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Vaccines: Fact and Fiction

the worry: Vaccines cause autism

what's behind it: This claim first came to the forefront in 1998, after a British study linked the MMR vaccine to 12 children with autism. Prior to this, there had been some concern that thimerosal, a mercury-based preservative common in many vaccines at the time, also may have been partly or totally to blame for some cases of autism.

the facts: So far, ten studies involving thousands of children have failed to find any connection between the MMR and autism. Plus, the original paper suggesting a connec tion between the two was formally retracted by 10 of its 13 authors in 2004. As for the thimerosal issue, there's a bit more backstory worth explaining: First, it's absolutely true that mercury can be harmful. The kind in contaminated fish and water builds up in the body when ingested and can cause severe nerve damage. However, the type of mercury that's in thimerosal doesn't accumulate in the body. "It's never been linked to any adverse effect," says William Schaffner, M.D., professor of preventive medicine at Vanderbilt University Medical Center, in Nashville. Plus, autism rates have continued to rise even after drug companies voluntarily phased out the preservative from all vaccines given to kids (with the exception of some flu shots) in 2001. Clearly, we are far from understanding everything we need to about the range of autistic disorders. And that's why "the possible link between vaccines and autism has been taken very seriously," says Dr. Schuchat. "But at this point, after so many studies, it's safe to say these two hypotheses have been eliminated as possible causes."

the worry: Too many shots too soon is risky

what's behind it: Late last year, the parents of 9-year-old Hannah Poling won a lawsuit in which they claimed that their daughter's autism had been triggered by the five "catch-up" shots for nine diseases she received in one day. She got the injections in 2000, when she was 19 months old. The highly publicized case underscored fears -- also raised by actress Jenny McCarthy, who has a son she believes has recovered from autism -- that the practice of giving multiple vaccines at once is too much for a small child's body to handle.

the facts: Hannah Poling was born with a disorder that affects her mitochondria (the structures within cells that produce energy). And though the family won the settlement on the theory that this underlying vulnerability could have made her more susceptible to vaccine injury, there's actually no proof that she -- or any other child with mitochondrial disease -- was in fact at any increased risk, says neurologist John Shoffner, M.D., associate professor of biology at Georgia State University, in Atlanta, one of the doctors who diagnosed Hannah's disorder. "There is no evidence that the contents of vaccines are the cause of autism or mitochondrial disorders," he says. What's more, because even common illnesses like colds, the flu, and rotavirus can cause significant harm to these children, doctors strongly advise they receive all the recommended shots.

So what does all of this mean for parents of healthy kids? Not much -- getting more than one shot at a time isn't the huge physical stress it seems to be. Their immune systems handle a far greater challenge from everyday exposure to germs on shared toys, doorknobs, and the playroom floor. As Dr. Offit explains it: Think about the bugs that caused your child's last ear infection. Each single bacterium has 2,000 to 3,000 components that stimulate an immune response from the body. As those bacteria multiply, the challenge to the immune system increases exponentially. Your baby feels awful and likely has a high fever and lots of pain. The body pulls out the stops to fight it off. Now compare that to this: "The entire fourteen-shot course of childhood vaccinations contains only about 150 immunological components altogether," says Dr. Offit. This is about a tenth of the challenge posed by exposure to just one microscopic germ. What's more, the bacteria and viruses used in vaccines are either killed or altered, says Martin Myers, M.D., author of Do Vaccines Cause That?! There are just enough to induce immunity, but not enough to make someone sick -- and certainly not enough to overload the immune system of a healthy child. As with any medical intervention, side effects, including soreness, rashes, and fever, are possible, but most are mild and short-lived. In rare instances, some children experience fever-induced seizures following shots, but though these are frightening, they cause no permanent harm.

One common response to these concerns and the autism claims is to break up combination vaccines (which may contain up to five inoculations in one) or to spread them out. But that carries significant risks of its own. "Too often, an immunization delayed is an immunization missed," says Dr. Schaffner. "It's hard enough for parents to keep track." More troubling, during the gaps, kids are susceptible to catching serious diseases they could have been protected from. Vaccines are scheduled when they are for precise reasons: It's a balance between finding the time when the baby's immune system can respond and knowing when he's most in danger of catching the infection, says Dr. Schuchat. Give a shot late and a child is left unprotected at his most vulnerable time. (For help tracking your child's schedule, click here to download a free Vaccine Tracker.)

Robert Sears, M.D., author of The Vaccine Book: Making the Right Decision for Your Child, offers parents an alternative to the American Academy of Pediatrics schedule -- but he does so with Dr. Schuchat's concerns in mind. There are certain vaccines, including those that protect against meningitis, rotavi rus, and pertussis, that he does not recommend delaying for the same reason she gives. However, he willingly offers families the option of postponing hepatitis A and B as well as polio, mainly because these illnesses do not pose the same threat to infants as the others.