Texting patients to get a flu shot increased vaccination rates — but some messages worked better than others

By Beth Newhart
May 6, 2021
Setting up lunch dates aren't the best use for text messages anymore. (Pexels/Tim Samuel)

Setting up lunch dates aren't the best use for text messages anymore. (Pexels/Tim Samuel)

Researchers with the University of Pennsylvania's Behavior Change for Good Initiative sent "text-based nudges" to patients with primary care doctor's appointments reminding them to get a flu shot, leading to increased vaccination rates and lending support to a similar texting system for similar interventions, including COVID-19 vaccines.

As explained in an April 29 paper published in the Proceedings of the National Academy of Sciences, the team's 19 text interventions used different strategies to convince people to get a flu shot at their next routine appointment. The messages were sent to more than 47,000 adult patients within the Penn Medicine and Geisinger Health systems in the northeastern U.S., incorporated with their regular text-based appointment reminders. There was also a control condition that did not mention the flu shot. 

The study was carried out during the fall of 2020, but the research group, which brings together behavioral science experts from institutions such as the University of Pennsylvania, Harvard University, Yale University, Columbia University and Carnegie Mellon University, started developing it before the onset of the coronavirus pandemic.

Co-author Dena M. Gromet, executive director of the Behavior Change for Good Initiative, told Fastinform that this texting project fits into the initiative's overarching mission of conducting large-scale field studies to find effective approaches for changing behavior in different domains, including health, education and finance. "We generally focus on identifying behavioral science strategies that are going to help people make positive changes in their lives," Gromet said.

The authors cited past research, prior to the spread of COVID-19, which suggests it is common for people to say that they intend to get a vaccine, but not follow through. Less than half of Americans were vaccinated during the 2019–2020 flu season, and tens of thousands of Americans are estimated to have died from the illness during that period, according to the Centers for Disease Control and Prevention. 

The COVID-19 vaccination effort in the U.S. has encountered many obstacles, including getting enough adults interested in the vaccine in order to potentially reach "herd immunity" against the virus. Vaccines are now available to all U.S. residents 16 years or older, but a Pew Research Center poll in December 2020 found that only 60% of Americans planned to get vaccinated. "Many Americans fail to get life-saving vaccines each year, and the availability of a vaccine for COVID-19 makes the challenge of encouraging vaccination more urgent than ever," the authors said in the paper.

Gromet and her colleagues first considered how people have previously responded to vaccine marketing. Prompting people to write down the exact date and time when they will get a flu shot at a workplace clinic, defaulting them into vaccination appointments, reminding high-risk individuals to get vaccinated and sending paper mail reminders have all been effective in the past and made vaccinations more likely, according to the paper.

The text messaging "nudges" tested in the study were all aimed at addressing the issue of people intending to get a vaccine but then failing to do so. The group of co-authors on the paper included 26 behavioral scientists, who worked in small teams to generate the 19 different text messaging protocols about the flu shot. 

Some of the 19 message conditions encouraging the flu shot involved interactive components, such as yes or no questions or links to external videos and surveys, and they also varied in timing and number of messages. Meanwhile, patients in the control condition only received standard text reminders about their appointments, including the date, time and location.

In the control condition without flu-specific reminders, 42% of patients received a flu vaccine on the day of their scheduled appointment or during the three days before it. The researchers considered this to be the baseline vaccination rate. Six out of the 19 intervention conditions resulted in a "statistically significant boost" in vaccinations, the authors said. And all 19 increased vaccination rates. Collectively, they increased them by an average of 2.1% over the baseline, for a relative increase of 5%.

All of the top-performing interventions used reservation-style messaging to remind patients that a flu shot was available and set aside for them at their next doctor's appointment. The most successful condition, which increased vaccinations by 11%, used two text messages, including one that read, "This is a reminder that a flu vaccine has been reserved for your appointment."

"The idea behind why it might have been so successful is related to the endowment effect and loss aversion — the idea that when you make a vaccine reserved for someone, it then feels like, 'That's mine, and if I don't go get it, I'm losing something or I'm giving something up that has been set aside for me,'" Gromet explained. The endowment effect is the notion that people more highly value something if they feel they own it in some sense; if they are told that they already "own" a flu shot, for example, it becomes more valuable to them.

Some of the least effective conditions included a joke about spreading the flu told by a dog to a cat and conveyed in picture form. The patients responded best to messages that were framed as reminders to get flu shots that were already reserved for the patient, and that had a similar style or tone that patients already expected to receive from their health care provider -- professional and straightforward, and not surprising, casual or interactive. The results did not differ significantly based on demographics or the health system to which the individual belonged.

"Overall, our findings show nudges sent via text messages to patients prior to a primary care visit and developed by behavioral scientists to encourage vaccine adoption can substantially boost vaccination rates at close to zero marginal cost," the authors reported.

The same impact should be true if a text message intervention system is used for other vaccines, such as COVID-19, Gromet said, as long as the individual is already open to getting a vaccine. These types of "nudges" are likely to be less successful with people who are strongly opposed to vaccines.

The Behavior Change for Good Initiative, which is an interdisciplinary team of more than 100 behavioral science experts affiliated with different universities, also conducted a corresponding study in partnership with Walmart. It tested 22 different types of flu shot intervention messages among roughly 700,000 pharmacy patients; the group is currently working to analyze that data, according to Gromet. A full paper has not yet been published, though Gromet said the early results are very similar to what was found in the Penn Medicine and Geisinger Health systems study.

"In the context that we studied it, these text message reminders were effective. And they're not that expensive to implement, it doesn't cost that much money to send a text message," Gromet said. "Our results indicate that simply reminding individuals that there's a vaccine waiting here for you [or] reserved for you can be an effective tool for helping increase vaccination rates."

The study, "A megastudy of text-based nudges encouraging patients to get vaccinated at an upcoming doctor's appointment," published April 29 in the Proceedings of the National Academy of Sciences, was authored by Katherine L. Milkman, Mitesh S. Patel, Linnea Gandhi, Heather N. Graci, Dena M. Gromet, Hung Ho, Joseph S. Kay, Timothy W. Lee, Alison Buttenheim, Jillian Hmurovic, Cait Lamberton, Ron Berman, Christophe Van den Bulte, Kevin G. Volpp and Angela L. Duckworth, University of Pennsylvania; Modupe Akinola and Maria Modanu, Columbia University; John Beshears, Leslie K. John, David Laibson, Jimin Nam and Todd Rogers, Harvard University; Jonathan E. Bogard, Hengchen Dai, Craig R. Fox, Jehan Sparks and Megan Weber, University of California Los Angeles; Christopher F. Chabris, Amir Goren, Michelle N. Meyer and Maheen Shermohammed, Geisinger Health System; Gretchen B. Chapman and Silvia Saccardo, Carnegie Mellon University; James J. Choi, Yale University; Matthew D. Hilchey, Melanie Kim, Renante Rondina and Dilip Soman, University of Toronto; Dean Karlan, Northwestern University; Brigitte C. Madrian, Brigham Young University; Caleb Warren, University of Arizona; Chalanda N. Evans and Christopher K. Snider, Penn Medicine; and Eli Tsukayama, University of Hawai`i-West O`ahu.

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