Mercurial Vaccine Beliefs

A few weeks ago, I had a large debate with a fellow classmate about vaccines vis-a-vis their dangerous properties or lack thereof. He posited that the current vaccine scheduling in general, and the Measles-Mumps-Rubella (MMR) vaccine in specific, are plausible causes of the increasing rate of Autism
Spectrum Disorders (ASD) in the US and Western world. I realized, through speaking with him, that I really didn't know that much about vaccines, so researched it, and punked his bitch-ass like no ones business. So here is my sililoquey on vaccinations.

Many concerns have been raised over the past 10 years or so, the most vocal being those voiced by celebrity Jenny McCarthy and the MMR combined vaccination through her GenerationRescue organization. Her main points, to my understanding, have somewhat morphed as a body of evidence has mounted, but the gist is that thiomersal, --a mercury-containing compound once used as a preservative in some vaccines-- administration to young children is a causative agent of autism, and is responsible in large part for the increases in ASD in the US.
Vaccines are arguably one of the greatest successes of modern medicine. The eradication of small pox, polio (from the US), and even more recently, the decline of type B H. Influenzae from a common pediatric infection to <1% of it's 1997 incidence, attests to these successes. C. tetani, the bacteria that causes tetanus, exists nearly ubiquitously in the environment, and one can most certainly get tetanus without prophylaxis. Rotavirus is one of the leading viral causes of death in developing countries. So vaccinations are important to not only maintain prophylaxis socially, but to prevent individual contamination.

Now, thiomersal. This preservative has not been present in the MMR vaccine since 2000. It is absent from nearly all vaccines, and there are non-thiomersal containing vaccine alternatives available for every vaccine. Additionally, there is a mounting body of evidence contrary to Jenny McCarthy's hypothesis.



To make any sort of causative claim, a hypothesis, one must not only propose a link, but must also have a plausible underlying biological mechanism that would support their hypothesis, were it verified. McCarthy, et al., do not have a feasible mechanism for how thiomersal is causing autism. In fact, science knows very little about the pathophysiology of ASD, but we know a great deal more about the mercury toxicology, and thus far the ASD-Mercury mechanisms have been very flaky.

The most staggering refutation of the MMR-ASD link, however, comes from the research itself.

• The incidence of autism among vaccinated and unvaccinated children was comparted in a restrospective cohort study of all children born in Denmark between January 1991 and December 1998: 537,303 children. Among them, 838 (<1%) developed ASD, and 82 percent had received the MMR vaccine. After adjustment for potential confounders, the relative risk of ASD among unvaccinated children was 0.92 (95% CI, 0.68-1.24). The relative risk among the vaccinated children was 0.83 (95% CI). In addition to the lack of association between the MMR and ASD, no association was found between the age at the time of vaccination, the time since vaccination, or the date of vaccination and the development of ASD.(Thimerosal and the occurence of autism: negative ecological evidence from Danish population-based data. Pediatrics 2003 Sep;112(3 Pt 1):604-6)
• A population based study form the UK investigated the incidence of autism before and after the introduction of the MMR vaccine in 1988. Although there was a steady increase in the number of cases of autism by year of birth, there was no sudden change in the trend after the introduction of the MMR vaccine. Morover, there was no difference in the age of diagnosis of autism between the cases vaccinated before or after 18 months of age and those never vaccinated. The analysis failed to support a causal relationship between receipt of the MMR vaccine and subsequent development of Autism. A similar retrospective study in the US came to the same conclusions. (Time Trends in autism and in MMR immunization coverage in California. JAMA 2001 Mar 7;285(9):1182-5)
• In a population-based study from Montreal, rates of ASD increased as MMR vaccination coverage decreased. 
• In a total population study in Yokohama, Japan, the incidence of ASD among 31,426 children born between 1988 and 1996 increased from 48 to 117 cases per 10,000 children, despite the decline in MMR vaccination rate from 70% to 0% in 1993. 
• Other Sources: 
• A population based study of measles, mumps, and rubella vaccination and autism. N Engl J Med 2002 Nov 7; 347 (19):1477-82; 
• MMR vaccine and the incidence of autism recorded by general practitioners:a time trend analysis. BMJ 2001 Feb 24;322(7284):460-3;
• No evidence for a new variant of MMR-induced autism: Pediatrics 2001 Oct; 108(4):E58; 
• Autism and Measles, mumps, and rubella vaccine: no epidemiological evidence for a causal association. Lancet 1999 Jun 12;53(9169):2026-9; 
• MMR and autism: further evidence against a causal association. Vaccine 2001 Jun 14;19(27):3632-5.

I do not want to diminish the suffering of children with ASD. This is a real disorder, and it must be incredibly difficult for parents who have no clue what causes it. However, we can be nearly 100% sure that the MMR vaccine does NOT cause ASD (though it may cause other untoward side effects). However, not vaccinating your child will put the child at a greater risk of acquiring dangerous infections. In fact, vaccine coverage for MMR is excellent at this time, >90%. There are only 55 new cases of measles in the US every year. However, most of those are in children who were deliberately unimmunized by their parents, for whatever reason. That is where the problem lies....