,000, (or 1 in 5000). Source for 1 in 500 figure: Marie Bristol, et al, “State of the Science in Autism: Report to the National Institutes of Health,” Journal of Autism and Developmental Disorders, 1996, Vol. 26, No. 2, pp. 121-157. Source for 1 in 250: In 2002, the CDC conducted a prevalence study in Brick Township, NJ, showing a rate of 4 per 10,000 (or 1 in 250), CDC, National Vaccine Program Office, Vaccine Fact Sheet on Autism. Source for 1 in 166 figure: “Autism A.L.A.R.M." – U.S. Department of Health and Human Services, CDC, The Medical Home Initiatives and First Signs.

6 “Autism A.L.A.R.M." – U.S. Department of Health and Human Services, CDC, The Medical Home Initiatives and First Signs.

[vii] C. Gillberg C, M. Coleman “The Biology of the Autistic Syndromes - 2nd Edition, Mac Keith Press, 1992, Page 90. (SEE: Bernard et al, 2000).

[viii] Denmark source: “A Population-Based Study of Measles, Mumps, and Rubella Vaccinations and Autism,” Madsen, et al, The New England Journal of Medicine, Vol. 347, No. 9 - November 7, 2002, pp. 1481. UK source: “MRC Review of Autism Research – Epidemiology and Causes,” Medical Research Council, UK, December, 2001.

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