Behavioral Barriers:

Salience: Our attention is limited. Therefore, behavioral economics interventions carefully consider the moment when a message is delivered, the location in which it is delivered, and the content it emphasizes. In this context, parents are unsure when they should vaccinate their daughters against HPV and wait for the doctors to recommend vaccination. However, all the doctors interviewed reported limited time during appointments, and more urgent issues took priority over HPV. The absence of discussions and reminders leads parents to assume passive attitudes toward HPV vaccination. In general, there is a lack of moments of reflection, choice, and opportunity to take action on HPV vaccination for girls aged 9-17 in Bogotá.

Mental accounting: Mental accounting is our tendency to mentally sort our money into separate “accounts,” leading us to see money as less fungible than it is and affecting our spending behavior. The concept is usually applied to personal finances, but in this context we apply it to the use of time and activity.  In the case of children’s vaccines, although the vaccine is part of the full vaccination scheme, parents do not put the same amount of effort into vaccinating their daughters against HPV as for other vaccines deemed “more essential.” Evidence from our interviews indicates that parents mistakenly view vaccination as no longer a significant priority in children's health considerations after five years of age. 

Mistrust: Mistrust occurs when one party is unwilling to rely on the actions of another party in a future situation. Government support for the HPV vaccine has waxed and waned in the past, adding complexity to parents’ decision to vaccinate their daughters. Health professionals believe that a more explicit endorsement from the government would increase trust and make parents more likely to accept the vaccine recommendation. Parents interviewed in the diagnostic phase of our study expressed their desire for the government to take a more explicit stance on their support of HPV vaccinations.

Present bias: Present bias, associated with a preference for instant gratification, is the tendency to opt for a lesser benefit in the short term over a greater benefit in the longer term. Because immunity is not tangible, it is difficult to appreciate the benefits of vaccination in the short term. In addition, there is no immediate consequence for failing to receive the HPV vaccine; this stands in contrast to, for example, the requirement of certain immunizations for children 0-5 years in order to be admitted to school. It thus becomes easy to put off the decision about HPV vaccination to the future.

Behavioral Tools:

Priming:  Priming is a phenomenon in which exposure to one stimulus influences how a person responds to a subsequent stimulus. These stimuli are often conceptually related words or images. For example, a moment after a person sees the word “doctor,” she will be faster to recognize the word “nurse” than she will be to recognize an unrelated word because the medical concepts are closely associated in her mind. In this experiment, we used the word “cancer” in two treatments priming people to think about the negative consequences of not vaccinating their daughters. By making negative consequences salient, we tried to induce negative emotions associated with regret and worry.

Planning tools:  Planning tools are designed to help individuals make a concrete plan for taking action. They urge the individual to divide the objective (for example, going to a medical appointment) into a series of smaller, concrete tasks (leave work early, find a babysitter, postpone a weekly meeting, etc.), and thereby anticipate unexpected developments. These tools often require the individual to write down crucial information such as the date, time, and place. We decided to provide an interactive map that tells parents the route from their location to the closest vaccination site and added a call to action that invited them to use the map. Due to the lack of space in SMS messages, this seemed an appropriate way to help them make their plans concrete.

Anticipated emotions: Emotions of this type are not experienced directly but are instead expectations of how a person will feel once the consequences associated with a decision are experienced. To overcome the present bias in this intertemporal choice, where the actions taken today to vaccinate girls will only have an effect in the future, we exploit the power of anticipated regret and anticipated worry to close the gap between the present and the future, prompting parents to take action today.

Soft shame: Shame is a powerful behavior driver. However, it must be treated carefully to prevent causing unnecessary distress. We included a soft version of shame by showing a sad face emoticon after telling parents that their daughter does not have the HPV vaccine. In this way we let parents know that the Secretariat of Health in Bogota is aware of their daughter’s missing vaccine and disapproves of this failure to act.    

Intervention Design

The Behavioral Economics Group, in coordination with the Secretary of Health from Bogota, The Ministry of Health in Colombia, La Liga Colombiana Contra el Cáncer, the American Cancer Society, and Universidad del Rosario, implemented several SMS experiments designed to increase HPV vaccination rates in Colombia. All the experiments were implemented through a text message campaign (SMS), differing in the behavioral tool used to prepare the message. Our team decided on this channel because the Secretary of Health in Bogota has already launched several SMS campaigns in the past. In this summary, we will explain one of those experiments based on emotional content related to the consequences and (soft) shame of inaction.

Table 1. Message content by behavioral design tool

As Table 1 shows, this experiment included three treatments designed with emotional elements and three control groups. The pure control group did not receive any message. The policy control group received the "business as usual" message that the Secretariat of Health in Bogotá was using in communications with the target population. The experimental control group included fixed elements that were incorporated into every treatment. The fixed elements for this informational experiment were a customized greeting with the parent’s name, the Secretariat of Health’s signature, and a planning tool. The planning tool consisted of a call to action to find the nearest vaccination point and provided a link to an interactive map.

The interactive map included in the experimental control and the treatment groups was developed by the Secretariat of Health of Bogota and provides georeferenced information about all the vaccination points in the city. This allows parents to find information conveniently by interacting with the website and being able to select the address they would like to find a vaccination point close to (e.g., their home, work, daughter’s school.) With this experiment, we also use the power of emotions to bring the perception of consequences closer to the present and thus nudge parents to take action now.

Each behavioral treatment targeted parents of girls that had never been vaccinated against HPV in the past, and the objective was to help them vaccinate their daughters for the first time. The number of parents who participated in this experiment was around 34,506. Table 1 shows the message by behavioral design tool used to design each message.

The experiment consisted of sending a weekly text message to the target population’s parents over 8 weeks. The content of the message remained constant. The vaccination records of the Secretariat of Health are updated daily, and our team received them weekly. This allowed us to remove those parents who had already taken action before sending the subsequent message.

Challenges

This project had several challenges:

• Despite our team’s solid credentials, it took considerable effort to create rapport with government employees at the Secretariat of Health. Specifically, the Secretariat of Health’s ethics committee asked us to make significant revisions to our ethics materials, even though the project had already gone through the ethics committee at Universidad del Rosario
• Related to that, it was not easy or fast to get the data set from Secretariat of Health's records because it took time to synchronize our team’s needs with the data extraction from administrative records. 
• Another obstacle was that the proposed government’s partner agency could not send the text messages, so we had to find an alternative platform to send SMS. We used a platform that we had previously worked with (Altiria), and our team programmed and sent the SMS. The upside is that we gained control over the experiment. However, we lost the opportunity to train government officials on these interventions. 
• HPV vaccines ran out after week 4 of our intervention in some vaccination centers. We had to stop sending SMS and helped in the coordination between the Ministry of Health and the Secretariat of Health. They quickly responded, and we were able to resume the experiment after pausing it for ten days. 

Results

Results indicate that the SMS intervention increased first-time HPV vaccination rates in Bogotá. We found in this experiment the most impactful message of all of the experiments that we ran in Bogotá for the first dose.

• The most impactful treatment to increase first-time vaccinations was soft shame. This group had an average vaccination rate of 7.6%, representing a 37% difference compared to the control group (vaccination group average of 5.5%).
• Two other experiments were equally effective in nudging vaccination. First, the experimental control that included the call to action and the planning tool was statistically significant and represented a 28% difference compared to the control group. Second, but not less important, was the anticipated regret from the consequences of cancer without a vaccine.
• Interestingly, we found a weak effect of the message that primed worry, which resulted less impactful in magnitude than the policy control. We hypothesize that the weak effect was derived from the different intensity of the emotion that was used for the priming (worry vs. regret).  

Figure 1. Soft shame and anticipated regret were effective emotions for getting parents to vaccinate their daughters, as well as the interactive map planning tool

Policy implications

• We encourage governments to make information about vaccination sites accessible to parents. In Bogotá, it was beneficial for parents to have an interactive map to look up the closest vaccination point. If no interactive map exists in a municipality, a list of locations or maps might be helpful to parents.

We also encourage governments to leverage their administrative data on vaccination rates. It was very effective in this context to remind parents of their responsibility to vaccinate their children. This could have not been done without the level of detail of a well-kept vaccination database by the Secretariat of Health in Bogotá.