At the time of this paper, Pakistan had the third highest population of zero-dose children globally. Electronic census-based immunization information systems can help to register and track individual's immunization status, as well as that of the community, while also helping to improve EPI logistics and eventually improve population estimates and vaccine targets. This article describes the implementation of an electronic immunization information system in the Sindh province of Pakistan that was part of a larger, intensive intervention that included a community micro-census and registration of all pregnant women and children in eight districts, as well as immunization promotion and microplanning. It also discusses the results at the end of the 18-month intervention period and recommendations for future enhancements of the system.