Since 1998, when the British medical journal The Lancet published a study connecting the use of vaccines containing thimerosal, a mercury-based preservative, with a spike in the diagnoses of autism, a debate has waged over the validity of such a hypothesis. Since then, a number of other studies have been published, and the link between autism and vaccines has remained in the public eye. In fact, actress Jenny McCarthy recently came forward, claiming that her son, Evan, developed the disorder after receiving a measles-mumps-rubella (MMR) shot. Is the evidence that supports these facts well-founded, or is the development of autism in these children just sheer coincidence?


The Lowdown on Mercury
A recent University of Rochester study published in the February issue of Pediatrics showed that ethyl mercury, the type used in thimerosal, was quickly excreted among the infants who took part in the study, meaning that unlike methyl mercury, which is often found in fish, ethyl mercury cannot establish a progressive, debilitating buildup in the body. Additionally, investigations undertaken in Denmark and by the California Department of Health concluded that the removal of thimerosal from childhood vaccines failed to result in a corresponding decrease in autism; in fact, diagnoses of the disorder continued to rise in the preservative's absence. Still, many parents stand firm in the belief that their autistic children would have been fine had they not received certain vaccines.


Why the Increase in Autism?
If autism isn't undeniably the result of vaccines, why the increase in the reported incidences of the disorder? Experts credit heightened public awareness and the greater pool of knowledge available to the medical community. Understandably, this provides little solace to concerned parents, especially in light of plight of Hannah Poling, the subject of a federal court case last year. Soon after the girl received five vaccines in 2000, she developed a high fever and exhibited signs of lethargy and irritability that persisted for 10 days and continued to surface over the following months. Doctors determined that Poling had a preexisting mitochondrial disorder that was exacerbated by the vaccination, leading to a regressive encephalopathy, a disease that causes the deceleration of brain activity, with autistic features.


However, scientists caution that Poling's case is quite rare. Mitochondrial disease, a genetic disorder in which the mechanisms that convert sugar and oxygen into cellular energy fail to function, often because of a stressor like a high fever, occurs among a very small segment of the population-each year about 4,000 children with the condition are born in the United States. And the likelihood that it will result in autism is also rather low, though researchers are still investigating the relationship between the disorders. Ironically, the diseases prevented by the vaccines in question are proven triggers for mitochondrial problems.

The Parental Plan

According to experts, the best thing that parents can do for their children is keep a watchful eye over them and maintain an open dialogue with their pediatrician. Remaining on track with regularly scheduled immunizations is also important. According to the American Academy of Pediatrics, whooping cough has become a threat yet again. In 2005, more than 20,000 cases were reported and eight infants died during an outbreak in Texas. Childhood vaccinations, which since 2001 have been manufactured with little to no trace of thimerosal, are vital in the fight against diseases that have the potential to take thousands of lives.