The Risk of Fear of Vaccines

I posted something on Facebook about the U.S. Vaccine Court denying claims of parents who said their kids’ autism was caused by vaccination. I suggested that the arguments over this supposed link are no longer really about the science of vaccines, which is far more settled than the science on, say, climate change.(The U.S. National Academies of Science meta analysis of dozens of studies is summarized at http://tiny.cc/o5X9X) I suggested that the fears of those who still argue for the link are better understood by the science of risk perception, which helps us see that the fears are real, and must be respected, but they're not really about the facts regarding vaccines.

Several risk perception factors are at work here. Those who refuse to acknowledge the overwhelming evidence that there is no link between autism and vaccines don’t trust the government and pharmaceutical industry, and mistrust fuels fear. Parents with autistic kids have so little control over their children’s fate, and lack of control fuels fears. And any risk to kids evokes more fear than the same risk to adults. These risk perception factors are real, as real as the evidence disproving the autism-vaccines link. So despite a mountain of such evidence, the fears persist, and fuel a rising doubt about vaccines in general. I observed that this Perception Gap between the fear and the facts is dangerous, not only for parents who choose not to vaccinate their kids, but for everyone else, since herd immunity is important to keep largely defunct diseases like measles from spreading again.

I got two replies. One suggested that sometimes the cure – vaccination - is worse than the disease. Maybe in some rare cases, but not with measles, and other common diseases against which fewer people are being vaccinated. The danger of those illnesses is greater than the risks of the vaccines, which in rare instances cause allergic reactions, but according to worldwide scientific consensus do not cause the things the fearful parents claim. The body of evidence disproving the connection between autism and vaccines is as clear as one can possibly hope for in science, passionate doubters notwithstanding. One persuasive piece of evidence is the fact that thimerosal, the supposedly dangerous preservative in the MMR vaccines, was removed years ago under pressure from worried parents (despite no medical evidence that it posed a risk), yet the number of cases of childhood autism continues to rise.

Yet a few concerned people continue to doubt the safety of the Measles/Mumps/Rubella (MMR) vaccine, and their passion has spread to a rising fear of all vaccines. 54% of American parents worry about vaccines having serious side effects on their kids, and one parent in eight has refused at least one vaccine their pediatrician has suggested. (The University of Michigan study is summarized at http://www.businessweek.com/lifestyle/content/healthday/636473.html) Herd immunity to measles has dropped so low in some places that measles cases are rising dramatically, and in a few tragic instances it's killing children again. In 2008 the U.S. had more measles cases than any year since 1996. (It’s even worse in the U.K., Germany, Switzerland and Israel, among other countries.)

There is another risk perception factor at work here too. Risk v. Benefit. Not long ago when measles and other childhood diseases were widespread, and lethal in hundreds of cases, the benefit of the vaccines outweighed their risk. Now the risk of the diseases has become so low that we only worry about the drugs. Curious. Because they’ve succeeded, we worry more about the vaccines than the diseases from which they are protecting our children.

The other note I got, from a thoughtful friend and father of an autistic child, was rife with mistrust of scientific findings that disagree with his beliefs. He focuses his mistrust on only one or two studies denying the vaccines-autism link, about which conflict of interest questions have been raised, but ignores hundreds more that find the same thing. He mistrusts government and pharmaceutical companies. As we all should, to a reasonable degree. This thoughtful friend says that if the science is that strong, it will stand up to scrutiny. It has, many times over, at least to those not seeing the issue through the perspectives of their fears. When is there enough evidence? Only when it agrees with what we want it to say? When is there enough evidence so that we don't automatically dismiss as untrustworthy anyone who provides an answer which conflicts with our fears?

This isn't about denigrating the real and passionate concerns of those whose fears don't match the mountain of evidence that says they're wrong. Trust matters. Control matters. Risks to kids will always evoke deep concerns. It makes sense that we're less worried about diseases that are mostly forgotten so the benefit side of vaccines is less obvious than the risk side of the tradeoff. In the context of risk perception psychology, these fears make sense.

Rather, this is about making healthy choices. Not just for our own children, but for our friends and neighbors and society at large as well. Decision making from the heart, no matter how right those passions feel, may lead us into greater danger. We need to find out what is causing the rise in autism. Focusing on the disproved link with vaccines diverts time and attention from potentially more telling lines of investigation. It fuels a growing public mistrust in science and government. Sometimes our worries, as valid as they are, can get so unreasonable that the Perception Gap becomes the greatest risk of all.

Autism, Vaccines, and the Affective Response to Risk

In February 1998 The Lancet published a small paper by A. J. Wakefield, et. al., which studied 12 autistic children and found no link between their autism and the fact that the kids had received the measles/mumps/rubella (MMR) vaccine. “We did not prove an association between measles, mumps, and rubella vaccine and the syndrome described” they wrote.

But at the news conference announcing the findings, the lead author, Dr. Andrew Wakefield, suggested such a link, setting off a firestorm of fear that has had profound consequences for public health around the world, even for the public’s fading faith in science itself. The formal retraction of the paper by The Lancet Tuesday gives us a chance to step back and consider why this profound disconnect between our fears and the facts occurred, and the consequences, so we might think more carefully about risks moving forward.

Scientists think of risk as something measurable, quantifiable. To them, more probable = worse. But to you and me risk is more than a number. The Cambridge Dictionary defines risk as “the possibility of something bad happening.” Bad to you, and bad to me, can be very different things, at different times, under different circumstances. To us, it’s not just the probability of the unwanted outcome. It’s the nature of the badness too.

Humans have a powerful, complex system that helps us detect and respond to the possibility that something bad might happen. Most of this risk perception goes on below cognition, powered by ancient brain wiring and chemistry, and patterns of information processing, that rely on a host of subtle affective cues which help our brains instantly gauge whether some sight or sound or smell, or idea or memory, holds potential danger. The system rests on a hair wire trigger set to react to potential threats instinctively, before the cognitive parts of our brain even have a chance to get the information and think it over. And in the ongoing risk response that follows, emotions and instinct continue to have the edge over reason and purely fact-based rationality. As Joseph LeDoux, a pioneer in the neuroscience of fear, wrote in The Emotional Brain, “…the wiring of the brain at this point in our evolutionary history is such that connections from the emotional systems to the cognitive systems are stronger than connection from the cognitive systems to the emotional systems.”

One of the affective cues that will set off this system is a risk to our kids. (Look at our excessive fear of child abductions.) Wakefield’s suggested link between MMR vaccines and autism certainly tapped that sensitivity, especially among parents with autistic kids who hope that knowing the cause might afford a cure.

Another cue is trust. If we trust the people and institutions that are supposed to protect us, we will be less afraid. If we mistrust them, the same warning signal will set off a stronger more protective risk response. In Europe, where Wakefield’s intimations about MMR vaccine took off, they came against a backdrop of Mad Cow disease, controversy over the safety of genetically modified foods, and several other issues that had already begun to shake public trust in science and the public health institutions of government. So since Wakefield, as scientists have tried to explain the overwhelming evidence that refutes the connection Wakefield suggested, the problem hasn’t been the evidence. It’s been lack of trust in the institutions that develop and deliver that evidence.

Lack of trust, and a threat to our kids, were just two of many affective factors that contributed to the response to Wakefield, parts of a survival system that relies on facts and feelings, cognition and instinct. We should be grateful to this system. It’s worked pretty well, so far. But a system that evolved to respond instinctively to threats like guys with clubs, and snakes, and the dark, and which still gives the edge to affective cues over hard facts, can serve us poorly when more complex modern risks like vaccines, or climate change, or mercury in seafood come along. Responding affectively to threats that aren’t as obvious, that require a little more analysis, which involve tradeoffs, can get us into trouble.

Vaccination rates in many places are down, in some places below the ‘herd immunity’ level necessary to keep an infectious disease from spreading. In many places, measles is staging a comeback (and in some places, it’s killing kids). Resistance to many other vaccines has also risen. Tens of millions of dollars has been spent researching what science already knew - and what indeed Wakefield’s paper actually reported - that the link between MMR vaccination and autism that so understandably evokes fear in parents of autistic kids, isn’t there. And the continuing controversy, fueled by a 24/7 “He Who Screams Loudest Wins” media age, feeds a growing mistrust in the scientific community that provides precisely the kind of expertise we don’t have as individuals, and which we need to figure these things out for us.

We can’t undo the affective risk response system. It’s deeply wired into us. But in the name of all our health, we need to understand it better, honestly recognize the harms it can do, and factor an appreciation for the dangers of how we react to risk into the choices we make, as individuals, and as a society. That way those choices will not only feel right, but stand a better chance of doing us the most good.