We ran the field experiment in cooperation with a bank in Ecuador. This bank focuses on consumer credit and is one of the largest credit card issuers in the country. Its headquarters are in Quito, Ecuador’s capital, and it has six branches across the country with over 1,300 employees, distributed in 31 divisions with 142 working units. The bank had run small vaccination campaigns in the past. These campaigns included only some employees in crowded areas and ran during the workweek in the bank’s offices. In 2017, the bank decided to extend its annual campaign to all its employees and allowed us to experimentally modify it to investigate how to increase take-up and the effects of vaccination. We implemented three interventions: we changed the vaccine’s price for some employees using income-dependent subsidies, we randomized assignments for on-site vaccinations across weekdays, and we implemented information nudges by varying the content of the emails used to invite employees to vaccinate.
The bank decided to provide the vaccine for free to areas that participated in campaigns in previous years and to partially subsidize it for new participants. Since the company opposed the randomizing subsidies, we used information on employees’ income to allocate this subsidy. Employees who earned less than $750 per month would pay $4.95 to get vaccinated, while those who earned more than $750 would pay $7.43. Note that the vaccine’s full price is $9.99. Employees were informed about the vaccine’s price in their invitation email. This email included basic information about the campaign and informed employees that the payment for the vaccine was directly deducted from their paycheck if they opted to get vaccinated. The email also contained information on the assigned day and time.
To examine the effects of opportunity costs and information, we randomly assigned all employees into one of four groups. First, employees assigned to the control group (Control) were invited to get vaccinated during the workweek (Wednesday, Thursday, or Friday) and were allowed to take time off their duties to get vaccinated. The specific day was selected randomly for each employee.
The first treatment increased the opportunity costs of vaccination by assigning employees to get vaccinated on Saturday. The employees usually do not work during the weekend, so they would incur extra transportation costs and have to arrange their schedules to go to the bank and get vaccinated. Otherwise, this group received the same information as the Control. This treatment was only applied in Quito because all the other branches are substantially smaller (82% of the employees work in Quito), and their employees could get vaccinated in a single day, which was not possible in Quito.
We also implemented two information nudges. We kept the additional messages as unobtrusive as possible to prevent confounding the effect of information with salience or other behavioral factors. The first nudge highlights the social benefits of flu immunization (Altruistic Treatment). In addition to the information provided to the control group, the email included the phrase: “Getting vaccinated also protects people around you, including those who are more vulnerable to serious flu illness, like infants, young children, the elderly and people with serious health conditions that cannot get vaccinated.” The second nudge highlights the individual benefits of flu immunization (Selfish Treatment). In addition to the information provided to the control group, the email included the phrase: “Vaccination can significantly reduce your risk of getting sick, according to both health officials from the World Health Organization and numerous scientific studies.” Employees in these two treatments were assigned to get vaccinated during the workweek, while the specific day was selected randomly.