Beyond One-Size-Fits-All Nudges

Messages tailored to past vaccination behavior can meaningfully boost uptake for some

Behavioral nudges have long followed a one-size-fits-all playbook. Research has consistently looked for the most impactful way to encourage a given behavior — save more, exercise more, get vaccinated — with a focus on what might work for everyone.

Research published in Organizational Behavior and Human Decision Processes suggests that personalizing nudges based on past behavior may be an even more effective approach. The researchers also find evidence that the richness of a given nudge — a two-minute video rather than a brief text — can matter.

UCLA Anderson’s Ilana Brody, a Ph.D. student, and Hengchen Dai, Carnegie Mellon’s Silvia Saccardo, University of Pennsylvania’s Katherine Milkman, Angela Duckworth and Dena Gromet, and Ascension’s Mitesh Patel use flu vaccination as their testing ground to address the fact that behavioral roadblocks exist along a spectrum.

Some of us haven’t yet bought into the value of a given behavior. In academese, such people haven’t yet formed the intention. Other people are already on board with the value of a given behavior but struggle with follow-through; they are textbook examples of the intention–action gap. They don’t need a nudge explaining why a behavior is in their best interest; they need help converting intention into action.

In a field experiment involving nearly 3 million people designed to encourage flu vaccination, the researchers found that nudging people who had been vaccinated the prior year with a reminder to schedule a shot increased vaccination rates by about 1 percentage point compared with past vaccinators who did not receive a flu-related message. 

While a 1-percentage-point bump seems modest, it translates into meaningful benefit at scale, given that vaccinations are one of the most cost-effective places where nudging can help. Based on data from the partnering pharmacy chain, the researchers estimate that every $100 spent on the follow-through nudge for past adopters yielded approximately 55 additional flu inoculations.

But the same large field test found that participants who hadn’t been vaccinated the prior year were not swayed more by an informative message compared with a simple reminder. That result ran counter to what the researchers had found in preliminary experiments.

A Formatting Issue?

An initial lab experiment involving about 2,600 participants served as a pretest of past behavior as a valuable factor in nudging. Some participants watched a two-minute video explaining the value of flu vaccinations, and others saw a video featuring people who had gotten the flu sharing their experience. Both approaches were designed to test an information-rich nudge. A control group viewed a video focused on chronic illness and the value of exercise, absent any mention of the flu or flu vaccine.

Among participants who hadn’t gotten a flu shot the prior year, self-reported intention to get vaccinated after viewing one of the informative videos was nearly 13 percentage points higher than among nonvaccinators in the control group. For people who had already been vaccinated the prior year, the videos made virtually no difference. This aligns with the idea that information is useful for people who have yet to form an intention, but of little help for people who already intend to act and instead struggle with follow-through.

A second preliminary study deepened that insight. More than 14,000 patients from two health care systems who had routine primary care appointments scheduled — and who hadn’t yet received a flu vaccine for the current season — received a text message. ​Some patients received a standard text message reminding them of their upcoming appointment, while others received additional messages encouraging them to get a flu shot during their visit. ​These messages also included a link to either an informational video about the flu vaccine or a control video about exercise. The message came from the patient’s own doctor, potentially giving it more resonance. 

For individuals who watched the video but hadn’t received a flu shot in the prior year, the informational video correcting misconceptions about the flu vaccine increased uptake by 3.8 percentage points. ​In contrast, simple reminder texts to get vaccinated had no impact on this group. ​For those who had been vaccinated in the prior year, the simple reminder text increased uptake by 3.8 percentage points, while the informational video did not significantly affect their behavior.

Context Seems to Matter

When this pattern was tested in the large field test of pharmacy clients, the results shifted. The follow-through intervention still worked for prior adopters, though the effect shrank to roughly a 1-percentage-point boost. For nonvaccinators, however, the informational nudge did not help.

One key difference was format. The pharmacy that worked with the researchers insisted that the informational content had to be compressed into a brief text message rather than delivered through a two-minute video. The researchers note that changing the minds of people who hadn’t been vaccinated the prior year may require sustained attention that a richer format can better provide.

They also suggest that the smaller effect on past vaccinators who were given the reminder text may reflect a difference in friction. In the earlier health-system experiment, participants already had a scheduled doctor’s appointment and an implicit endorsement from the doctor whose name was attached to the text. The text from the pharmacy still required them to schedule and keep an appointment. 

While those potential explanations require further research, this study suggests practical ways more bespoke nudging deserves consideration. For example, an employee who completed last year’s compliance training may respond best to a reminder to sign up again, while an employee who skipped last year’s training may benefit more from a nudge explaining why the training matters. The same logic applies to wellness programs or preventive health screenings. Meeting people where they are on the intention-action spectrum can lead to more resonant nudges that help, at least at the margin, improve outcomes.