Measles and the Inoculation Effect


I gave a talk at Illinois-Wesleyan earlier today about marketing, persuasion, and pseudoscience.

As part of the notes, I mentioned that I had heard recently, but wasn’t sure of the veracity, that the measles outbreaks that were getting so much skeptic attention, were being wrongly blamed on anti-vaxxers. A few hours later, my RSS feed produced this gem, Measles Outbreak Traced to Fully Vaccinated Patient for First Time.

Well, that’s terrifying.

…a fully vaccinated 22-year-old theater employee in New York City who developed the measles in 2011 was released without hospitalization or quarantine. But like Typhoid Mary, this patient turned out to be unwittingly contagious. Ultimately, she transmitted the measles to four other people, according to a recent report in Clinical Infectious Diseases that tracked symptoms in the 88 people with whom “Measles Mary” interacted while she was sick. Surprisingly, two of the secondary patients had been fully vaccinated. And although the other two had no record of receiving the vaccine, they both showed signs of previous measles exposure that should have conferred immunity.

Now I want to talk about the inoculation effect.

The phenomenon, which is the closest psychology can get to convincing me to never argue for any cause I believe in ever, holds something like this: if you give someone a weak argument and they are able to refute it, they will be more resistant to stronger and similar arguments in the future.

On the one hand, this can be great. Don’t want kids to smoke? Start them with some arguments made for smoking (it’s coooool! everybody’s doing it!) and ask them why they’re bad arguments. Late, when some swaggering teenager* offers them a cigarette and leans in to say that all the cool kids are doing it, those kids won’t have to come up with an argument on the spot–they’ll be more likely to decline. This makes intuitive sense–if you’ve already thought about reasons that make All the Cool Kids Are Doing It an awful argument for smoking, you don’t have to create them on the spot. Practice makes perfect and all that.

Except that the other side of this problem is scary. What happens if you have a social movement you care about (not that any of my readers do, or anything…) and people are making terrible arguments for your side?** Then you come along with a better argument…and it fails, because your audience is used to knocking down the bad arguments and doesn’t care to listen to you.

Something like this:

A: I’m pretty skeptical about global warming. I’m not sure it’s real.

B: Yeah, but last summer was really hot! Remember how many record-breaking heat waves we had? When we were growing up, can you imagine having to stay in to avoid the heat so often? Or having so many deaths during a heat wave?

A: Okay, but this winter was one of the coldest on record. In fact, it was record-breaking! It’s mid-April and things are just starting to warm up. This global warming stuff is stupid.

Poor, unwitting C, who comes along later: But [scientific consensus, climate data, ice caps, desolate-looking polar bears]

A: GLOBAL WARMING IS A MYTH!

Or perhaps, let’s take an example that’s closer to home. Say you blame anti-vaccine advocates for causing a measles outbreak. Say you have headlines like Thanks, Anti-Vaxxers. You Just Brought Back Measles in NYC, or Measles is spreading, and the anti-vaccine movement is the cause. Or even Thanks Anti-Vax Loons: The Return Of The Measles And The Backlash Against Jenny McCarthy. And then, imagine what would happen if it turned out that you were completely wrong, and vaccines or lack thereof didn’t cause measles, and suddenly a bunch of people might be less likely than ever to get vaccinated.

That would be scary, no?

*I dunno, this is how peer pressure was always portrayed to me. 

**…or, my personal fear, that you ARE the one with the unpersuasive arguments?

Comments

  1. DrJen says

    Yep. Reminds me of a previous group of stories blaming an outbreak on ‘anti-vaxxers’ when it was actually folks who had a religious objection. I don’t find that any better of a reason to not vaccinate, but I’d prefer the articles to be accurate. A good angle on the above story would be, what is the percentage of vaccinated vs unvaccinated people that the initial case was likely to have come across and the infection rate across each group. But the discussion gets too complicated for a headline pretty quickly.

  2. stever says

    Ugh. I had my measles about 60 years ago, before the vaccine. So now I’m probably susceptible. When I saw the headline, I thought it was a case of the virus mutating away from the vaccine, as influenza does every year or so.

  3. says

    That would be scary, no?

    It certainly would be, because that would mean there is an increased vaccine failure rate. That in turn would mean the virus had mutated, the vaccine has been changed and/or something is causing people to become less responsive to the vaccine. However, that doesn’t absolve people that refuse to have their children vaccinated, because that also is a known cause of increasing the number of susceptible and contagious people in the population, thus diminishing herd immunity. So really, the only way those who refuse to vaccinate aren’t the cause of these outbreaks, at least in part, is if they are a negligible part of the population.

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