Vaccination against COVID-19, the long-awaited endgame to the pandemic that has claimed more than two million lives worldwide (as of this writing), is currently underway. But any vaccination effort is only as effective as people’s willingness to receive the vaccine.

Juliet Carlisle, associate professor of political science, studies public opinion and behavior. In 2018, amid anti-vaccine sentiment and following outbreaks of preventable diseases, she and her colleagues surveyed around 2,500 people to see how hypothetical case counts of a disease in their community would affect their willingness to be vaccinated. Case counts, as well as political views, influenced that willingness, and the lessons learned from their study, published in PLOS Medicine, can inform the ongoing COVID-19 vaccination effort. We spoke with Carlisle to learn more about the study.

You conducted this survey in 2018, in those long-ago pre-COVID days. What prompted the study?

My collaborators and I have worked on previous projects that help explain vaccine likelihood. The motivation of these projects was driven in part due to the general increase in vaccine skeptics and exemptions from routine childhood vaccine schedules and the uptick in once nearly-eradicated diseases, such as measles. Another motivation was the outbreak of newer diseases such as Zika and Ebola and how individuals might respond to a novel disease with varying rates of infection and illness and disease effects.

How did the survey work and what were the results? 

We fielded an online public opinion survey with an embedded experiment. The experiment presented respondents with one of seven hypothetical disease outbreaks, which was followed up with items asking individuals how they would respond in terms of willingness to vaccinate. We find that the risk of mortality (death) was associated with greater willingness to vaccinate in the presence of fewer case counts compared to the risk of morbidity (severity of illness). Likewise, older populations were more willing than younger, people with high incomes were more willing than all income levels, men were more willing than women, and our findings suggest a relationship between willingness to vaccinate and political ideology.

How did political ideology affect people’s attitudes about vaccination? 

We find something very interesting about the role of political ideology. As we expect, conservatives are less likely to express willingness to vaccinate relative to liberals. However, when risk is lowest, at zero local cases, self-identified moderates are similar to conservative and very conservative respondents. When risk is highest at 100 local cases, moderate respondents are similar to those at the liberal ends of the ideological spectrum. Therefore, political moderates exhibit a higher responsiveness to changes in risk.

What does this tell us about the way we perceive risk? 

It tells us, once again, that risk is shaped by our worldviews, values and political orientations. This is not a new finding. Despite objective risk associated with disease, political orientation filters how that risk is perceived. We see that with COVID-19: conservatives are shunning masks and lockdowns at higher rates than liberals. In part, it’s likely due to the perception of risk, but also is likely shaped by conservative opinion leaders who have downplayed the objective risk.

Did your study anticipate any aspects of the COVID-19 pandemic? 

In terms of the COVID-19 outbreak we have seen how political orientations are at play in terms of actual disease skepticism. In some ways, this is not completely surprising given the literature on the effects of opinion leadership. Additionally, although the vaccine is so new and there so far is limited research, our findings do seem to predict what we are seeing in terms of the ideological gap in willingness to be vaccinated for COVID-19. Recent polls support our findings that conservatives are less willing, liberals more willing and moderates shifting across time from their congruence with conservatives to their higher congruence with liberals.

Now that we have an approved vaccine, how can these findings help inform the rollout? 

In our other work, we find that trust of one’s primary care physicians is highest and therefore, primary care physicians likely have a big role in facilitating the vaccine roll-out. Moreover, conservative opinion leaders who publicly support the vaccine could also have a potentially positive impact in increasing willingness to vaccinate among conservatives.