Behavioural nudges increase COVID-19 vaccinations

Increasing COVID-19 vaccination rates is a critical public health challenge. Vaccine hesitancy and failure to act on vaccination intentions hinder progress. Effective communication strategies are needed to overcome these barriers. This study focuses on the use of behavioral nudges—subtle interventions that influence behavior without restricting choices or significantly altering economic incentives—to improve vaccine uptake. Previous research has shown the effectiveness of nudges in various health-related decisions. This study uses two large-scale RCTs to test the effectiveness of text-message reminders, designed to address barriers such as forgetfulness and inconvenience, in boosting COVID-19 vaccination rates. The study also explores whether combining these reminders with additional interventions, such as behaviorally informed messaging and video-based information, further enhances uptake. The high rate of vaccine hesitancy, even with readily available vaccines, emphasizes the need for such research to inform effective public health strategies. The context is the COVID-19 pandemic, which has imposed significant costs globally and where high levels of vaccine hesitancy remain a serious obstacle to controlling the pandemic.

The paper reviews existing literature on vaccine uptake, highlighting the challenges posed by vaccine hesitancy and the need for effective communication strategies. It cites studies that explore interventions aimed at boosting vaccination intentions and those focusing on helping people follow through on their intentions. The concept of 'nudges' as low-cost behavioral interventions is introduced, with examples of their successful application in other health-related domains, such as healthy eating and influenza vaccinations. The effectiveness of reminders as a popular nudge is discussed, alongside research indicating their effectiveness in various policy domains. The review sets the stage for the study by demonstrating the need for and the potential of behavioral interventions in improving vaccine uptake.

The study employed two sequential, large-scale randomized controlled trials (RCTs) conducted within the UCLA Health system. Participants were eligible patients who received an initial invitation for a COVID-19 vaccine. The first RCT enrolled participants on the first weekday after receiving the initial invitation, randomizing them to receive a text-message reminder or not. A 2x2 factorial design within the reminder arm tested the effect of adding either behaviorally informed messaging (inducing feelings of ownership) or a video-based information intervention. The second RCT enrolled participants who had not scheduled an appointment after the first reminder, again randomizing them to receive a second reminder or not. Both RCTs had a 1:1 randomization ratio. The primary outcome was appointment scheduling within six days of the reminder, and the secondary outcome was vaccination within four weeks. The study also incorporated online experiments using Amazon's Mechanical Turk and Prolific Academic, exploring the impact of the interventions on vaccination intentions, comparing these results with those from the field trials. All exclusion criteria and analyses were pre-registered.

The first reminder in the first RCT increased appointment and vaccination rates within the UCLA Health system by 6.07 and 3.57 percentage points, respectively. The reminder was more effective when designed to induce feelings of ownership over the vaccine dose. The second reminder produced smaller but still significant increases in appointment and vaccination rates (1.65 and 1.06 percentage points, respectively). The combination of the first reminder and the video-based intervention showed no additional benefit in increasing uptake. Analyses showed that the effect of reminders persisted over several weeks, suggesting a sustained impact on vaccination rates. The effects of reminders were consistent across various demographic subgroups, including racial and ethnic minorities and participants under 65 years old. However, online experiments exploring vaccination intentions showed a discrepancy with the field trial results, suggesting the importance of pilot testing interventions. The study also found that the major barrier was not vaccine hesitancy, but rather the failure to schedule an appointment after receiving eligibility information.

The findings demonstrate the effectiveness of simple, well-designed behavioral nudges, specifically text-message reminders, in significantly increasing COVID-19 vaccination rates. The strategy of inducing feelings of ownership proves particularly impactful. The lack of additional benefit from combining reminders with a video-based information intervention suggests a need for further investigation into the role of information-based strategies in overcoming vaccine hesitancy. The discrepancies between the field trial and online experiment results underscore the importance of real-world testing for behavioral interventions. The study's findings have significant implications for public health policy, suggesting that these low-cost interventions can be effectively implemented to improve vaccination rates, particularly by targeting the scheduling barrier.

This study demonstrates the significant impact of simple behavioral nudges, specifically text-message reminders and the framing of vaccine ownership, in increasing COVID-19 vaccination rates. The results emphasize the need for evidence-based policy making and highlight the potential of low-cost interventions to significantly improve public health outcomes. Future research could focus on refining these interventions, testing their effectiveness in diverse settings and populations, and exploring the optimal timing and frequency of reminders.

The study's limitations include the sample being drawn primarily from a single healthcare system (UCLA Health), potentially limiting the generalizability of the findings to other settings. The reliance on self-reported data for some outcomes also presents limitations. The discrepancy between field and online experimental findings highlight the complexities of translating laboratory results into real-world settings.