Objective: In response to the urgent need for COVID-19 vaccination clinics for ^{vulnerable populations in Kentucky (12.2% live in poverty; 5.6% lack healthcare coverage),} nurse leaders received training through a standardized training program to prevent COVID-19 vaccine administration errors (VAE). This project aimed to evaluate the process effectiveness of the training program as perceived by the trainees (Team Leaders) and to assess the number and types of vaccination errors that occurred during mobile vaccination clinics during the mobile clinics in Kentucky. Design: A program evaluation. Sample: A total of 12 Nurse Team Leaders underwent the standardized training program. Measurement: The Logic-Model-based, 7-item, 4-point Likert scale (α=. 84) was used to evaluate training effectiveness. VAE rates were calculated. Intervention: The Kentucky Nurses Association (KNA) developed a standardized COVID-19 vaccination training program for Team Leaders to prevent VAE during the mobile clinics. Components of the training program (program development, training protocols, and error monitoring) were based on the CDC’s (2022) recommendation that all healthcare providers need to know how to store, handle, prepare, and administer each COVID-19 vaccine product. Results: Team Leaders strongly agreed on the effectiveness of the training (e.g., the importance of training, staying updated, and feeling prepared). VAE was 0.001% (9/8086 administrations over 16 months). Conclusion: Findings suggest that the training program successfully prevented vaccination errors, and that Nurse Team Leaders collectively perceived the training program as effective. Widespread adoption of similar programs is recommended to prevent VAE during public health emergencies, including future pandemics.