Enhancing vaccine uptake is a critical public health challenge¹. Overcoming vaccine hesitancy^2,3 and failure to follow through on vaccination intentions³ requires effective communication strategies^3,4. Here we present two sequential randomized controlled trials to test the effect of behavioural interventions on the uptake of COVID-19 vaccines. We designed text-based reminders that make vaccination salient and easy, and delivered them to participants drawn from a healthcare system one day (first randomized controlled trial) (n = 93,354 participants; clinicaltrials number NCT04800965) and eight days (second randomized controlled trial) (n = 67,092 individuals; clinicaltrials number NCT04801524) after they received a notification of vaccine eligibility. The first reminder boosted appointment and vaccination rates within the healthcare system by 6.07 (84%) and 3.57 (26%) percentage points, respectively; the second reminder increased those outcomes by 1.65 and 1.06 percentage points, respectively. The first reminder had a greater effect when it was designed to make participants feel ownership of the vaccine dose. However, we found no evidence that combining the first reminder with a video-based information intervention designed to address vaccine hesitancy heightened its effect. We performed online studies (n = 3,181 participants) to examine vaccination intentions, which revealed patterns that diverged from those of the first randomized controlled trial; this underscores the importance of pilot-testing interventions in the field. Our findings inform the design of behavioural nudges for promoting health decisions⁵, and highlight the value of making vaccination easy and inducing feelings of ownership over vaccines.

提高疫苗接种率是一项重大的公共卫生挑战¹。克服疫苗犹豫^2,3和未能贯彻疫苗接种意图³需要有效的沟通策略^3,4。在这里，我们提出了两项​​连续的随机对照试验，以测试行为干预对 COVID-19 疫苗摄取的影响。我们设计了基于文本的提醒，使疫苗接种变得突出和容易，并在一天（第一次随机对照试验）（ n  = 93,354 名参与者；临床试验编号 NCT04800965）和八天（第二次随机对照试验）将它们发送给来自医疗保健系统的参与者( n = 67,092 人；临床试验编号 NCT04801524）在收到疫苗合格通知后。第一个提醒将医疗保健系统内的预约率和疫苗接种率分别提高了 6.07 (84%) 和 3.57 (26%) 个百分点；第二次提醒将这些结果分别提高了 1.65 和 1.06 个百分点。当第一个提醒旨在让参与者感受到疫苗剂量的所有权时，它的效果更大。然而，我们没有发现任何证据表明将第一个提醒与旨在解决疫苗犹豫问题的基于视频的信息干预相结合会提高其效果。我们进行了在线研究（n = 3,181 名参与者）检查疫苗接种意图，这揭示了与第一次随机对照试验不同的模式；这突出了实地试验性干预措施的重要性。我们的研究结果为促进健康决策的行为助推器设计提供了信息⁵，并强调了使疫苗接种变得容易和引起对疫苗的所有权感的价值。