Overview
Public health messaging remains a critical lever for increasing COVID-19 vaccination among adults. A recent randomized controlled trial evaluated two theory-informed messaging approaches—attitudinal inoculation and cognitive behavioral therapy (CBT) kernels—against standard public health messaging to determine if these brief, scalable interventions could raise vaccine uptake and willingness in a US adult population with prior vaccination history.
Study Design and Population
The study was a 3-arm, parallel-group, assessor-blinded trial conducted in the United States. Adults aged 18+ who had received at least one prior COVID-19 vaccine but none since September 2023 were randomized to receive one of three brief videos (<1 minute): (1) attitudinal inoculation, (2) CBT kernel messaging, or (3) standard public health messaging. Enrollment occurred April 2024 with follow-up at 4 weeks. Participants were stratified by the presence of moderate to severe anxiety or depression symptoms, assessed via validated scales.
Participants were drawn from the CHASING COVID Cohort Study, a diverse national sample. The trial aimed to test whether these messaging strategies could translate into actual vaccine uptake or, at minimum, increased willingness to vaccinate among adults already contemplating vaccination.
Interventions
All videos were designed to be concise, engaging, and devoid of logos or explicit branding. The inoculation video targeted misinformation about vaccine effectiveness, using pre-emptive refutations and logical argumentation. The CBT kernel video linked maladaptive thought patterns to vaccination behavior, modeling how reframing beliefs could facilitate preventive action. The standard arm used a brief, conventional public health message without inoculation or CBT elements. Following the videos, participants received two reminders via SMS or email with a link to a vaccine venue locator.
Outcomes and Analysis
The primary outcome was receipt of a COVID-19 vaccine dose within 4 weeks of the intervention. Secondary outcomes included vaccination willingness at 4 weeks and pre-/post-trial willingness and appointment plans. Analyses followed an intention-to-treat framework, using robust Poisson models to estimate risk ratios and risk differences, with multiple imputation to address missing data and dropout.
Key Findings
Across 1,403 analyzed participants, overall vaccine uptake at 4 weeks was low (1.21%), with no statistically significant differences among arms: CBT kernel (about 1.5%), inoculation (about 0.9%), and standard messaging (about 1.3%). Willingness to vaccinate at 4 weeks also did not differ meaningfully by arm. These null results held for participants with and without anxiety or depression symptoms, suggesting that the short, stand-alone messages did not meaningfully shift vaccination behavior in this context.
Subgroup Observations
Post hoc analyses hinted that inoculation messaging might slightly increase vaccination willingness among those worried about COVID-19, though this did not translate into higher uptake at 4 weeks. Other stratifications, including age and pretrial beliefs about vaccine efficacy, showed no robust differences in primary or secondary outcomes. Sensitivity analyses largely corroborated the primary results, underscoring the stability of the null findings across analytic approaches.
Implications for Public Health Messaging
The trial highlights the difficulty of moving from vaccine willingness to actual uptake using brief digital videos, even when grounded in behavioral theory. While inoculation theory and CBT kernels have shown promise in other domains, their standalone application as public health messages may be insufficient to drive meaningful behavior change among adults with prior vaccination and varying mental health symptoms. The findings emphasize the need for more targeted, potentially multi-session or tailored interventions, and for evaluating messaging during periods of higher transmission or vaccine demand.
Limitations and Future Directions
Contextual factors—such as timing outside peak respiratory virus season and overall low transmission—likely constrained uptake. The study also faced power limitations to detect small but meaningful effects and relied on short video content. Future work could explore longer or mixed-media messaging, incorporate motivational interviewing components, and assess longer-term outcomes during higher-risk periods to determine if theory-informed approaches can exert a stronger influence on vaccination behavior.
Conclusion
In a real-world US setting, theory-based messaging—attitudinal inoculation and CBT kernels—did not outperform standard messaging in increasing COVID-19 vaccination uptake over four weeks among adults with prior vaccination history. The results contribute to the evidence base on how best to translate behavioral theories into scalable, effective public health communications, while pointing to the necessity of more nuanced, persistent strategies to overcome vaccine hesitancy and achieve lasting protection.
