Behavioural Nudges Increase COVID-19 Vaccinations

"...research has implications for enhancing the uptake of life-saving vaccines in general, as it highlights the power of making vaccination easy and eliciting feelings of ownership over the vaccine."

Overcoming vaccine hesitancy and the failure to follow through on vaccination intentions requires effective communication strategies to maximise vaccine uptake. This paper describes two sequential randomised controlled trials (RCTs) conducted to examine whether nudges - low-cost behavioural interventions such as reminders that are carefully designed to reduce barriers to following through - could improve the uptake of COVID-19 vaccines. The study further examines the benefits of combining reminders with additional interventions, including (i) behaviourally informed messaging designed to amplify individuals' desire to get vaccinated and (ii) a traditional information-provision intervention aimed at correcting the misconceptions that drive vaccine hesitancy.

The researchers designed text-based reminders that are meant to make vaccination salient and easy, and they delivered them to participants drawn from a United States (US) healthcare system one day (first RCT, with n = 93,354 participants) and eight days (second RCT, with n = 67,092 participants) after they received a notification of vaccine eligibility, starting from January 29 2021. In both RCTs, the researchers randomised whether participants received text-message-based reminders or not. All reminders shared two elements that were intended to address two barriers to action: (i) they made vaccination top of mind to curb forgetfulness and prompt people to adopt the target behaviour; and (ii) they sought to reduce inconvenience by including a link to the appointment-scheduling website and allowing participants to easily book their appointment immediately.

On the first reminder date, the researchers randomly assigned participants enrolled in the first RCT at a 4:1 ratio to the "follow-through reminder" arm, in which they received a text reminder at 15:00 hours that encouraged them to schedule a vaccination appointment, or to the "holdout" arm, in which they did not get a reminder. The researchers nested a 2 × 2 factorial design within the "follow-through reminder" arm to test whether reminders become more effective when combined with another behaviourally informed intervention to motivate action and/or with an information intervention that aims at shifting vaccination intentions:

1. The first factor varied whether the reminder attempted to further amplify people's desire to act by inducing feelings of psychological ownership over the vaccine. Reminders containing the ownership intervention indicated the vaccine had "just been made available for you" and encouraged participants to "claim your dose".
2. The second factor manipulated whether the reminder contained a link to a 2-minute video (in English or Spanish) that provided information on COVID-19 and vaccine effectiveness, with the goal of correcting common misconceptions and boosting vaccination intentions.

All reminder types outperformed the holdout arm in this first RCT. The reminder boosted appointment and vaccination rates within the healthcare system by 6.07 (84%) and 3.57 (26%) percentage points, respectively. The top-performing reminder type contained the ownership language, and it boosted appointment and vaccination rates by 6.83 (94.84%) and 4.12 (29.63%) percentage points, respectively, relative to the holdout arm. However, there was no evidence that combining the first reminder with the video-based information intervention designed to address vaccine hesitancy heightened its effect.

The average effects of follow-through reminders on both appointments and vaccinations were comparable across white (n = 49,909), Hispanic (n = 10,624), Black (n = 5,109), and Asian (n = 7,553) participants. "Identifying solutions to improving vaccine uptake among racial and ethnic minority groups is critical, as these groups have been disproportionately hurt by the COVID-19 pandemic...and tend to experience increased vaccine hesitancy..."

Participants who did not schedule their vaccine appointment a few days after the first reminder may have forgotten about it, been procrastinating, or been more hesitant than those who got vaccinated. The second RCT studied the effect of sending these participants a second text reminder. On the second reminder date, the researchers randomised eligible participants at a 6:1 ratio to receive another text message at 15:00 hours that reminded them of vaccine availability and provided easy access to the scheduling website (the follow-through reminder arm) or to not receive the text message (the holdout arm). To harness other psychological principles to motivate people to act, the researchers randomised participants within the follow-through reminder arm to receive one of six messages that leveraged additional behavioural insights.

Getting a second reminder increased participants' likelihood of scheduling the first-dose appointment within six days by 1.65 percentage points (53.36%) and obtaining the first dose within four weeks by 1.06 percentage points (17.23%), relative to the 3.10% appointment rates and 6.16% vaccination rates in the holdout arm.

The researchers also performed online studies (n = 3,181 participants) to examine vaccination intentions, which revealed patterns that diverged from those of the first RCT; this experiment underscores the importance of pilot-testing interventions in the field.

In conclusion, this research "highlights that behavioural science insights can increase and speed up COVID-19 vaccinations at close-to-zero marginal cost. Text-based reminders designed to overcome barriers to scheduling can effectively encourage vaccinations across different demographic groups, with effects persisting for at least eight weeks. These effects are heightened when follow-through reminders leverage psychological ownership, making people feel that a dose of the vaccine belongs to them. However,...more work is needed to uncover when information interventions can help to overcome vaccine hesitancy."