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.”
Another recent vaccine “scare” involved thimerosal. Thimerosal has been used as a preservative in vaccines, eye solutions and other pharmaceutical products for decades. It contains trace amounts of ethyl mercury. Ethyl mercury is an organic mercury related to, but quite different from, methyl mercury, which is contained in contaminated fish such as tuna and swordfish.
Methyl mercury is a known neurotoxin that readily crosses the placenta and is known to cause brain damage. This is the reason for the proscription that children and pregnant women limit their consumption of certain types of seafood to two servings a week and avoid other types altogether.
Ethyl mercury, on the other hand, crosses into the brain less readily and is broken down and cleared by the body more quickly than methyl mercury.
Exposure to cumulative amounts of the trace thimerosal found in vaccines has never been proven to cause any adverse effects in children. In 2001, despite the risk of adverse effects being theoretical, the American Academy of Pediatrics and the United States Food and Drug Administration urged manufacturers to remove thimerosal from vaccines as a precautionary measure to maintain the public’s trust in the vaccine program. Currently only certain types of flu shots still contain thimerosal. All the rest of the vaccines in the currently recommended schedule are thimerosal-free.
Since the preservative was removed, numerous studies have failed to demonstrate a higher incidence of autism or ASD in children vaccinated with thimerosal-containing vaccine, compared with children vaccinated with the thimerosal-free version.
Other studies found that the rates of autism continue to rise even though thimerosal has been removed from childhood vaccines. Again, the Institute of Medicine concluded that the evidence favors rejection of a causal relationship between thimerosal-containing vaccines and autism.
Let’s keep this all in perspective. There has been a greater than 99 percent decrease in the reported incidence of measles since the measles vaccine was first licensed in 1963. But measles is still around and it is a nasty disease.
Acute encephalitis, which often results in permanent brain damage, occurs in 1 of every 1,000 measles cases; death occurs in 1 to 3 of every 1,000 here in the United States. The bottom line is that we all want what is best for our children. We all want to protect them from disease while keeping them safe from harm. At this point it seems clear to me that the benefits of vaccination outweigh any risks.
Dr. Carolyn Roy-Bornstein is a board-certified pediatrician with Merrimack Valley Child and Adolescent Health and Merrimack Valley Hospital. Her office is at Merrimack Health Center, 62 Brown St., adjacent to the hospital. She can be reached at 978-521-8108. Parents are invited to e-mail questions for future columns to CRoy.MVCAH@comcast.net.
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Health Outlook: Vaccines, Part 2 — Dispelling fears and misconceptions
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In this undated file photo released by ABC, Dick Clark hosts the New Year's eve special from New York's Times Square. Clark, the television host who helped bring rock `n' roll into the mainstream on "American Bandstand," has died. He was 82. Spokesman Paul Shefrin says Clark died but did not provide further details. Clark had continued performing even after he suffered a stroke in 2004 that affected his ability to speak and walk. (AP Photo/ABC, Donna Svennevik, File)
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