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May 3, 2007

Health Outlook: Vaccines, Part 2 — Dispelling fears and misconceptions

With new vaccines come new worries, along with the concerns about vaccines that have been around for some time. This week we address some of those concerns — namely, the purported link between autism and the MMR (measles, mumps and rubella) vaccine and the preservative thimerosal.

The MMR controversy began in 1998 when a European gastroenterologist named Wakefield described a series of 12 children with developmental regression and stomach problems. Nine of the 12 had been diagnosed with autism. Eight of the nine children’s parents reported the start of behavioral changes coinciding with the administration of the MMR vaccine at 12 to 15 months of age (which also happens to be the same age at which autistic behaviors tend to emerge.)

Wakefield theorized, but did not prove, that infection with the vaccine strain of the measles virus caused inflammation in the stomach, which allowed potential neurotoxins into the body. This one article, published in the British medical journal Lancet, caused a media frenzy. Immunization rates plummeted despite the fact that the authors never offered proof of their theory.

Since then, numerous scientific studies have failed to demonstrate a link between autism and the MMR vaccine. Some were large studies comparing rates of autism in vaccinated vs. unvaccinated children. Others noted an increase in the rates of diagnosis of autism without a similar increase in MMR administration. In Japan, where MMR vaccine coverage was suspended for a time, the rates of autistic spectrum disorders (ASD) continued to rise. One important recent study failed to detect persistent measles virus in autistic children who got their routine MMR vaccine.

The bottom line regarding the Wakefield report is that it was a very small study with very few children, which proposed a theory while offering no proof. Importantly, 10 of the 12 authors of that study have since published retractions of their findings. The Institute of Medicine has concluded that “the body of epidemiological evidence favors rejection of a causal relationship between the MMR vaccine and autism.”

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