measles, HIV, brendan nyhan, and an obscure paper I wrote in 2002
Vox has a nice interview with Dartmouth political scientist Brendan Nyhan about vaccine skeptics. What can be done to convince them? Brendan does research on political beliefs and has shown that in experimental settings, people don’t like to change beliefs even when confronted with correct information. His experiments show that this is true not only for political beliefs, but also controversial health beliefs like believing in the vaccine-autism link.
But there was an additional section in the interview that I found extremely interesting. Nyhan notes that it is easier to be a vaccine skeptic when you don’t actually see a lot of disease: “… many of the diseases that vaccines prevent today are essentially invisible in the US. Vaccines are a victim of their own success here.” This reminded me of a 2002 paper I wrote on STD/HIV transmission. In a model worked out by Kirby Schroeder and myself about people proposing to have risky sex with each other, we wrote that the model has an unusual prediction. If people are proposing risky sex based on how often their friends are infected, you may get unexpected outbreaks of disease:
In the models we have presented, there is no replacement; the population is stable. If we allow for replacement, then we arrive at a novel prediction: as uninfected individuals the population (through birth, migration, etc.) and HIV+ individuals leave (through illness), the proportion of infected individuals will decrease. Once this proportion falls, prior beliefs about the proportion of infected individuals will fall, and if this new prior belief is low enough , then HIV- negative individuals will switch from protected to unprotected sex. The long-term effect of replacement in our model, then, is an oscillation of infection rates… There is some evidence that oscillations in infection rates do occur… An intriguing avenue for research would be to link these patterns in infection rates to the behavior depicted in our model.
In other words, if your model of the world assumes that people take risk based on the infection rates of their buddies, then it is entirely possible, even predictable, that you will see sudden spikes or outbreaks because people “let their guard down.” For HIV, as more people use condoms and other measures, people may engage in more risky sex because few of their friends are infected. For measles and other childhood infections, people who live in very safe places may feel free to deviate from the standard practices that create that safety in their first place. I don’t know how to make vaccine skeptics change their minds, but I do know that movements like vaccine skepticism are some what predictable and we can prepare for it.