Abstract

Introduction: The COVID-19 vaccination significantly mitigated the global health crisis, demonstrating the impact of scientific innovation and international collaboration. However, vaccination uptake remained uneven due to complex psychological, cultural, and structural factors. This study explored adult experiences and perceptions along the COVID-19 vaccine acceptance-hesitancy continuum in Chile, identifying barriers and facilitators among both Chilean nationals and international migrants. Methods: A multiple case study design was conducted. Using snowball sampling, 67 adult participants (31 Chileans and 36 international migrants) were recruited across three large urban settings in the country. Semi-structured online interviews (60-90 min) were audio-recorded, transcribed verbatim, and analyzed using thematic approach. Fieldwork spanned from January 2023 and April 2024 with institutional ethical approval. Results: Findings revealed generally positive views of the national vaccination plan, though levels of health literacy varied notably. Five key drivers of hesitancy emerged: perceived experimental nature of the vaccine, side effect concerns, preference for natural prevention, government distrust, and conspiracy beliefs. Many participants initiated the vaccination series but did not complete the full schedule. Barriers included misinformation, logistical challenges, and institutional mistrust. Conversely, facilitators involved workplace access, community responsibility, and inclusive practices for migrants. Discussion: Addressing the diverse explanatory frameworks behind vaccine reluctance requires targeted communication strategies tailored to socioeconomic profiles, informational needs, and cultural contexts. Culturally responsive education, improved provider-patient communication, and structural reforms are critical to ensure equitable vaccine access, particularly for marginalized populations. Tackling the identified barriers demands a multifaceted strategy-one that integrates health education, respectful clinical interactions, and structural reforms aimed at guaranteeing universal access to immunization services.