Monday, October 26, 2009

Bad Science: Vaccines and Autism

The town of Protection lies just before the Red Hills of Southwest Kansas, an area of rugged scarlet gypsum crags that looks as if it came straight from the Acme-painted landscape of a Road Runner cartoon. It’s a small town of about 500 people, and with apologies to John Mellencamp it’s like most small towns in rural America…one bank, two restaurants, a tribute gallery to the local boy made good (in this case Stan Herd, the crop artist…stop laughing and check out; a town that’s aging, hurting, patiently awaiting it’s long-known fate. Nobody knows how the town got it’s name. One version says it was the result of a joke, when cowboys faked an Indian raid to frighten the settlers and the townspeople collected under a bluff for protection. There’s another story, and a better one, too:

"About a year later a post office was started on the Kiowa and called Protection. Among the prominent members of the old Protection Town Company were E. P. Hickok, W. P. Gibson, J. W. Johnson and one or two others, all republicans, good and true. When it came to selecting a name for the new post office, there was some difference of opinion, and it was finally agreed to leave the naming to the postmaster general, who was a republican also. In the political platforms of those days there was much said in regard to "protection," as compared with "free trade," when speaking of the development of American industries and the employment of labor, and it was but the natural thing for the postmaster general to think of the word "Protection" for the new post office on the Kiowa in Comanche-co., Kansas. That, as I understand it, was how the city of Protection got its name." -- Hiram O. Holderby, The Western Star, April 8, 1921.

Even then, Kansans were nothing if not conservative.

The town of Protection is important because its name led the National Polio Foundation to make it the first community in the United States to have everyone under 50 years of age immunized against polio. Today, we can’t conceive of what threat polio was to children, especially during the summer. My father recalls times when no one was allowed to use public swimming pools or engage in other summer fun because of the spectre of polio. And while many of us have seen pictures of Franklin Roosevelt (probably the world’s most famous victim…and conqueror…of polio), the only way today to get a sense of what polio was like is to lay for a time in an old iron lung and imagine that you may, or may not, be able to leave it. Now imagine yourself, or your son or daughter, lying there as an uncomprehending four-year old. The advent of the Salk injectable polio vaccine, and the Sabin oral vaccine that followed, resorted the joy of childhood for millions in this nation and around the world.

Immunizations are one of the true success stories of public health. Most authorities would rank vaccination and the provision of clean drinking water as the top two achievements in health over the last century, besting antibiotics, hospital care, or surgery. (A health wonk like me would want to point out that, according to the CDC, fully 25 of the 30 additional years of life expectancy over the last 125 years have come from the world of public health, and not from the health care system.) Vaccines work so well that when there is an even a small outbreak of measles or mumps, it becomes newsworthy. Vaccination is proof that science works. So it’s disturbing to see that bad science is being used to link vaccines…and specifically a preservative contained within vaccines called thimerosal… with neurodevelopmental disorders such as autism. It’s especially worrisome when aggressive vaccination is one of the key tools we have to prevent the further spread of pandemic H1N1 “swine flu.”

The concern over mercury compounds such as thimerosal is linked to the idea that the presence of these chemicals in vaccine products can retard neurologic development, and more specifically results in autistic disorders (clinicians refer to autism not as a specific condition, but as a term applying to range of problems known as “autistic spectrum disorders,” or ASD). It is true that there is a correlation between total body exposure to mercury and impaired neurologic development. As a result, in 2001 the Institute of Medicine (IOM) recommended that thimerosal be removed from all vaccines administered to infants, children, or pregnant women in the U.S.

On the surface, that single recommendation would suggest the case is closed. There’s a link, the Institute of Medicine said to remove the thimerosal, and why would they do that if it wasn’t the cause of autism and other developmental delays?

The spinmeisters keep trying to tell us the world works in sound bites, but most of us know better than that. Sound bites represent a fraction of the larger discourse, just as exposure to mercury in one venue does not reflect the total exposure to this element. A careful reading of the IOM report shows that the recommendation was a precautionary step to limit the cumulative exposure infants might have to ethyl mercury. The concern of the IOM was not based on the dose within the vaccine, but on the cumulative dose of mercury received from environmental exposures, such as eating fish laced with industrial mercury wastes and mercury leeching into the fetus from dental amalgams. This hypothesis is supported by studies that document a lack of link between thimerosal in vaccines and the development of neurologic disorders, but suggest that cumulative environmental mercury exposure raises the risk. The IOM felt that the mercury in vaccines was a controllable exposure, whereas that in the environment at large was not. Therefore, as non-mercury alternatives could be identified, they should be used. Their recommendation was seen as a step towards mitigating a larger problem, and certainly not as a “cause-and-effect” solution unto itself.

Nonetheless, there continues to be a belief that any mercury in a vaccine is necessarily the cause of neurologic abnormalities, especially when used in combination with the MMR (measles, mumps, and rubella) vaccine. Knowing that measles virus can cause encephalitis in severe cases of clinical illness, the theory contends that measles virus is absorbed into the body through the vaccine and that the thimerosol in the vaccine product both alters the appropriate immune response and poses a direct toxic effect, resulting in an inflammation of cerebral tissues resulting in autism. Much of this belief comes from the work of Dr. Andrew Wakefield, a British doctor who led the initial works claiming a link between autism and the MMR (measles, mumps, and rubella) vaccine. While the studies were ripe with flaws, press coverage insured that the effects of his work on vaccine uptake in the United Kingdom were immediate and significant. A Canadian source notes that, “At one point MMR vaccination rates sunk to 75 per cent in Britain, well below the 95 per cent authorities say is needed to keep these diseases from circulating. While the rate has since climbed to about 85 per cent, Britain continues to suffer outbreaks of these three diseases and to seed the diseases abroad (, July 16, 2007).” We’ve seen similar things happen in the United States as a result of unthinking publicity. For example, Kansas saw that in the summer of 1999, there was a dramatic drop in the number of Kansas newborns receiving immunization against Hepatitis B after a recommendation to suspend vaccination with this agent due to thimerosal content in the vaccine. A thimerosal-free product was released four moths later, but even now we still have yet to see a return of vaccination rates to 1999 levels.

(Interestingly, the Wakefield saga continues to this day. In 2004, ten of his collaborators retracted the work, and it was later revealed that Wakefield was doing research for pay on behalf of parents who were seeking legal damages from vaccine companies. He had also taken out a patent for a new form of the vaccine, providing possible incentive to bias his results. He is now facing revocation of his medical license from the British General Medical Council.)

The medical community, recognizing the value of vaccination, was quick to respond. A brief search through the National Library of Medicine collection revealed over 130 papers reviewing the links between thimerosal, vaccines, and neurologic development within the past decade, and both the United States Centers for Disease Control and the Institute of Medicine have reviewed the issue in depth.

The bottom line is that the studies have failed to establish a firm link between exposure to thimerosal in childhood vaccines and the development of neurologic disorders. One of the best works was performed in Denmark to review the incidence of autism in over 500,000 children before and after the advent of laws mandating that all vaccines be free of thimerosal. In that nation, the incidence of autism continued to rise despite the lack of thimerosal in the vaccinations (JAMA 2004; 291:180-1). On our side of the pond, the California Department of Public Health just this year published work which demonstrated identical results (Arch Gen Psych 2008; 65:19-24). Clearly, there is something that is behind the rise in these developmental disorders. It may be environmental, genetic, or (I suspect) related to both the appropriately increased awareness and diagnosis of the spectrum of ASD as well as the harmful societal urge to “medicalize” behavioral issues in order to divert accountability. But there certainly appears to be no cause-and-effect link between vaccine use and the development of autism.

As might be expected in this country, the vaccine-mercury-autism issue has a legal dimension as well. Over 5,000 families have filed adverse event claims with the National Vaccine Injury Compensation Program (NVICP), claiming a causal link between the MMR vaccine, thimerosal within the vaccine, and neurodevelopmental delay. Three test cases were selected for adjucation, and in all three cases claims for compensation based on an alleged thimerosol-autism link were denied early this year by Special Masters appointed by the United States Court of Federal Claims. (In all three cases, the denial was upheld on appeal.) The basis for these denials was well summarized as follows:

“After considering the record as a whole, I hold that petitioners have failed to establish by preponderant evidence that (the child’s) condition was caused or significantly aggravated by a vaccine or any component thereof. The evidence presented was both voluminous and extraordinarily complex. After careful consideration of all of the evidence, it was abundantly clear that petitioners’ theories of causation were speculative and unpersuasive. Respondent’s experts were far more qualified, better supported by the weight of scientific research and authority, and simply more persuasive on nearly every point in contention. (The) parents brought this action in good faith and upon a reasonable basis. However, they have failed to demonstrate vaccine causation of (the child’s) condition by a preponderance of the evidence.”

(United States Court of Federal Claims, Office of Special Masters, No. 01-162V, February 12, 2009)

All this being said, most of those involved in the debate still don’t recognize that since 1999, the only commonly used childhood vaccines containing thimerosal are the influenza vaccine (and specifically only the vaccine found in multi-dose vials) and the combination vaccine against both hepatitis A and B (there are thimerosal-free forms of vaccines against only hepatitis A or B, but none in combination). In many ways, the thimerosal question is one of the past and not of the present.

From a public policy standpoint, it’s not just the concern of bad laws being derived form bad science. Laws requiring all vaccines to be mercury-free may impact the ability of state and local governments to prepare for public health outbreaks such as the current spread of H1N1 influenza. While thimerosal-free influenza vaccine is available, in recent years only about 10%of the total supply is manufactured in that form. The most cost-effective and efficient way to immunize children against this virus is through the use of multi-dose vials that contain thimerosal. Children do die of influenza and its complications, and the limitations of these policies mean that children may be at risk of not being able to receive the vaccine they need.

Some proposals may truly enter the realm of “unintended consequences.” Several years ago, there was a bill proposed to eliminate the use of any drug product containing mercury in Kansas. This meant that adults, as well as children, may not be able to receive influenza vaccination from multi-dose vials. They may also not be able to receive travel vaccinations such as those against encephalitis. Snake and spider antivenins also contain mercury products as preservatives, as do many prescription and “over-the-counter” products for the eyes, ears, and nose. We’re fortunate that in Kansas, the legislature has not passed any such bills out of committee.

So if the science is bad and the thimerosal is gone, why are we having this dispute? In my view, this is one of those areas in public policy where personal passion meets the public stage. I’m very blessed to have a happy and healthy eleven-year-old boy. If my son had autism, I’d be doing exactly what the proponents of these laws are doing. I’d be looking for an answer, something that I could see as a cause for the condition, and I’d be doing what I could to prevent it from happening to others. Knowing that, hearing the heartbreak in these parent’s voices and seeing them struggle with their children, it’s hard to look at the issue objectively. I just wish I could agree.

No comments:

Post a Comment