Beyond Automatic Reminders: Adaptive Layered Communication Strategies to Sustain Young Adult Engagement in a Longitudinal Intervention Study

Digital health interventions offer promising opportunities for behavioral change among young adults, but maintaining longitudinal trial engagement is difficult. This study examined the adaptive layered communication strategies (ALCS) developed collectively through aniterative loop with community members in the Student Health Initiative for Eliminating HPV Diseases (SHIELD) study. These strategies included welcome videos, personalized messages (e.g., thank-you texts, birthday messages, exam period check-ins), and memes. Compared to the period/phase before ALCS, participants exposed to ALCS demonstrated significantly higher survey completion rates at 6 months (76.09% vs. 60.51%, p = .01) and 9 months (78.08% vs. 65.64%, p = .05). Moderation analyses revealed a phase×school type interaction (p = .04): completion rose from 50.05% to 75.95% among public school students (p = .03), while private school rates remained stable ( > 75.00%), suggesting a ceiling effect (p = .41). While automated reminders remain valuable, researchers developing longitudinal digital health interventions should consider a "cocktail" approach, which combines reliable automation with authentic, timely, and culturally tuned human touches, to sustain engagement, particularly in lower-engagement contexts (e.g. public schools).