Face the Vaxx

Cognitive bias and the science of disbelief

by Anna Wermuth; illustrations by Charlotte Wall and Emma Kerr

Imagine being the parent of a five-year-old with childhood leukemia. You feel as though the attention you pay to your son’s happiness is more important than your career, your hobbies, or your personal goals. You strive for a balance between carefully managing his health and granting him the freedom to roam and dream. Communicating to him and to others in your life the implications of his cancer—not to mention fielding the sentiment of pity that inevitably comes your way—is a daily task that requires bravery and patience. No matter how much you worry about him, your greatest hope is that he enjoys each new day as it comes. 

When it’s time for him to start kindergarten, you prepare for it like any other parent, and he’s as thrilled as any kid would be. All goes as expected for the first two weeks. Then, quite suddenly, your son comes down with a 104° fever, a grating cough and inflamed eyes. These symptoms have nothing to do with his leukemia, and no one else in the family is sick. It takes his doctor quite some time to come up with an accurate diagnosis for such an unfamiliar combination of ailments. She is deeply concerned about the high fever in addition to his preexisting condition. 

Eventually, the culprit is discovered. This child and several others in the neighborhood have contracted a severely contagious, airborne microbe that can also be fatal: the measles virus. The CDC is unsure of the exact source of the outbreak, but it most certainly came from overseas, considering widespread immunization effectively eliminated measles from the United States at the turn of the millennium. Over time, they theorized that the particular viral strain was identical to the one that infected 58,010 people in the Philippines throughout 2014, killing 110. It’s predicted that several unprotected Americans breathed in the measles virus in December 2014 when they came into proximity with Filipino travellers at Disneyland in Orange County, Calif. Upon returning to their home cities, they infected hundreds of others who had never received the MMR (measles, mumps, rubella) vaccine.

As the weeks went by, the disease spread and caused a multi-state outbreak that made stark national headlines: “Rise in Measles Cases Marks a ‘Wake-Up Call’ for United States” (NPR, January 29, 2015); “Spreading Measles Outbreak Also Takes Heavy Economic Toll” (Scientific American, February 5, 2015). Fortunately, there was adequate treatment and few deaths. Of course, in countries without sufficient healthcare and medicine, the same cannot be said. In 2014, measles killed 114,900, tuberculosis killed 1.5 million and diarrheal rotaviruses killed 760,000 children under five across the globe. Each of these diseases is preventable through vaccination; it’s simply a matter of distribution, monitoring, and education. The United States has, for the most part, had success in eliminating these preventable diseases, which is why many Americans are so unfamiliar with measles.

A crucial principle in epidemiology, or the study of diseases and how they spread, is something called herd immunity. It requires that at least 90 percent of the population be vaccinated against any given disease in order to protect immune compromised individuals, whose bodies cannot tolerate vaccines, like children with leukemia or HIV/AIDS patients. This explains why our hypothetical five year old got sick. There were enough people who had chosen not to vaccinate their children that measles was able to spread in his community and infect him, as well, because his parents didn’t have the same preventative options available for him.

If vaccines save millions of lives each year, and if they’re accessible to U.S. citizens, why are so many people choosing not to get them? Even more perplexing, how did the notion become so popular? If you aren’t familiar with the anti-vaccine movement, you might be wondering what’s behind it. Why do people deliberately reject protection against potentially fatal bacterial and viral diseases?

The answer lies in the psychology of cultural cognition. A team of scholars at Yale University, including Psychology Professor Dan Kahan and Columbia School of Law student Maggie Wittlin, define cultural cognition as “the tendency of individuals to conform their beliefs about disputed matters of fact to values that define their cultural identities.” There is a long list of cognitive biases that lead to beliefs and influence how humans perceive the world around them. A certain handful of biases are especially relevant to individuals who oppose vaccination. Seth Mnookin, author of “The Panic Virus,” proposes that these mental frameworks “convince us that it is our feelings about a situation and not the facts that represent the truth.” Ironically, science can explain why so many American citizens don’t trust the science behind vaccines. 

Before addressing these well-understood psychological mechanisms, we must begin with something that science cannot yet explain: autism. Despite never-ending research, there is still no conclusive answer for what causes the range of neurological characteristics that define autism spectrum disorder (ASD). Leading hypotheses suggest a combination of environmental and genetic factors. Diagnoses of autism are on the rise, but many doctors believe this is because of better, more comprehensive diagnostic procedures, and not necessarily because of an increase in the incidences of autism. In spite of all this ambiguity, what is clear is that being a parent of a child with a developmental disorder is profoundly challenging. Autistic childrens’ tendencies toward aggression, extreme difficulty in communicating and repetitive behaviors can be overwhelming to say the least. Even more disheartening, many children develop autistic characteristics after they’ve shown promising signs of intelligence and positive development. All of a sudden, their cognitive growth comes to a halt, and parents seek a source of blame. 

In the late 1990s, a British man named Andrew Wakefield conducted an unethical, unprofessional research study hypothesizing a causal relationship between the MMR vaccine and autism. Specifically, he was investigating the use of thimerosal, a mercury-based preservative found in many vaccines. The results, published in 1998 in the medical journal Lancet, suggested that there was a direct link between autism diagnoses in children and the fact that they’d received the thimerosal-containing MMR vaccine. 

However, there is a crucial difference between correlation and causation—there must be measurable evidence to prove that one thing is directly leading to another, not just that a cause-and-effect relationship results from the coexistence of both. His claim that the MMR vaccine causes autism, without empirical data to connect the dots, is like saying that eating rye bread causes acne because some teenagers have had one too many loaves.  Also, thimerosal is not toxic to the body, and, if it were, it wouldn’t have been approved during vaccine clinical safety trials. In reality, one is exposed to more mercury in the natural environment—from seafood, radioactive decay, and the incineration of coal—than in all doses of recommended vaccinations combined.

The aforementioned flaws are not even the principal invalidations for Wakefield’s study—in other words, it gets worse. He and his co-researchers, along with the review board that allowed his article to be passed on for publication, engaged in extremely unethical practices. There is a video of Wakefield casually admitting to paying children at his son’s birthday party five pounds each (or about ten dollars) to line up and give him blood samples. Additionally, he failed to provide information regarding his sources of funding, one of which was a legal firm seeking litigation for clients with alleged reactions to the MMR vaccine. According to the National Institute of Health, “the disclosure that legal aid funding had paid for some of the clinical investigations in the Lancet paper led the journal to formally retract the study in 2004, citing a ‘fatal conflict of interest.’” In 2007, the United Kingdom’s General Medical Council revoked Andrew Wakefield’s medical license, accusing him of “bringing the medical profession into disrepute.” Tragically, the damage had already been done: One seditious study started an outburst that would spark fury and suspicion for years to come. Dozens of properly conducted research efforts have since investigated the highly contentious question of whether a relationship between vaccines and autism exist, and the evidence is clear: There isn’t one. Anti-vaccine proponents stand by their opinions nonetheless. 

Seth Mnookin writes, “Misguided, ill-informed, and cavalier coverage of science and medicine is not always so benign: It influences how hundreds of millions of research dollars are spent, it sucks up the time and energy of public health officials already stretched thin, and it bestows credibility on people’s delusions and fantasies, with occasionally calamitous results.” One could write an entirely separate article on poorly conducted scientific studies and their implications for society, or how the inappropriate communication of science research by the media has massive impacts on cultural cognition. The effects of the Wakefield study illustrate one of the main historical factors behind the current cognitive biases that motivate anti-vaxxers.

The first is called negativity bias. It is the human tendency to focus on negative outcomes rather than positive ones. For example, if you go to class one day and your laptop won’t turn on, you start to think of any explanation for what went wrong, whereas if it functioned normally you tend not to consider what went right. People have different “explanatory styles” to compensate for confusion. Some people blame themselves for negative outcomes while others blame larger forces beyond their control. It is quite common for a parent with an autistic child to feel guilty for their kid’s condition. Many more parents are prepared to accuse the federal government and the CDC. In the absence of a clear explanation for what actually causes ASD, a desperate mom or dad living in the age of the Internet will quickly encounter the fervent online community that tells emotional and convincing anecdotes about the link between vaccines and autism. Without the skepticism to reject the unsupported content they find, people frequently let anti-vaccine ideas catch on and take hold.

This brings us to confirmation bias. When someone encounters information that aligns with their previously held beliefs, they tend to readily confirm its validity, without scrutiny or doubt. Like negativity bias, everyone is prone to this kind of thinking. If we weren’t, we probably wouldn’t be able to formulate concrete worldviews, and would thereby lack tangible identities. Thus, when an individual has made up their mind about the cause of their child’s disability, they will easily accept newly presented stories and theories that support that opinion. 

Moreover, a person will become further convinced that they’re right about something if someone tries to prove them wrong. This phenomenon was first described by social psychologist Leon Festinger in his 1956 book, “When Prophecy Fails.” He says, “Suppose an individual believes something with his whole heart; suppose further that he has a commitment to this belief, that he has taken irrevocable actions because of it; finally, suppose that he is presented with evidence, unequivocal and undeniable evidence, that his belief is wrong; what will happen? The individual will frequently emerge, not only unshaken, but even more convinced of the truth of his beliefs than ever before. Indeed, he may show a new fervor about convincing and converting other people to his view.” This has an uncanny resemblance to the momentum of the anti-vaccine movement, but is applicable to all of us, once again. Notice how open or closed your mind is the next time someone tries to refute a belief you have held and acted upon for several years—chances are, even if you’re swayed by veritable facts, you’ll feel uneasy about the choices you’ve made, and will probably try to defend yourself for your own integrity’s sake. 

In the context of anti-vaxxers, the belief that vaccines lead to developmental disorders does not usually move people to action (unless you count picketing outside of the CDC). Rather, by avoiding immunization, parents are choosing not to act at all. This is because of the omission bias—a preference for mistakes that result from inaction rather than mistakes that result from action. A 2009 study led by doctors Katrina Brown and J. Simon Kroll out of London’s Imperial College surveyed 142 parents from the UK, asking about their perceptions on the likelihood, symptoms and duration of both a hypothetical disease and a vaccine adverse event (VAE), such as a rare allergic reaction. The data found that parents’ outlooks were more strongly averse to the possibility of a VAE than to the possibility of disease. The abstract of the study states, “This data suggest that any vaccine is at a disadvantage in many parents’ consciousness in comparison with the infection itself, and that minor safety concerns could have disproportionately detrimental effects on vaccine uptake.” Essentially, our ability to evaluate risk is pretty terrible, and the suggested effect has actually been documented: vaccine rates in the UK and in the U.S. have drastically declined. In the U.S., parents can be granted religious or philosophical vaccination exemptions for their children before they start school, in all but three states (California, Mississippi, and West Virginia). Herd immunity continues to go down, putting the very young, the elderly, and pregnant women at risk.

It is a distinctly Westernized privilege to choose not to vaccinate. People are generally unfamiliar with the negative implications of a decline in herd immunity because the diseases at hand have been incredibly uncommon in this country for generations. Paradoxically, that’s because of the tremendous success of vaccines. 

When something awful happens to someone we love—like when a child develops autism or suffers a rare allergic reaction—it is instinctual for human beings to search for a source of blame. The feelings of guilt commonly experienced by parents of children with developmental disorders may explain why many of them hastily attack large, powerful societal forces such as vaccine developers and branches of government to relocate their pain and confusion where concrete evidence for causation of autism has not yet been found. However, to suggest that the medical research community would purposefully inoculate the masses with more harm than benefit, through the medium of vaccines, is to propose that those people would do the same to themselves and their children. Senators, drug developers, doctors, and trained researchers are not immune to polio, measles or yellow fever. Bacteria and viruses couldn’t give a damn about the political or economic statuses of their families. Every treatment or surgery comes with risk factors, as does opting out of treatment altogether. With infectious disease, global public health is at stake. It’s clear that individual choices do not simply affect the individual.

Yet, in light of the psychology of cognitive bias, it’s hard to accuse anti-vaxxers of deliberate ill intent. In fact, considering that all human beings have their perceptions skewed by cognitive bias, this turns out to be a much more universal affliction. Hank Green, creator and co-host of the YouTube channel Sci Show, illuminates this in his video, “The Science of Anti-Vaccination.” He says, 

“This is not an ‘anti-vaxxer’ problem; it’s a human problem. Those of us who trust science, or have built an understanding of statistics and bias, simply have had different lives than people who more heavily weigh anecdotes or the opinions of their friends, or strangers they meet online who feel the same way. So next time you find yourself frustrated about the decline in vaccinations in America, remember that it’s only because of the dramatic success of vaccines that we could even think of having this debate, and that those anti-vaccine activists are being driven by the exact same logic traps and cognitive biases that every one of us suffers from. Only by understanding and accepting these psychological pitfalls that we’re all so susceptible to will we be able to solve this problem. And that’s what science is all about.”

Only careful adherence to the scientific method will provide the answers we seek—answers that will prevent HIV/AIDS, cure cancer, treat schizophrenia, and illuminate the cause(s) of autism spectrum disorder. It was the brave efforts of methodical scientists that brought vaccines into the world and ultimately improved it in immeasurable ways. Instead of passing harsh judgment onto people who oppose vaccination, it’s better to educate the public on the practical applications of science so that our lives and our children’s lives can benefit from its advances.