In Ecuador, the health emergency caused by COVID-19 required the State’s concerted effort to provide safe, effective, and free vaccines. At the start of 2022, the country reached broad vaccination coverage, placing it among the countries in the Americas with the strongest achievements in this area. To systematize and analyze the lessons learned from the introduction of the COVID-19 vaccine, the country and the Pan American Health Organization/World Health Organization (PAHO/WHO) implemented an intra-action review (IAR) during the application of the measures adopted, which presented the lessons learned and corrective measures to strengthen the deployment of vaccination. This article describes, based on the authors' experience and the results of the IAR, the introduction of vaccination in Ecuador, the timely response mechanisms, and the difficulties encountered in deploying vaccination in accordance with the national plan and in achieving the proposed objectives.