Vaccine War

"Scientifically, I think the matter is settled," says Anders Hviid, an epidemiologist at the Statens Serum Institut in Denmark. In one of the largest and most comprehensive epidemiological studies available, Hviid and colleagues analysed data on more than a half million children and found no link between the MMR "triple shot" for measles, mumps and rubella and an increased rate of autism - a link that's been strongly asserted for years by anti-vaccine activists. Similar epidemiological studies in Denmark also failed to reveal a link between the mercury preservative thimerosal and autism. In fact, around the world, peer-reviewed epidemiological studies have found no link between autism and either the MMR shot or thimerosal.

But vaccine skeptics like celebrity Jenny McCarthy, whose son, Evan, was diagnosed with autism following a series of vaccinations, including MMR, are convinced that further study into the other 15 pediatric vaccines and their additives will ultimately reveal a link. "Something happened. And when I say something, I mean a behaviour, a trigger," McCarthy says. "Is it mercury? Is it the schedule? Is there just too many? My answer to people and what I've been telling them is, 'It's all of the above.' We don't know for sure, which is why we keep saying, 'Study it.'"

Further vaccine safety research is what businessman J.B. Handley, who founded the autism support group Generation Rescue, has been calling for, too. Handley says he has little doubt that vaccines are responsible. "There is no real-world study that shows me that those six vaccines didn't cause my son's autism."

Nowhere has the vaccine war grown more heated than in Ashland, Oregon - an area that is of high concern to the Centers for Disease Control and Prevention. With an estimated quarter of the town's children entering kindergarten not fully immunised, Ashland is one of the least vaccinated places in America.

Despite the best efforts of local pediatricians like Dr Donna Bradshaw-Walters, many parents are simply not convinced that vaccines do more good than harm, and they've been using Oregon's religious and personal-belief exemption to get out of the state vaccine mandate. "I think a child's immune system is so immature," says Jennifer Margulis, an Ashland writer and mother of four. Margulis decided against following the recommended CDC schedule - although prior to a trip to Africa she did have her children vaccinated for yellow fever, tetanus, polio and meningitis. Says Margulis, "If you read the list of ingredients about what you're putting intramuscularly into your child, it's scary."

According to public health workers, however, Margulis' decision puts the entire community at risk. Vaccines don't work for everyone, and in some kids the effects wear off, so it's only when everyone - or almost everyone - is immunised that "herd immunity" is effective. "There are hundreds of thousands of people in this country who cannot be vaccinated," says Dr Paul Offit, the chief of the Division of Infectious Diseases at The Children's Hospital of Philadelphia and the inventor of a vaccine for rotavirus. "They're getting chemotherapy for their cancers, or they're getting immunosuppressive therapy. They depend on those around them to be vaccinated."

Bioethicist Art Caplan argues that society has the right to coerce its parents to vaccinate their children even if vaccines carry a small risk: "Parents don't have unlimited rights with respect to the welfare of their children. You can't kill them. You can't put them at risk of fatal disease. You can't put them at risk of devastating disability."

Surveys reveal that America's conversation about vaccines is complex, involving not only medical risks and benefits but also ideological beliefs about parental choice and the limits of government. "This is true even of individuals who see the benefits of vaccines as substantial," political scientist Hank Jenkins-Smith says. "They still want it to be a choice. They don't want it to be compulsory."

Government control over individual choice is another factor fuelling the anti-vaccine backlash, despite the peer-reviewed science that vaccines are safe.

"People now have a way to get the information they couldn't before, to communicate it to other people, and to have a robust public debate that is not controlled by money or political power or by government policy," says Barbara Loe Fisher, president of the National Vaccine Information Center. "Physicians are going to have to get over the idea that they tell people what to do, and people are going to do it without questioning."