Nudging Vaccination in Latin America: Insights from Three Field Experiments in Behavioral Economics

Deborah Martinez Villarreal

Major Professor: Thomas Stratmann, PhD, Department of Economics

Committee Members: Daniel E. Houser, Tyler Cowen

Vernon Smith Hall (formerly Metropolitan Building), #5075
April 27, 2023, 10:00 AM to 11:00 AM


In this dissertation, I address the impact of various principles of behavioral economics on vaccination rates and attitudes toward vaccines in Latin America with an experimental economics methodology. Each experiment was implemented with government entities in the respective study locations. With the insights generated by these studies, I seek to provide evidence-based recommendations to aid governments in optimizing resource allocation toward effective health promotion.

In chapter 1, I test the effect of norm nudges on increasing HPV vaccinations in Bogota, Colombia. In Bogota, only a minority of the population engages HPV vaccination. Norm nudges provide social information describing the prevalence of a behavior and/or its degree of social approval. I use a text message campaign to target parents with daughters between 9 and 17 years who need the first dose of the HPV vaccine. I compare five norm nudges, a control group, an experimental control group, and a policy control group. Two norm nudges contain social information communicating how other people’s behavior is changing over time, i.e., dynamic norm nudges. The results are based on actual HPV vaccinations from administrative data from the Secretariat of Health in Bogota. The results find that the trending norm, one of the two dynamic designs, increases average vaccination by 1.39 percent compared to the control group vaccination rate of 5.57 percent. It represents a difference in HPV vaccination rate equivalent to 25 percent compared to the control group. This effect is statistically significant at the 95 percent confidence level and robust to different specifications. This study contributes to the growing literature on the applications of dynamic norm nudges on behavior change.

In chapter 2, I examine the effectiveness of dynamic norm nudges on increasing second-dose HPV vaccinations for trendsetters. I follow the definition of trendsetters by Bicchieri and Funcke (2018). They define trendsetters as the initiators of norm abandonment. In this context, trendsetters are parents from the minority who vaccinated their daughters with the first-dose HPV vaccine between 2017-2020. The results are based on actual HPV vaccinations from administrative data from the Secretariat of Health in Bogota. The paper tests three variations of dynamic norm nudges that include trending norms, qualitative dynamic norms, and quantitative dynamic norms. Contrary to chapter one, the results indicate that dynamic norms do not increase second-dose HPV vaccination rates of trendsetters. However, injunctive norms have a statistically significant marginal increase in second-dose HPV vaccinations of 5.22 percent compared to the control average of 15.2 percent. This difference is equivalent to a 34 percent difference. The study contributes to the literature on the effect of norm nudges on minority behaviors and identifies the elements that make dynamic norm nudges effective in this context. In addition, the study contributes to the literature on the specific conditions under which norm nudges are effective.

In chapter 3, I estimate the effect of an online intervention based on the behavioral economics components of gamification, altruism, heuristics, and framing on COVID-19 vaccine attitudes. The innovation of this study is the intervention design that aims to overcome the limitations of information-based public health campaigns. On the one hand, it assumes limited attention and cognitive resources that bind the effectiveness of information-based interventions. Instead, I use the aforementioned behavioral economics components. On the other, instead of communicating facts about the safety and efficacy of COVID-19 vaccines, I use the online intervention to bring saliency to the risks of COVID-19. This is based on the World Health Organization (WHO) Strategic Advisory Group’s (SAGE) definition of vaccine hesitancy, which identifies complacency towards a given disease as one of the three factors that drive it. This is a field experiment conducted with the government of Guanajuato, Mexico, through a communications campaign. The online intervention improves vaccine attitudes on average by 2.6 percentage points. Moreover, I find that females, young adults (less than 24 years of age), and people with low levels of education have worse attitudes toward COVID-19 vaccines than other segments of the population.