by Tom Snee

Infections and hospitalizations from COVID-19 are on the rise again as a result of the Delta variant, but millions of Americans are still hesitant to take a vaccine to protect them.

Unfortunately, this hesitancy makes it hard for epidemiologists, economists, and public health experts to forecast the virus’ impact because the drivers behind vaccination hesitancy are not well understood.

A Tippie College of Business researcher recently took a deeper look at people’s vaccination decisions. Associate Professor of Finance Richard Peter and his co-author, Christophe Courbage of the Geneva School of Business Administration, adapted a long-standing economic model of decision-making under uncertainty to include people’s resistance to a vaccine.

So far, he says it’s the only model that allows us to understand how uncertainty may impede the willingness of people to get the vaccine, a factor that has shown itself to be significant, with as many as 30 percent of American adults still unvaccinated despite the rise of COVID-19 variants.

Peter says the current vaccination rate was difficult to predict because most models of human behavior do not take into account the reasons that are driving peoples’ hesitancy to get the vaccine. Was it because they didn’t think the disease was a big deal? That they wouldn’t get infected? Did they think the vaccine was a bigger risk than the disease, or doubt its efficacy to prevent the disease?

If you don’t know those drivers, he says, it’s hard to change their minds. Their beliefs can be due to lack of information, limited trust in science and institutions, or a general skepticism. Oftentimes, peers can play an important role in the formation of individual beliefs.

 “Vaccination decisions are indeed personal decisions in the sense that people’s beliefs matter for what they decide to do,” he says. “These personal beliefs may or may not hold up against objective information but in the end, they are important drivers of individual behavior.”

The original model was designed in the 1990s and is used widely in finance and economics to help explain how people make decisions when faced with varying degrees of uncertainty. One of the main advantages of the model is that it allows researchers to incorporate people’s personal beliefs and make predictions about how these beliefs will affect behavior.

Peter says his modified model can be used to help design and evaluate strategies in the fight against COVID-19. For instance, he says public health experts could use the model to assess and compare potential communication strategies to encourage hesitant people to get the vaccine.

Peter started developing the model earlier this year and it was published just a few months later in the journal Health Economics, a turnaround he says is among the quickest he’s ever had. The model was published online August 4, 2021 for public health professionals, economists, and others who need to incorporate public resistance to vaccines into their forecasts and think systematically about its root causes.

CONTACT: Tom Snee, 319-384-0010 (o); 319-541-8434 (c); tom-snee@uiowa.edu