Abstract Since late 2020, vaccination sites have emerged rapidly in order to protect the population against COVID-19. Health services in Montérégie (Québec) are provided by three organizations. Each adopted a different approach to immunization. The Regional Public Health Department took this opportunity to describe, compare, and explain these three approaches. A mixed methods design through a multiple case study was conducted. Users, employees and managers were interviewed at the end of 2021 on several performance-related topics. Individual interviews with employees and managers in mid-2022 further explored these topics. 38 managers, 360 employees, and 946 users participated in the survey. 9 managers and 10 employees were interviewed. Most participants were satisfied with vaccination organization regardless of the model used, mainly because of high geographic and temporal accessibility of the sites. Further signage to indicate directions could optimize accessibility. High adaptability was essential for managers and employees. Training strategies such as people to refer to and pairing allowed to better deal with frequent changes and staff rotation. The addition of ongoing training could be beneficial. Rapid changes in employee schedules were identified as a challenge. The use of technology-based scheduling tools, accessible to all, brought added flexibility, which was appreciated. Several ideas were used to communicate updates on a daily basis. However, timely implementation of new recommendations remained an ongoing challenge. Dedicated clinics for specific clienteles were successful. Community partnerships were generally beneficial, although establishing more of them could potentially reach other vulnerable communities. To improve accessibility and minimize health social inequities, a greater investment in local partnerships might reach more vulnerable clienteles. Regular communication and innovative employee support are key elements to improve fluidity of operations. Key messages • Reaching out for vulnerable clienteles is essential to minimize health social inequities. • Rapid changes in services needs underlign fluidity communication importance.