This project addressed the critical issue of non-vaccination, under-vaccination, and late vaccination in Bangladesh, particularly among marginalized communities such as residents of urban informal settlements, climate internally displaced persons (IDPs), peri-urban/rural residents, and Forcibly Displaced Myanmar Nationals (FDMNs). By collecting and analyzing data in the Teknaf/Cox’s Bazar region and in urban informal settlements in Dhaka, the project identified current vaccination rates, the timeliness of vaccinations, and the factors contributing to vaccine hesitancy and delayed acceptance. The study provided insights into vaccine decision-making behaviors and barriers within these communities, informing strategies to improve vaccination rates. The ultimate goal was to enhance public health programming and policy to reduce morbidity and mortality associated with vaccine-preventable diseases like polio, measles, COVID-19, cholera, and HPV. This project contributed to achieving vaccine equity, particularly in marginalized populations, and provided a foundation for further research and interventions aimed at improving health outcomes in Bangladesh.