Confirmation Bias and the Dangers of the Unvaccinated

If studies continuously debunk these ideas, why do people believe them? It's partly due to the David and Goliath factor -- with the maverick scientist versus Big Pharma/Big Government. When government organizations like the U.S. Food and Drug Administration are tied so closely to drugmakers, their answers (or lack thereof) can seem suspicious. The independent doctor working in his basement promising to find the cause and cure gives a reason to hope.

But there are unscrupulous people on both sides of the equation. The fact that someone is a regular Joe Schmo, albeit a Dr. Schmo, doesn't mean he or she is immune to the greedy impulses that influence the pharmaceutical companies. You can "follow the money" back to the drugmakers, but you can also follow it back to the lawyers and expert witnesses making a fortune in the Omnibus Autism Hearings and the people peddling expensive "remedies" such as chelation therapy, which removes toxic metals from the body.

It's easy to give in to confirmation bias, which occurs when you find facts that back up your beliefs and reject anything that might force you to reevaluate your stance. Many people also misunderstand correlation versus causation: Just because two events occurred near each other doesn't mean that one caused the other.

Let's say you bring your toddler in for a vaccination and shortly thereafter, your kid gets sick. You might think the vaccine led to his illness, but logically, that line of thought doesn't make sense. If you bought a strawberry ice cream cone with extra sprinkles and promptly tripped and skinned your knee, you wouldn't say that extra sprinkles cause clumsiness. But the very idea of vaccines is scary to some people -- it doesn't seem right to introduce disease in order to protect against it.

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New Yorkers queue up for their free smallpox vaccinations after 12 cases were reported in the state, April 1947.

­The dangers of the growing ranks of the unvaccinated are twofold. First, there's the very real prospect of an unvaccinated child or adult acquiring a disease. Before vaccines eradicated smallpox, it killed millions of people throughout history. According to the World Health Organization, the world saw 50 million cases of smallpox a year as late as the 1950s [source: WHO]. Those who didn't die were scarred for life or often blinded. And smallpox isn't the only vaccine success story. In 1952 in the United States, more than 57,000 people were struck with polio, which can cause paralysis and even death [source: CDC]. After Dr. Jonas Salk's vaccine became available, rates of infection dropped by 85 to 90 percent [source: CDC].

To compound the dangers of getting sick, vaccines also operate on a principle of herd immunity, or community immunity. Basically, the more people within a community who are vaccinated, the greater the chance we all have of fighting an outbreak of disease. Conversely, the more unvaccinated people, the greater the danger of falling prey to an epidemic. Before the measles vaccine became available in the '60s, 450 people died and 4,000 people developed encephalitis a year in the United States alone from a disease that we can now prevent [source: CDC].

And yet from January to July 2008, the Centers for Disease Control and Prevention received reports of 131 cases of measles, the highest number of cases since 1996 [source: CDC].

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