Information Provision and Consistency Framing to Increase COVID-19 Booster Uptake

The proposed randomized controlled trial will take place a few weeks after UCLA Health notified its patients about bivalent COVID-19 boosters. The trial will test whether text-based reminders can increase uptake of bivalent COVID-19 boosters and examine different ways to elevate intentions to get the booster. This trial will include a randomly selected ~40% of patients from all UCLA Health patients eligible to receive the COVID-19 bivalent booster at the time of the study, with 35% of the remaining eligible patients randomly allocated to another trial (Pre-registration title: "Boost intentions and Facilitate Action to Promote Covid-19 Booster Take-up") and 25% randomly allocated to a third trial (Pre-registration title: "Effects of Prompt to Bundle Covid-19 Booster and Flu Shot"). The three trials will be run simultaneously.

Patients randomly selected for this trial will be randomized at an equal share to 7 conditions: an Holdout condition that does not receive a text reminder and 6 additional conditions that receive a text message (simple reminder, uniqueness information reminder, eligibility information reminder, severity information reminder, consistency reminder, and consistency and uniqueness information reminder; see description in the Arm/Interventions section). Within each arm, patients are further randomized into one of the 33 time slots for when they will receive the text message (i.e., 3 time points per day including 9am, 12pm, 4pm for 11 days). Days 1-4 and 8-11 have slightly fewer patients than Days 5-7.

First, to test whether the text reminders increase vaccine uptake, the investigators will compare the holdout condition to the combination of the 6 reminder arms.

The investigators will also investigate additional questions:

1. The investigators will investigate how the information provision strategies affect vaccine uptake. For this purpose, the investigators will compare vaccine uptake and link click rates between (1) the uniqueness information reminder, (2) the eligibility information reminder, and (3) the severity information reminder. If there are significant differences across three information provision reminders in a given outcome, the investigators will separately compare these three reminders with the simple reminder and the holdout arm. If there are not significant differences across the three information provision reminders in a given outcome, the investigators will compare the average of these three reminders with the simple reminder and holdout. The investigators will also compare the simple reminder with the holdout arm. For the severity information reminder, the investigators have competing predictions. On one hand, highlighting underestimated severity may increase the perceived importance of the vaccine; on the other hand, the negative valence of this message may create reactance, leading people to avoid thinking about COVID-19 and vaccination.
2. The investigators will investigate how the consistency framing affects vaccine uptake and whether the combination of consistency and uniqueness information has a positive effect. On one hand, the psychological literature about the consistency principle suggests that people strive to behave consistently with their past actions and positions; thus, reminding people that they have completed the primary series and have done a good job at protecting their health may motivate them to consistently take care of themselves by getting the bivalent booster. On the other hand, patients may get complacent after being reminded that they have already finished the primary series, thinking that they have already completed the necessary steps to protect themselves. Hence, the investigators have competing predictions about whether the consistency framing can effectively increase vaccine uptake. The combination of consistency and uniqueness information about how the bivalent booster differs from the previous doses may be most powerful. To understand the role of consistency framing, the investigators will compare the consistency reminder with the simple reminder (in both vaccine uptake and link click rates) and the holdout condition (in vaccine uptake only). To test the effect of consistency framing and uniqueness information, the investigators will compare the consistency and uniqueness information reminder with the consistency reminder, the uniqueness information reminder, simple reminder, and holdout, respectively.
3. The investigators will explore the role of the time when a text message is sent. The investigators will examine how the effect of text reminders (i.e., the combination of the 6 reminder arms vs. holdout) varies across days and times. As additional specifications, the investigators will control for the time trend and analyze all patients who have not gotten the bivalent booster in California or scheduled a booster appointment at UCLA Health the day before the trial starts.