Digital Campaign to Promote COVID-19 Vaccination and Clinical Trial Participation Among Vietnamese Americans: Observational Engagement Study

Background The COVID-19 pandemic necessitated innovative approaches to health communication, particularly for non–English-speaking communities. Vietnamese Americans, who report lower rates of English proficiency, faced unique challenges accessing facts and subsequent “infodemic” of rapidly spreading information. Objective This study aims to evaluate the feasibility and engagement patterns of a community-engaged bilingual digital campaign delivered through Google’s Display & Video 360 (DV360) platform to Vietnamese Americans in Texas, comparing performance across multiple advertising formats. Methods We implemented a 2-phase digital campaign on (DV360): static display advertisements (Phase 1: February 15-March 31, 2022) and audiovisual content (Phase 2: May 26-June 30, 2022). With community-based organizations (CBOs), 6 static displays, 2 videos, and 2 audio advertisements were developed in English and Vietnamese using focus group review and back-translation. Advertisement placements were constrained to a Texas Vietnamese audience segment. Total budget was US $9,472.54. Performance was evaluated using impressions, click-through rate (CTR), cost metrics, cost per click (CPC), cost per thousand impressions (CPM), and cost per view (CPV), with Wilson 95% CI, and two-proportion z-tests for substantive comparisons. Results The campaign generated 4,974,357 impressions, reaching approximately 1.4 million unique users in Phase 1, and 105,000 in Phase 2. Vietnamese-language display advertisements achieved a higher CTR than English-language advertisements (0.105% vs 0.046%; χ 1 ²=480.6; P <.001; risk ratio 2.29). Mobile placements outperformed desktop within each language (Vietnamese mobile 0.156% vs desktop 0.045%; English mobile 0.064% vs desktop 0.019%). Audio CTR was 1.911% in May but fell to 0.119% in June on small denominators (≈1800 impressions; 5 clicks). Impressions concentrated in expected Texas metropolitan areas (Houston 24.4%, Dallas 19.9%, Austin 7.9%). Phase 2 Google Analytics Behavior Flow showed 55.2% of language-distinguished landings were on Vietnamese pages ( χ ² 1 =6.7; P =.01). Cost efficiency was favorable (CPC US $2.35 and CPM US $1.45). Conclusions A community-engaged bilingual digital campaign produced measurable in-language engagement among Vietnamese American audiences in Texas. Like other COVID-19 outreach campaigns directed at historically marginalized groups, researchers worked closely with CBOs, paying particular attention to messaging, language translation, and graphic representation in display, audio, and video advertisements to reach the population of interest. What differed from other campaigns was the use of DV360 allowing dissemination across multiple platforms and devices. Results are limited to engagement because direct impact on COVID-19 immunization or participation in clinical trials was not measured. Future directions can explore more clinically significant outcomes, in-language radio advertising, and harnessing AI to develop and monitor public health campaigns.