A recent study published in the “American Journal of Public Health” examined the demographics of California school students who had requested and received exemptions from mandatory vaccinations for nonmedical reasons. The study, “Sociodemographic Predictors of Vaccination Exemptions on the Basis of Personal Belief in California,” found that from 2007 to 2013 the rate of vaccine refusal for personal belief doubled, to 3.06 percent.

Though the rate of overall vaccine refusal was low in absolute terms, it has implications for what’s known as herd immunity and raises the risk of disease for the general population. The demographics of vaccine refusal reveal an interesting — and, for many, unexpected — pattern: despite overwhelming scientific evidence that vaccines are safe and effective, it's the more educated parents who tend to reject them.

Nicholas Bakalar of “The New York Times” notes that “Exemption percentages were generally higher in regions with higher income, higher levels of education, and predominantly white populations. In private schools, 5.43 percent of children were exempt, compared with 2.88 percent in public schools. In some suburban areas, rates of exemption were near 50 percent.”

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Part of the reason the anti-vaccination theme is so persistent is that it contains a strong conspiracy theory element. The belief is that the dangers and risks of vaccines are being intentionally hidden from the public by doctors and drug companies, in collusion with the government, for big profits. Joseph Uscinski and Joseph Parent, in their book “American Conspiracy Theories,” note that “Conspiracy theories about vaccines are partially to blame for decreased rates of vaccination and an increased incidence of disease.”

Doubts about the safety and efficacy of vaccines are not merely the domain of the conspiracy crowd but instead are occasionally spread by mainstream news media. Celebrities such as Jenny McCarthy, for example, have long raised concerns, and earlier this year one of Canada’s most respected newspapers, the “Toronto Star,” ran a front-page series of articles casting doubt on the safety of the Gardasil anti-HPV vaccine — until an outcry from doctors led to the newspaper retracting the story and its publisher saying “the paper failed the public in the way it presented its story.”

Such high-profile news stories highlighting vaccine dangers — whether eventually retracted or not — can and do influence the opinions of the educated middle and upper class.

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Andrea Kitta, an Associate Professor at East Carolina University explains in her book “Vaccinations and Public Concern in History:”

“There is a discrepancy between personal health care and public health care. Autonomy and personal rights are very important to society; and North American medical culture values the rights of patients. For patients, it is acceptable to undertake a treatment when ill, but it is harder to accept a preventative measure, especially when the person in question is not sick. Add to this the risk of a health individual being potentially harmed by a preventative measure, and there is no surprise that many will refuse this treatment.”

Even those who acknowledge the safety and efficacy of vaccines may oppose them for unrelated reasons. Kitta told Discovery News, “People who choose not to vaccinate truly believe their rights are being violated and believe they are in danger of further violation … Some people will now reject vaccines solely on the basis that they feel their rights are being violated — not because they necessarily oppose or are even uncertain about vaccination.”

In an interview with Lindsay Beyerstein on the “Point of Inquiry” podcast, Dr. Paul Offit, director of the Vaccine Education Center and chief of the Division of Infectious Diseases at Children’s Hospital in Philadelphia, believes that the educated and wealthy parents don’t vaccinate because “they don’t fear the disease. I think it’s that simple. I think in Southern California, you’re living this wealthy, upper middle class, upper-class environment. You’re eating well, you’re exercising. You don’t see this disease so you think this is not going to happen to me, until it happens to you. That’s the way it always works with these diseases.”

Whatever the basis for a given person’s opposition to vaccination, the refusals are likely to continue. Protests against vaccinations date back centuries, often opposed not just by the poorly educated but also by those of wealth and status. Until and unless their own children are afflicted by a vaccine-preventable disease, they are likely to keep up the fight.