CARD (Comfort Ask Relax Distract) for school-based immunizations in Calgary, Canada: a pragmatic cluster trial

School-based immunizations are fear-inducing events for many students and contribute to vaccine hesitancy. We developed an immunization delivery framework called the CARD (Comfort Ask Relax Distract) system that incorporates evidence-based interventions to improve the experience (eg, reduce fear, pain, dizziness). We evaluated CARD in grades 6 and 9 students in Calgary, Canada. In this pragmatic, hybrid, effectiveness-implementation, cluster trial, we randomized 8 Community Health Centres providing regional immunization services to CARD or control (usual care). In the CARD group, public health staff educated students about CARD and planned processes to reduce fear cues and support student coping choices during immunization. Students self-reported fear, pain, and dizziness during immunization using a 0-10 numerical rating scale; staff recorded procedure details, including vaccines administered, fainting episodes, and coping strategies used. Staff participated in focus groups afterward. Altogether, 8839 children from 105 schools in the 2019 to 2020 school calendar year were included. Fear was lower for CARD (mean = 3.6 [SD = 3.1] vs control 4.1 [3.2]; mean difference = -0.5; 95% confidence interval = -0.74 to -0.21; P < 0.001). Effectiveness persisted after stratification by student gender (male and female) and grade level (grade 6 and grade 9). Other symptoms did not differ. Compared with control, CARD students used peers, privacy, muscle tension, and topical anesthetics more; verbal distraction, deep breathing, and adult support were used less frequently ( P < 0.05, all analyses). Immunization rate did not differ. Staff reported positive to neutral attitudes about CARD. In summary, this pragmatic trial demonstrated that CARD improved the immunization experiences of students at school.