Abstract Issue/problem COVID-19 vaccination rates remained below 50% in Moldova, North Macedonia, and Serbia, especially among vulnerable populations like pregnant women and those with chronic diseases. This was strengthened by a lack of targeted communication and training for healthcare workers, and COVID-19 fatigue. Strategies to increase vaccine demand and confidence are a global priority, especially among vulnerable populations. Description of the solution From May 2022 to April 2024, the USAID MOMENTUM Routine Immunization Transformation and Equity project employed behavior integration to design a social and behavior change strategy, centering on vaccination as a part of a healthy lifestyle. It was implemented through continuing medical education (CME) and community engagement (CE) workshops with vulnerable populations, supplemented by cross-country learning exchanges. The outcomes provide a framework for public health initiatives aimed at boosting vaccine uptake through innovative, behavior-based methods. Results 1,618 healthcare professionals, able to reach 2.5 to 4.8 million patients, received training in immunization, COVID-19 vaccines, and quality health service, and 99% indicated confidence in applying the knowledge. 265 CE workshops, engaging 4,079 patients, increased awareness and addressed concerns related to vaccination. Of 3,223 patients who were followed up, 47% reported setting an appointment with their doctor regarding vaccination, 27% discussed vaccination with their partners, and 7% proceeded to receive the COVID-19 vaccine. Lessons Behavior Integration helped address key barriers to vaccination and informed the design of strategies (i.e. situating COVID-19 vaccination as part of a healthy lifestyle). Establishing trust with healthcare providers and patients through collective engagement improved health behaviors. Focusing on health as a wider priority helped re-establish the significance of vaccination as part of a healthy lifestyle. Key messages • Behavior science and behavior integration helped identify and address barriers, as well as design tailored interventions to improve vaccination demand and confidence. • Collective engagement, focused on integration of COVID-19 vaccination as part of a healthy lifestyle, achieved results through addressing vaccine hesitance from both sides of the equation.