Using behavioral science to encourage hesitant parents to vaccinate their children

The COVID-19 pandemic has dominated the news cycle for so long that it’s easy to forget there was a significant measles outbreak in 2019. Despite the accessibility of the measles-mumps-rubella (MMR) vaccine for children and the one-time status of the U.S. as a measles-free country, the growing trend toward vaccine hesitancy has also led to outbreaks of previously managed conditions.

As healthcare providers and public health officials consider ways to change both minds and behaviors, we have been looking for answers about the most effective methods to do this using behavioral science. In 2021, we ran a global vaccine hesitancy study to learn how behavioral science approaches could encourage vaccine-hesitant and anti-vaccine adults to get the COVID-19 vaccine and standard adult vaccines (including shingles, human papilloma virus and pneumococcal). We also worked with vaccine-hesitant parents to learn which nudges worked to encourage them to vaccinate their children to help them build immunity against illnesses including rotavirus, measles, mumps and rubella. Through this comprehensive study, we surveyed more than 4,400 adults in the U.S., Canada, France, Germany, Italy, Japan and the U.K.

For the arm of the study we’re diving into here, we tested parents to better understand the subconscious biases that influence their decisions to allow their children to receive common pediatric vaccines.

While data indicates that the risk of severe COVID-19 symptoms may be lower for children than adults, there are still some unfortunate cases of young people experiencing long-term illness or death. Children also carry and spread the virus, prolonging the pandemic and putting adults in their family or social circles at risk.

The results of all of our vaccination hesitancy studies point to an important insight: The strategies that worked to persuade someone to vaccinate themselves are not the same as the strategies that would make these individuals comfortable vaccinating their children. We tested the same nudges on adults to learn whether they’d change their mind about receiving a COVID-19 vaccination as we did on parents as they consider giving their children pediatric vaccines, and only one nudge worked for both scenarios.

In the spring of 2021, we surveyed 1,800 parents in the U.S., Canada, France, Germany, Italy, Japan and the U.K. These participants identified themselves as being either vaccine-hesitant or anti-vaccine (i.e., they refuse to receive any type of vaccine). They represented a mix of age, race, gender, geographies, employment statuses and income levels.

More than a third of those who participated in the pediatric vaccine study told us they fear giving their child too many vaccines too quickly and they are afraid of the ingredients in common pediatric vaccines. Getting appointments for childhood vaccinations was not a barrier, according to 87% of respondents. Two top reasons why all hesitant individuals across countries did not want to immunize their children were concern over the risk of side effects and a lack of information about the vaccines. 

For the pediatric vaccine hesitancy study, we tested 14 different biases and found that more than a third of the participants were moved to vaccinate their children by five biases (see figure 1). When we looked at responses by country, we found that the Canadian market, at 42%, showed the most potential to be moved to change, with 29% of this effect attributed to the Social Norms nudge. Canada was closely followed by the populations in Japan (40%), Germany (37%) and Italy (37%). We saw the lowest movement in the U.S. and the U.K. at 35%. 

Let’s break down a few of the insights we learned from each successful test.

1. Social Norms: People believe that common social norms are good behaviors that they should follow. Although this was a successful intervention, it was most likely to motivate the pediatric-vaccine-hesitant in Germany and least likely in Italy, the U.K and the U.S. We also learned that parents who are employed full-time are more likely to allow their child to receive a vaccine once they perceive it to be a social norm.
   
   Bias test methodology
   Respondents were told that their community had effectively achieved herd immunity (i.e., 93% of children in their community had already been vaccinated against all common pediatric diseases).
   
   Percent change in behavior globally for Social Norms Bias: +24%
   
   Insights to apply
   According to our research, it will be more effective to frame general vaccines as “something most people do” rather than something that is “healthy for you” or “good for everyone.”​ Connecting norms with local groups, such as by ZIP code, workplace or age may enhance the impact of this effect.
   
2. Commitment Bias: When people state a commitment publicly or verbally, they are more likely to keep it. We found that this bias was most effective among populations in Japan and Canada. For parents who are employed full time, keeping a public commitment (such as what is required for their child attending their local school) outweighs their vaccine-hesitancy.
   
   Bias test methodology
   Respondents were told that a school their child was enrolled in requires them to receive a standard set of pediatric vaccines in order to attend, and that they had already told others their child would be attending that school (i.e., they made a public commitment).
   
   Percent change in behavior globally for Commitment Bias: +21%
   
   Insights to apply
   Workplace or community incentives and media messaging can establish that having your children vaccinated is a public norm, or to ask when parents intend to immunize their children. Community leaders, workplaces and doctors can also nudge people to make a verbal agreement to commit to having their children receive standard pediatric vaccines at scheduled times. Another effective practice may be social media initiatives that reward parents for keeping their children up to date with their standard vaccines.
   
3. In-Group Bias: In our experiments, respondents who self-identified as Black, Latin or Asian were told that those who identify as the same ethnicity as the respondent were over-represented in vaccine clinical trials after advocacy from community leaders. We found that when people feel that others who are like them are represented in clinical trials for a vaccine, they feel more comfortable allowing their child to receive that vaccine. This was especially true for participants who identified as Latin and for women who live in North America.
   
   Bias test methodology
   Respondents were asked to consider how much they trust information about their community or group being included in vaccine trials that comes from community advocates (i.e., in-groups).
   
   Percent change in behavior globally for In-Group Bias: +10%
   
   Insights to apply ​
   When reaching out to specific populations or ethnicities, focus on finding spokespeople or representatives from those groups who are willing to visibly promote pro-vaccine messages to start changing perceptions about vaccine acceptance. Communications should feature a diverse group of people across ethnicities and socioeconomic levels so that parents recognize that individuals who they can relate to are vaccinating their children against COVID-19 and childhood illnesses.
   
4. Confirmation Bias: Forcing people to take another person’s perspective can break confirmatory thinking about pediatric vaccines. This bias was most effective among parents with children aged two months to two years, parents living in cities and Asian parents living in North America.
   
   Bias test methodology
   Respondents were asked to consider why other parents might choose to vaccinate their children.
   
   Percent change in behavior globally for Confirmation Bias: +17%
   
   Insights to apply
   Where possible, develop a messaging campaign that encourages perspective-taking to de-bias what the individual thinks they have confirmed already. You can create worksheets or digital quizzes to encourage hesitant people to ask themselves why others would have their children vaccinated. Another approach is to tell stories or find testimonials with surprise endings, such as those who are anti-vaccine and who decided to have their children receive pediatric vaccines. All of these steps can help reduce confirmation bias in vaccine-hesitant populations.
   
5. Effort Bias: Making it seem easy to research pediatric vaccines may make parents more likely to make sure their child is immunized.
   
   Bias test methodology
   Respondents were told that their doctor gave them a pamphlet with information on each childhood vaccine, including the pros and cons of receiving each.
   
   Percent change in behavior globally for Effort Bias: +19%
   
   Insights to apply
   By providing clarity on vaccination processes and offering support programs, you can mitigate the perceived effort it takes to get pediatric vaccines. Another way to reduce perceived effort for vaccine-hesitant parents is to emphasize in messaging the greater effort and inconvenience it will require to care for a sick child.
   

Not only did we find that certain approaches did not work to encourage parents, two tactics actually had the effect of further discouraging these individuals from allowing their children to receive standard pediatric vaccines.

• Increased hesitation – Licensing Effect: In this bias, people balance out their “immoral” and “moral” behaviors. Prompting people to remember behaviors that made them feel guilty creates significantly less urgency to get their child vaccinated.
  
• Increased hesitation – Hyperbolic Discounting: This bias assumes that people will overvalue near-term rewards at the expense of long-term benefits. But we found that participants were no more likely to give their child a pediatric vaccine when they feel the effort is deferred instead of required immediately. Creating a system that sets up vaccine appointments at a future date or emphasizes how a little effort now will pay off in future benefits actually discourages parents from vaccinating their children. 
  

Although our study focused on encouraging vaccine-hesitant and anti-vaccine parents to give their children standard pediatric vaccines, it’s worth exploring whether some of the same bias triggers work to encourage hesitant parents to give their children the COVID-19 vaccine. Of the 19 different cognitive bias triggers we tested across adult COVID-19 vaccination hesitancy and pediatric vaccinations, confirmation bias and effort bias motivated both groups to change their minds.

Healthcare and public health officials should consider using various biases in parallel. When used together, for example, the top five biases moved 36% of respondents to agree to give their children pediatric vaccines. As countries around the world struggle to contain not only the pandemic, but also preventable conditions that had previously been wiped out by the use of vaccines, it’s time to lean on behavioral science to build data-based strategies around the steps that actually work to change minds.