Overview
Public health campaigns continually seek effective ways to increase COVID-19 vaccination among adults. A 3-arm randomized controlled trial evaluated two theory-informed messaging approaches — attitudinal inoculation and CBT kernel messaging — against standard public health messaging to determine their impact on actual vaccine uptake and willingness. The study focused on adults in the United States who had received at least one prior COVID-19 dose but were not current with the latest vaccine season.
What Was Tested
The trial compared three brief, under-one-minute videos delivered online:
- Attitudinal inoculation: messages designed to strengthen resistance to misinformation about vaccine effectiveness using evidence-based refutations.
- CBT kernel messaging: content aimed at linking maladaptive thoughts to vaccination behavior, drawing from cognitive behavioral therapy principles to address barriers to getting vaccinated.
- Standard public health messaging: a typical PSA-style video without inoculation or CBT elements.
Participants were stratified by the presence of moderate-to-severe anxiety or depression symptoms and then randomized to one of the three arms. All participants received two follow-up reminders to get vaccinated and were instructed to view the content online.
Key Outcomes
The primary outcome was receipt of a COVID-19 vaccine dose within four weeks post-intervention. Secondary outcomes included willingness to receive another dose and immediate post-intervention intentions to make a vaccination plan.
Results showed low vaccine uptake across all groups (1.21% overall) with no statistically significant differences between the inoculation, CBT kernel, and standard messaging arms. Vaccination willingness at four weeks also did not differ meaningfully across arms. Subgroup analyses indicated a potential signal: among participants who were worried about COVID-19, inoculation messaging slightly increased willingness to vaccinate in some analyses, though uptake remained low.
Subgroup Insights
Analyses explored whether mental health status moderated effects. Across participants with or without anxiety/depression symptoms, there were no consistent differences in vaccine uptake or willingness between intervention arms. Some post-hoc findings hinted that those with elevated worry could respond more to inoculation messaging, suggesting a potential target for refined strategies in future work.
Interpretation and Implications
The trial contributes to the evidence base on theory-informed vaccine messaging but emphasizes the challenge of translating messaging strategies into tangible behavior change. Several factors likely shaped the null findings:
- Context: The study occurred during a period of relatively low respiratory illness activity and after vaccines were widely available, potentially dampening urgency and uptake.
- Interventions: Short videos, while scalable, may not provide enough depth to shift entrenched beliefs or motivate action without additional engagement or support.
- Follow-up windows: A four-week horizon may be insufficient to observe meaningful uptake in this population.
Future Directions
Researchers should explore longer or multi-component interventions, incorporate motivational interviewing techniques, and assess effects during periods of higher transmission. Additional work could illuminate whether inoculation strategies are more effective for specific subgroups or when combined with personalized outreach and easier access to vaccination sites.
Public Health Takeaway
While theory-informed messaging holds conceptual promise, this study underscores the difficulty of moving from improved attitudes or willingness to actual vaccination in a real-world setting. Enhanced strategies that blend brief messaging with ongoing engagement and accessible vaccination opportunities may be necessary to lift uptake, especially among individuals facing mental health challenges.
Ethics and Transparency
The study followed CONSORT guidelines for psychosocial interventions, with web-based consent and compensation provided to participants. Limitations include potential underpowering for small but meaningful effects and the post-pandemic context limiting generalizability to higher-risk periods.
