Why are we so afraid of vaccines?

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Despite the official retraction of the 1998 Lancet study that suggested a connection between vaccines and autism, as of 2010, 1 in 4 U.S. parents still believed that vaccines cause autism.

This belief is often cited as part of the cause of rising rates of “philosophical exemptions” from vaccines among parents in the U.S. Twenty states allow “philosophical exemptions” for those who object to vaccination on the basis of personal, moral, or other beliefs. In recent years, rates of philosophical exemptions have increased, rates of vaccination of young children have decreased, and resulting infectious disease outbreaks among children have been observed in places such as California and Washington. In California, the rate of parents seeking philosophical exemptions rose from 0.5% in 1996 to 1.5% in 2007. Between 2008 and 2010 in California, the number of kindergarteners attending schools in which 20 or more children were intentionally unvaccinated nearly doubled from 1937 in 2008 to 3675 in 2010. Vaccination rates have also decreased all over Europe, resulting in measles and rubella outbreaks in France, Spain, Italy, Germany, Switzerland, Romania, Belgium, Denmark, and Turkey.

The current outbreak of about 1000 cases of measles in Swansea, Wales is a jarring example of the serious effects of vaccine scares. A little over a decade ago, there were only a handful of cases of measles in England and Wales, and the disease was considered effectively eliminated. Yet after Andrew Wakefield’s discredited study in 1998, measles vaccination rates plummeted, with the lowest levels occurring in 2003-2004. There is evidence that the outbreak may in part be due to parents’ responses to media reporting. There is evidence that medical scare stories affect health behavior in general, and the reporting on MMR has been subjected to a kind of “false balance,” conveying the sense that there is a legitimate and sizeable conflict in the medical community about the dangers of MMR when in reality those touting this “danger” represent a fringe minority.

It is easy to become mired in philosophical and ethical debates about who in these situations has the right to make these decisions. Should parents have the liberty to put their children and other children at risk of contracting often fatal vaccine-preventable diseases? Yet a more immediate question should be: what kinds of communication from doctors and public health officials could realistically assuage parents’ concerns about the risks associated with vaccination? In order to disabuse parents of unfounded notions about risks associated with vaccines, it is vital to understand how most people form perceptions of risk in the first place. Armed with a better understanding of public perceptions of risks associated with vaccination, doctors and public health officials can begin to craft communications strategies that specifically target these beliefs. In other words, we should be applying risk perception theory to the development of communications strategies to encourage vaccination of children.

In 1987, Paul Slovic published a landmark article in Science about how the public conceives of and responds to various risk factors. Slovic emphasized that lay people consistently understand risk differently than experts do. Experts tend to evaluate risk using quantitative measures such as morbidity and mortality rates. Yet the public may not understand risk this way. Qualitative risk characteristics, such as involuntary risks, or risks that originate from unknown or unfamiliar sources, may greatly influence the average person’s valuation of risk.

Risk perception theory may go a long way in explaining why some parents still insist that vaccines cause disorders such as autism in the face of abundant evidence to the contrary. Research into risk perception indicates that vaccines are an excellent candidate for being perceived as high-risk. There are several features of vaccines that align them with features considered high-risk by most people: man-made risks are much more frightening than natural risks; risks seem more threatening if their benefits are not immediately obvious, and the benefits of vaccines against diseases such as measles and mumps are not immediately obvious since the illnesses associated with these viruses—but not the viruses themselves– have largely been eliminated by vaccines; and a risk imposed by another body (the government in this case) will feel riskier than a voluntary risk. Research has shown that risk perception forms a central component of health behavior. This means that if parents view vaccines as high risk, they will often behave in accordance with these beliefs and choose not to vaccinate their children.

An interesting and not frequently addressed question about vaccine anxiety in the U.S. and Europe is how culture-bound these fears are. Can we find the same or similar fears of vaccines in low and middle-income countries? Cross-cultural comparisons might aid us in understanding the entire phenomenon better. Recent, tragic events have demonstrated resistance to foreign vaccine programs in Nigeria and Pakistan, spurred by the belief that vaccines were being used to sterilize Muslim children. In general, however, social resistance to vaccines and fear of vaccines causing illnesses such as autism is less common in low- and middle-income countries, in part because death from vaccine-preventable illnesses is more visible and desire for vaccines is therefore more immediate. There is, however, some evidence that confusion and fear of new vaccines, including doubts about their efficacy, does exist in some low- and middle-income countries. The examples of resistance to polio vaccination programs in Nigeria and Pakistan demonstrate a general belief, also held by many parents in the U.S., that vaccines contain harmful materials and that government officials are either not being appropriately forthcoming with this information or are deliberately covering it up. At the same time, anti-vaccine sentiments, although widespread, are often bound by culture and may even in some cases serve as a proxy for other culturally-based fears. These fears, heterogeneous as they are, are often constructed from local socially- and politically-informed concepts of risk rather than from close analysis of the actual risk data. This is an instance in which understanding how individuals conduct risk analysis might be more helpful than trying to present the actual evidence on the risks of vaccines over and over to a skeptical population. Yet even cross-cultural perspectives indicate that there is something fundamental about vaccines that can stir fear of diverse kinds in people. Although the content of these fears might differ, I would argue that the fundamental cause of fear is the same: vaccines, as man-made, unfamiliar substances injected into the body, are a classic candidate for high risk perception.

Understanding where the persistent fears of vaccination originate is the first step in effectively relinquishing them. Perhaps reminding people of other man-made inventions with crucial benefits would help assuage fears of the “unnatural” vaccine. Whether or not this particular strategy would help is an empirical question that merits urgent scientific enquiry. Isolating the precise elements that constitute irrational fears of vaccination is a vital component of designing effective public health campaigns to encourage parents to immunize their children against devastating illnesses.

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