Widespread public vaccination is one of the effective mechanisms to ensure the health and prevent deaths in societies. The coronavirus disease 2019 (COVID-19) vaccine is a stark instance in this regard. Vaccine development is a complex process requiring firm-level capabilities, various infrastructures, long-term planning, and stable and efficient policies. Due to the global demand for vaccines during the pandemic, the national capability to produce vaccines is critical. To this end, the current paper investigates influential factors, at the firm- and policy-level, in the COVID-19 vaccine development process in Iran. By adopting a qualitative research method and conducting 17 semi-structured interviews and analyzing policy documents, news, and reports, we extracted internal and external factors affecting the success and failure of a vaccine development project. We also discuss the characteristics of the vaccine ecosystem and the gradual maturity of policies. This paper draws lessons for vaccine development in developing countries at both firm and policy levels.