Science Trumps Fear Over Autism

by Amy Spangler
February 05, 2010

Perhaps Andrew Wakefield, MD didn’t realize that his 1998 study erroneously linking vaccinations to autism would ignite a decade long controversy. But he should have. If not for the media frenzy fomented by high profile celebrities, the scientific method might have triumphed long ago. Journalists should know better. Yet given the scope of the damage, any claim of vindication would ring hollow. In the end, science prevailed, but at what cost?

After the United Kingdom General Medical Council (GMC) described the actions of Andrew Wakefield, MD, and two of his colleagues as dishonest and irresponsible, The Lancet, a respected medical journal, did something it has only done 10–15 times in its 186-year history, it fully retracted a study by Wakefield and colleagues from the published record.

In 1998, claiming to have found a possible link between autism and the measles-mumps-rubella (MMR) vaccine, Andrew Wakefield and 13 co-authors ignited a firestorm of controversy. Parents fearing that their children would become autistic, refused to have them vaccinated. Lawyers eager to place blame, filed class action lawsuits. Both sides launched personal attacks.

Five years later, 10 of the 13 co-authors disavowed the findings. Last year, the United States (US) vaccine court ruled against those claiming that there was a link between vaccines and autism. Countless research dollars have been spent on rigorous studies aimed at refuting Wakefield’s findings. Fears over a reemergence of diseases like polio and measles should children go unvaccinated are being realized. And most important, the rate of autism has continued to climb.

The California Department of Developmental Services analyzed data on childhood autism from 1995–2006. The rate of autism at age 3 for children born in 1993 was 0.3 per 1,000 births; among children born 10 years later the rate was 1.3 per 1,000 births; by 2006, 4.5 out of every 1,000 children born in 2000 were estimated to have autism.

Arthur Allen was one of the first to write about the thimerosal controversy in an August 2002 report published in New York Times Magazine. Allen’s report was followed in June 2005, by a series of articles by Robert Kennedy, Jr. in Rolling Stone and Salon.com, in which Kennedy accused government scientists and their academic colleagues of covering up indisputable evidence of a causal link between thimerosal and autism. That same year, Evidence of Harm: Mercury in Vaccines and the Autism Epidemic, A Medical Controversy by David Kirby was released. One critic described Kirby as “an author subtly influenced by the vaccine paranoia people” and cautioned readers to “beware of books like these because they lead with fear and not knowledge.”

Arthur Allen, in response to the Rolling Stone article by Kennedy stated, “Aside from a June 25 New York Times article that discussed the parallel realities of parents and scientists studying thimerosal, there has been little mainstream media response. Considering that about 9,000 lawsuits of claims have been filed against thimerosal and have the potential to wreck the pharmaceutical industry, the debate has high stakes.”

What is thimerosal?
Thimerosal is an organic compound that contains ethyl mercury. It has been used in vaccines since the 1930s to prevent bacterial and fungal contamination. Thimerosal extends the life of vaccines and allows them to be packaged in multi-dose vials.

Thimerosal contains mercury, a toxic metal. Mercury occurs naturally in the environment (air, soil, water). It has been found in fish (particularly long-lived fish such as sharks, tilefish, king mackerel, and swordfish) and in small amounts in animal tissues (humans). Dental fillings often contained Mercury, as did thermometers, and vaccines. If large amounts of mercury accumulate in the body over time, death can occur. The Environmental Protection Agency (EPA) has established tolerance levels for mercury based on studies of methyl mercury. The EPA tolerance level is 10 times less than the lowest level calculated to cause harm.

Mercury exists in several forms: metallic mercury, inorganic mercury, and organic mercury (methyl mercury, ethyl mercury, phenyl mercury). Thimerosal contains the organic mercury known as ethyl mercury. Nearly all of the research done on mercury toxicity has focused on the organic methyl mercury. Methyl mercury and ethyl mercury are closely related but they have important differences. Different forms of mercury have different health effects. Methyl mercury has a half-life of 50 days and accumulates in the body. Ethyl mercury has a half-life of 7–10 days and is less likely to accumulate in the body. Also, ethyl mercury is converted in the body into inorganic mercury and excreted in the stool.

In 1999, the U.S. Food and Drug Administration (FDA) determined that children receiving all of the routinely recommended childhood vaccines would potentially exceed the Environmental Protection Agency (EPA) tolerance levels for mercury (levels based on studies of methyl mercury). So in the interest of safety and out of concern that misinformation regarding thimerosal would lead to widespread refusal of vaccines, the FDA asked vaccine manufacturers to eliminate or reduce the mercury content of vaccines.

Since 2003, all routinely recommended childhood vaccines have been thimerosal-free. Only one childhood vaccine still contains trace amounts of thimerosal (influenza vaccine). Because thimerosal-containing vaccines produce levels of mercury in adults that are so low, experts do not recommend removal of thimerosal from vaccines intended for use in adults and adolescents.

Manufacturers now bottle vaccines in single-dose containers taking care to ensure that the vaccines are not contaminated in the manufacturing and bottling process. This has increased the cost of vaccines and led to vaccine shortages. However, despite these concerns, public health officials are committed to providing thimerosal-free vaccines.

What is autism?
Autism Spectrum Disorders are a group of developmental disabilities that are caused by an abnormality in the brain. According to the Centers for Disease Control and Prevention (CDC), 2/1000 to 6/1000 children have an Autism Spectrum Disorder (ASD). ASDs range from a severe form, autistic disorder (classic autism) to a mild form, Asperger syndrome. If a child has symptoms of either disorder but does not meet the specific criteria of either, he/she is diagnosed with pervasive developmental disorder not otherwise specified (PPD-NOS).

Classic autism affects verbal and nonverbal communication and social interaction. It is usually evident before age three, and can negatively affects educational performance. Characteristics of autism include irregularities and impairments in communication, engagement in repetitive activities and stereotyped movements, resistance to environmental change or change in daily routines, and unusual responses to sensory experiences.

Genetics is thought to play a key role in the development of autism. Using a broad definition of autism, when one twin has autism, approximately 92 percent of identical and 10 percent of fraternal twins have autism, suggesting that autism has a genetic component.

Home movie studies provide some of the best data on when symptoms of autism first appear. In one particular study, home movies were taken of children who eventually were diagnosed with autism and children who were not diagnosed with autism. The movies were made before the children received the MMR vaccine. Neurodevelopment specialists viewed the movies and were consistently able to separate autistic from non-autistic children at one year of age. Using sophisticated movement analysis, movies of children eventually diagnosed with autism and children not diagnosed with autism were coded and evaluated for their capacity to predict autism. Children who were eventually diagnosed with autism were predicted from movies taken at 2–3 months of age. These data clearly show that subtle symptoms of autism are present in early infancy and argue against vaccines as a cause of autism.

Some evidence suggests that autism occurs as a result of in utero events such as viral infection. Children exposed to thalidomide during the first or early second trimester were found to have an increased incidence of autism. Autism has been observed in children with ear, but not arm or leg abnormalities. Because arms and legs develop after 24 days’ gestation, it was concluded that the risk period for autism following receipt of thalidomide must be before 24 days’ gestation.

Researchers have also reported an increased risk for autism in children with congenital rubella syndrome and tuberous sclerosis, suggesting that autism involves abnormalities of the central nervous system that occur in utero.

Scientists at the University of California Davis’ M.I.N.D. Institute are investigating whether environmental exposure to chemicals, pesticides, and metals during pregnancy can lead to autism.