Background: Despite the availability of effective vaccines, flu and COVID-19 uptake remains suboptimal, particularly among Indigenous communities who face unique barriers to accessing public health information. While previous research has evaluated health communication message content and design, fewer studies have systematically compared different dissemination strategies for the same intervention, leaving gaps in understanding optimal approaches for reaching marginalized populations.

Objective: We conducted a three-arm dissemination study designed to compare the effectiveness of different strategies for distributing COVID-19 and flu vaccine promotion videos targeting Indigenous Peoples residing in California, including American Indian, Alaska Native, Native American, and migrant Indigenous communities from Latin America.

Methods: Following extensive formative work including cross-sectional surveys, social network analyses, discrete choice experiments, and focus groups conducted with guidance from an Indigenous Community Advisory Board, we developed two 30-second vaccine promotion videos available in English, Spanish, and four Indigenous languages (Purépecha, Mam, Zapoteco, and Mixteco). We tested three dissemination strategies over one month: (1) paid social media advertisements on Facebook and Instagram targeting high Indigenous population areas, (2) distribution through community-based organizations using their established communication channels, and (3) peer-to-peer sharing through Indigenous community members (“seeds”) recruited from previous research. Follow-up surveys to measure reach, engagement, and message impact across dissemination strategies were conducted.

Results: We collected data from 507 people, including 208 from the “seeds” arm, 265 from social media and 34 from CBOs. Preliminary analysis suggests that intervention arm was not associated with the likelihood of someone planning to get the COVID or flu vaccine in the future. However, trust in the person sending them the message was strongly and significantly associated with likelihood of future vaccination.

Conclusions: This study addresses a critical gap in health communication research by providing a systematic methodology for comparing digital dissemination strategies within Indigenous communities. Our findings suggest that trust in the messenger might be the most important factor in behavior change.