Targeting Behavioral Interventions Based on Past Behavior: Evidence from Vaccine Uptake

Behavior change interventions are widely used, but for whom are they most effective? We examine whether past behavior shapes the effectiveness of interventions designed to either (1) provide information to shift intentions or (2) help people follow through on existing intentions. We focus on encouraging flu vaccinations. In online experiments (Study 1; N=2,602), a video correcting misconceptions about flu vaccines increased vaccination intentions more effectively among people who had not been vaccinated in the prior flu season than those who had. In a field experiment with health systems (Study 2; N=14,760), the same information intervention increased vaccination intentions and uptake for people who had not been vaccinated in the prior season but it did not have a significant impact on those previously vaccinated, though the difference between these subgroups was not statistically significant. In contrast, in the same field experiment, a follow-through intervention designed to make vaccination salient and convenient increased vaccine uptake only among those previously vaccinated. In a large-scale field experiment where streamlined adaptations of these interventions were delivered by a pharmacy (Study 3; N=2,980,249), the follow-through intervention was again more effective for prior adopters than for previously unvaccinated individuals, while the information intervention had no impact for either subgroup. Collectively, these findings suggest that people’s past behavior may indicate whether insufficient intentions or follow-through challenges are the more relevant impediments to behavior change. Organizations can use this insight to decide whether and how to invest resources in behavior change interventions.