Development and Preliminary Evaluation of the OCODES Digital Strategy in Response to Health Misinformation: Nominal Group Technique and Retrospective Usability Evaluation Study

Background: Health misinformation has intensified worldwide, especially in digital environments, where low health and media literacy increase vulnerability. Thus, the MEDIATICH program of the University of Zaragoza launched OCODES (Observatorio Contra la Desinformación en Salud), a participatory digital initiative designed to promote health media literacy and provide evidence-based information through a web platform and social media channels. Objective: This study describes the co-design and development of the OCODES strategy using 2 sequential nominal group technique (NGT) sessions, and assesses its preliminary usability, preliminary user perception, and user engagement after 6 months of activity as a digital initiative developed in response to health misinformation. Methods: NGT1 (n=15) aimed to identify and prioritize interventions to strengthen health literacy through an individual yes or no prioritization process, while NGT2 (n=18) translated selected priorities into concrete digital products, including website structure, social media selection, content lines, and interaction mechanisms. In addition, routine user feedback and website analytics data generated through the OCODES digital channels during the first 6 months of activity were retrospectively examined. Usability was explored using the System Usability Scale (SUS), while preliminary user perception was described through 2 study-specific indicators available in the public feedback tools: perceived usefulness (1-5 Likert scale) and willingness to recommend the website. Google Analytics provided complementary website engagement metrics. Results: NGT-1 generated 11 interventions grouped into four categories. Digital actions were prioritized as the core strategy: a health dissemination portal and social media interventions in the context of health misinformation each achieved 93.3% (14 of the 15 participants) agreement. NGT-2 defined the digital architecture of OCODES, including a central website and presence on LinkedIn (Meta), X (formerly known as Twitter; X Corp), and Instagram (Meta), and established guiding principles such as transparency, scientific rigor, accessibility, and clear communication. A total of 99 adults provided routine usability feedback (65/99, 65.7% women; mean age 44.7, SD 12.54 y). The mean SUS score was 83.10 (SD 10.09), with 94.9% (94/99) achieving adequate usability (SUS ≥68). Perceived usefulness scored 4.52 (SD 0.71), and 97.9% (97/99) of users who provided feedback indicated that they would recommend the site. Web metrics showed 5769 new users, 1935 returning users, 19,003 page views, a bounce rate of 53.32%, a total of 3.28 pages per active user, and 4.95 events per session, indicating strong initial engagement. Conclusions: OCODES is a feasible and well-received digital strategy developed through a participatory, consensus-driven process. Its favorable usability indicators, positive preliminary user perception, and encouraging early engagement metrics support its feasibility. However, the current findings do not provide evidence of effectiveness in reducing health misinformation or improving health media literacy. Future efforts should focus on reaching vulnerable populations, expanding evaluation approaches, and assessing long-term impact.