Scientific Method / Science & Exploration

Court sides with science, says no vaccine-autism link

The special court overseeing the US National Vaccine Injury Compensation …

Yesterday, the United State's Vaccine Court Omnibus Autism Proceeding delivered its ruling to three families who claimed that vaccines were the cause of their children's autism. The courts ruled that "the evidence does not support the general proposition that thimerosal-containing vaccines can damage infants' immune systems," thereby ending the case the parents brought before the special court.

The ruling came down not from a single jurist on the bench, but a panel of three "special masters" who were appointed to determine if Michelle Cedillo, Colten Snyder, and William Yates Hazlehurst's autism was caused by either the measles-mumps-rubella (MMR) vaccine or the vaccine preservative, thiomersal. These three families were test cases who represented more than 5,000 families that have brought cases before the special court. Each is seeking compensation under the National Vaccine Injury Compensation Program, a no-fault program funded by a $0.75 per dose tax that is used to pay for injuries resulting from vaccinations.

The concept that the MMR vaccine can cause autism was first proposed by Andrew Wakefield, a British surgeon, and his theory was subsequently picked up by the British media and hyped across the world, causing parents to question whether or not it is in their children's best interest to get vaccinated. Even though numerous subsequent scientific studies were unable to replicate the original results, the hysteria surrounding autism and vaccines remains—to the extent that herd immunity is dropping to dangerously low levels in some areas. Today's ruling put the largest US vaccine court squarely on the side of good science.

Start of a scare

The entire MMR-autism scare started in 1998 when Wakefield and eleven coauthors published a paper in the medical journal The Lancet claiming that they found measles virus RNA in the bowel tissue of children with autism spectrum disorders (ASD).

While this was a shocking result, further scientific studies could not find any evidence that linked MMR to either gastrointestinal disturbances or ASD. In the intervening years, as the scientific evidence against this concept mounted, it was discovered that Wakefield was taking money from lawyers seeking to sue vaccine manufacturers on behalf of autistic children years before he began his research. The Lancet retracted the paper and 10 of 11 of the co-authors petitioned to have their names taken off the study. And it was revealed earlier this week that Wakefield fudged the data. Even in the face of this, people still clung to the fact that MMR vaccine had the potential to cause ASD, along with a host of other possibilities.


One reason that people latch onto this idea is because of the
temporal proximity of children getting vaccinated and being diagnosed
with ASD; both occur around the age of 18 months. In the UK,
immunization rates fell by over 10 percent after the scare, and in 2007 the country saw
its first measles death in over 14 years. With pundits
and celebrities pushing their cause of attempting to link autism and MMR,
there is still a great deal of uncertainty in the public's mind.

Hopefully the nail in the MMR-ASD coffin has been hammered home in the past six months. Last September, a group of researchers tried a new tactic; they sought to reproduce Wakefield's exact study using much newer and more sensitive techniques. They found absolutely no data to support the idea that measles viruses from the vaccine could be found in bowel tissue or potentially lead to an ASD diagnosis.

Then, just last week, the results of an investigation were published in the Sunday Times and showed that not only was Wakefield's study flawed, but he faked and fudged data that went into the final report.

Maybe preservatives?

With the MMR-ASD link thoroughly debunked, at least from a journalistic and scientific point of view, one other bogeyman remained a possibility: the presence of mercury in vaccines. In order to keep vaccine doses sterile and free of harmful invaders—bacteria and fungi—thiomersal (also known as "thimerosal in the US") was added as a vaccine preservative in the late 1920s.

While thiomersal is a compound that contains mercury, and it is known that certain forms of mercury are harmful, there has been no scientific study to date to show that thiomersal in vaccines is harmful or leads to autism.


While thiomersal contains mercury, it is not (apparently) harmful as a chemical compound. Thiomersal is known to degrade into ethyl mercury, which is not known to be toxic to humans as it is not readily adsorbed and is efficiently excreted.

Much of the worry surrounding this topic comes from people trying to link ethyl mercury to methyl mercury, a similar compound, but one with a vastly different pharmacokinetic pathway. Methyl mercury is known to be acutely toxic due to its ability to bind to proteins and traverse the blood brain barrier leading to poisoning.

In order to alleviate fears over mercury in vaccines, the US government and many EU governments removed thiomersal from most vaccine supplies by the late 1990s and early 2000s (2001 in the US). Despite this, autism rates have continued to rise across the US. The cause for this is still under dispute; whether there is some other trigger or simply a broadened diagnostic criteria for what qualifies as ASD is hotly debated. A recent study, however, found that broadened criteria alone could not explain the ever-increasing number of diagnoses.

While the court's ruling today should come as no surprise to anyone who has followed the science behind this entire ordeal, it will hopefully reassure parents who may have been worried about vaccinating their children. Writing in the opinion for the court, Special Master George Hastings roundly criticizes the doctors who are pushing the vaccine-autism link. "Unfortunately, the Cedillos have been misled by physicians who are guilty, in my view, of gross medical misjudgment," he wrote. "I further conclude that while Michelle Cedillo has tragically suffered from autism and other severe conditions, the petitioners have also failed to demonstrate that her vaccinations played any role at all in causing those problems."

The American Medical Association released the following statement in response to today's ruling: "We need ongoing research into the causes of autism, but cannot let unfounded myths keep us from giving our children the proven protection they need against infectious diseases."

Various autism awareness groups, while not in complete agreement with the ruling, do agree that further research is needed into the underlying causes of autism and ways to help individuals and families live with it.

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