COVID-19 Booster Vaccine Messaging in Emergency Departments: A Cluster Randomized Clinical Trial

Patient uptake of updated COVID-19 vaccines is crucial for reducing severe outcomes, yet national uptake remains low.

To determine if tailored messaging or simple inquiry about vaccine acceptance increases 30-day uptake of updated COVID-19 vaccines among emergency department (ED) patients.

This 3-arm, cluster randomized clinical trial conducted from January 29 to June 18, 2024, enrolled adult ED patients who had not received a COVID-19 vaccine in the prior 6 months across 6 EDs in San Francisco, California; Philadelphia, Pennsylvania; Houston, Texas; and Durham, North Carolina.

Intervention M involved tailored messaging about updated COVID-19 vaccines and inquiry about vaccine acceptance. Intervention Q involved only inquiry about vaccine acceptance. Usual care (no messaging or vaccine acceptance questions) served as the control.

The primary outcome was updated COVID-19 vaccine receipt within 30 days of the ED visit, assessed via electronic health record review and follow-up telephone calls. Secondary outcomes included vaccine acceptance and vaccination during the ED visit. Outcomes were also compared between study sites that had the updated COVID-19 vaccine available and those that did not.

Of 852 participants (median age, 47 years [IQR, 33-63 years]; 464 [54.5%] women), 247 (29.0%) were in the intervention M group, 273 (32.0%) in the intervention Q group, and 332 (39.0%) in the control group. Vaccine uptake at 30 days was not significantly higher in either the intervention M group compared with control (14 participants [5.7%] vs 10 [3.0%]; absolute difference, 2.7 percentage points [pp] [95% CI, -0.8 to 6.3 pp]) or the intervention Q group compared with control (11 [4.0%] vs 10 [3.0%]; absolute difference, 1.0 pp [95% CI, -2.0 to 4.2 pp]). However, at sites where vaccines were available, the intervention M group had higher uptake compared with control (13 of 132 [9.8%] vs 5 of 150 [3.3%]; absolute difference, 6.5 pp [95% CI, 0.5-12.5 pp]).

In this cluster randomized clinical trial of adult ED patients, tailored messaging and simple inquiry alone did not significantly increase 30-day updated COVID-19 vaccine uptake among patients. The slight increase in uptake among participants in the EDs that had access to the updated COVID-19 vaccines suggested that vaccine availability was an effect modifier, underscoring the importance of opportunity and convenience in vaccine delivery.

ClinicalTrials.gov Identifier: NCT06156215.