The fact is, none of us really think about risks in a scientific way. The things that make us afraid aren’t the most threatening dangers. But there are certain rules of thumb about the kinds of things we tend to fear. We are more afraid of insidious, unseeable and rare dangers than the obvious ones. You’re more likely to drown in a bathtub than get eaten by a shark, but it’s the shark that lurks beneath the surface. Avian flu is no threat compared to hospital infections, but routine staph infections don’t breed in chickens in the mysterious Far East. Lack of control also breeds fear, which helps explain why people generally feel safer talking on a cell phone while speeding down a rush-hour freeway than they do sitting with tray tables in an upright and locked position on a commercial airliner. And we’re more likely to worry about chronic diseases like cancer and polio, which strike unpredictably and last for years, than the quick, deadly ones like pneumonia and heart attack. We are especially afraid of ailments caused by socially illicit acts or that produce strange behaviors–syphilis, schizophrenia, AIDS–or whose causes are unknown–think autism. Vaccines are especially likely to provoke irrational fear. You’re sticking a needle into a healthy baby, after all. Babies get sick, often, and they cry all the time. There’s a great likelihood that a baby will get sick sometime soon after getting a vaccination. When you get sick after a meal in a restaurant, you tend not to go back to that establishment–even if that steak you ate was well-cooked. Likewise, people whose kids got ill after a vaccine are likely to link the two. This helps explain the great appeal of the vaccines-cause-autism theory.
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The problem with the growing number of vaccine skeptics in the U.S. is this: a single parent may make a calculated risk not to vaccinate their child, and escape unscathed. After all, polio is pretty much vanquished around the world, measles is rare in the United States, and whooping cough doesn't usually kill your kids, though it may make them very sick. But if too many parents who know better make the decision not to vaccinate, it will poke holes in the network of protection that decades of vaccination have built up in this country through herd immunity–the more people who are vaccinated, the safer our "herd," as the germs find fewer bodies in which to grow and spread. Considering the amount of dedicated time and effort that have gone into this lifesaving measure, that would be a terrible thing. So listen to your pediatrician's advice. Unless you have a really good reason not to, vaccinate.
http://vaccinethebook.typepad.com/mt/2006/12/how_to_think_ab.htmlIt's not surprising at all that parents prone to antivaccination beliefs have family histories of illness or an interest in alternative medicine such as homeopathy, as much of "alternative medicine" is hostile to vaccination. It's also quite common for religious beliefs to play a role. However, I would quibble somewhat with whether that apparent "sophisticated" understanding of the issues involved is actually as sophisticated as it appears on the surface. In some cases it may be, but far more often it's a superficial understanding that has little depth, mainly because few lay people have the detailed scientific and medical background to apply the information. It's often a matter of knowing facts, but not having the scientific experience, understanding of mechanisms, or sophistication to put them in context or to apply them to the situation properly, giving the veneer of scientific sophistication. I can't remember how many times that, while "debating" in misc.health.alternative, I would have a study quoted to me as supporting an antivaccination or other alternative medicine viewpoint and find that, when I actually took the trouble to look up the study and download the PDF of the actual article rather than just reading the abstract (which is all most lay people have access to and therefore all they read), I would find a far more nuanced and reasonable point or even that the article didn't support what the altie was saying. One other aspect that often comes into play is an extreme distrust of conventional medicine and/or the government such that few individual studies that question the safety of vaccines are given far more weight in their minds than the many more studies that show vaccines to be extraordinarily safe or large metanalyses (such as those done by the Cochrane Collaboration). Certainly this is one reason why the infamous Wakefield study, despite being shoddily designed and now thoroughly discredited, keeps rearing its ugly head again and again and continues to be cited by antivaccination activists as strong evidence that the MMR vaccine causes autism.
It's not surprising, too, that parents would place more value on whether vaccination benefits their children over the benefits to society through herd immunity. After all, a mother's and father's primary duty is to their own child, not other children. Part of the problem here is likely a matter of vaccination being a victim of its own success. Before, a one or two in a million risk of serious adverse reactions wasn't even blinked at because the diseases vaccines were designed to prevent were common and feared, so much so that it was an no-brainer to consider the risk of vaccination to be acceptable compared to the risk of disease. Now that major vaccine-preventable diseases have been largely controlled or eradicated, the benefit of vaccines in keeping disease at bay is no longer readily apparent in the daily experience of parents, leading to a situation where even the very small risk of serious adverse events from vaccination seems too high for a benefit that that parents cannot see for themselves. Also, parents tend not to understand that their participating in producing a larger pool of unvaccinated children endangers not only other children (both vaccinated and unvaccinated because no vaccine is 100% effective), but their own children, because, as vaccination rates fall, the diseases vaccinated against almost inevitably return.
http://scienceblogs.com/insolence/2007/01/the_sociology_of_the_antivaccination.php