Don’t expect a `Disneyland effect’
“So how about that Disneyland measles outbreak?” As a researcher who studies vaccine refusal, I’ve been asked this question a lot recently. More than 50 people have come down with measles after exposure at the iconic Southern California amusement park, and nationwide measles diagnoses exceeded 90 in the month of January alone. (For the record, that’s a lot of measles cases to see in one month in the US in recent years, although 2014 was also banner year for the virus.)
Last week a colleague posed a particularly compelling question: “Do you think we’ll see a ‘Disneyland effect’?” – meaning, could this widespread outbreak produce a backlash against vaccine refusal and thereby reduce rates of vaccine exemptions, “alternative” vaccine schedules, or opting out completely of recommended childhood immunizations.
Parents less likely to refuse vaccines now?
It’s reasonable to expect a Disneyland effect. After all, there was strong evidence of a “Katie Couric effect” on colon cancer screening rates after Ms. Couric underwent an on-air colonoscopy in 2000. Similarly, an “Angelina Jolie effect” on breast cancer screening rates for women with a family history followed Ms. Jolie’s disclosure of her double mastectomy in 2013.
Several features of the Disneyland measles outbreak are also conducive to moving the needle on parents’ beliefs and decisions about childhood immunization: First, the outbreak has high salience: news stories have run in major print and broadcast outlets almost daily, and the internet and blogosphere are packed with posts from all perspectives. If vaccine hesitancy and worries about the measles virus were just lurking in the back of your brain last month, they are top-of-mind now. The universality of Disneyland may make parents feel more vulnerable in a “this could happen to us” way—it’s no longer possible to imagine that measles outbreaks or high rates of vaccine refusal are happening in another state or another school community.
Second, the Disneyland outbreak could shift both the social norms around vaccine refusal and the framing of the importance of childhood immunization. In recent years, people arguing against the safety, efficacy, and necessity of vaccines have created a powerful social norm that validates vaccine refusal and privileges claims about vaccine-related harms. In the Disneyland outbreak coverage, we are seeing more stories framed from the perspective of the potential harms of measles: for example, the stress and financial burden associated with quarantining an exposed infant; or the request from a father of an immune-compromised child to keep unvaccinated children out of his son’s school. This could in theory produce more “something must be done about this” sentiment that could then lead, for example, to stricter state vaccine exemption laws.
Third, this recent outbreak very simply plays on inherent present bias—our tendency as humans to heavily discount future costs and benefits of a decision or behavior while overweighting current costs and benefits. For most parents, the benefits of vaccinating are intangible (we take an action so that something doesn’t happen), probabilistic (vaccines are not 100% effective, and the chances of being exposed to measles are small), and in the future. It’s reasonable to imagine why parents with any level of concern about vaccines might opt out. The Disneyland outbreak shifts this calculus by making the cost of not vaccinating very immediate and tangible, and might therefore lead to decreased refusal.
A prediction (and I hope I’m wrong)
Despite these prior effects and reasonable assumptions, I hereby predict no such Disneyland effect this time. While I would be delighted to be proven wrong, I think there are at least three reasons why we won’t see a lasting impact of the outbreak on exemption or refusal rates.
First, our attention span is limited. While the Disneyland outbreak is getting a lot of coverage now, this will likely last for only a few more news cycles. (Caveat to this point: If someone were to die of measles from this outbreak – which I decidedly hope does not happen – the salience and duration of the outbreak in the news cycle would both increase.)
Second, the parents whose vaccine beliefs and behaviors are most likely to be affected by this outbreak are the slightly hesitant and the undecided. We are not likely to see much shift in the more adamant, hard-core anti-vaccine folks. In one anecdote from a news article on the outbreak, a non-vaccinating parent in Los Angeles reported that “she hadn’t even been aware of the Disneyland outbreak because she refused on principle to follow the mainstream news media. But she was in no doubt, even without reading the coverage, that ‘they have skewed the facts in favor of trying to sell people more pharmaceuticals’”. The same facts about the outbreak that might convince a moderately hesitant parent to vaccinate will only reinforce previously-held beliefs in a strongly anti-vaccine parent.
In a terrific recent paper, Brendan Nyhan and colleagues demonstrated this effect in a study in which parents were exposed to information about the dangers of vaccine-preventable diseases and the lack of evidence for an MMR-autism link. This information actually reduced intention to vaccinate among parents with previously unfavorable views of vaccines. Similarly, images of sick children with vaccine-preventable diseases increased beliefs in an MMR-autism link. So, the people whose beliefs we would most want to change in response to the Disneyland outbreak are the least likely to be persuaded. Unfortunately, these beliefs and the vaccine-refusing behaviors that accompany them tend to cluster socially and spatially–and it is this very clustering that leads to outbreak “hot spots” where herd immunity is most compromised.
Finally, I am skeptical about a Disneyland effect because I have spent a lot of time looking for a similar effect in other recent, highly-publicized outbreaks (including a 2008 measles outbreak in San Diego, California) and have failed to find one. That doesn’t mean it won’t happen this time. I will continue to look for shifts in social norms, beliefs, and behaviors in response to vaccine-preventable disease outbreaks, and work towards developing interventions that reduce vaccine hesitancy and boost herd immunity in the population. Let’s not let any more trips to Disneyland be ruined by Mickey Mouse science.
Alison Buttenheim is an Assistant Professor in the University of Pennsylvania School of Nursing, a Senior Fellow of the Leonard Davis Institute and the Center for Public Health Initiatives, and Faculty Affiliate in the LDI Center for Health Incentives and Behavioral Economics