I built the national covid health information system (NCHIS) for my country that helped to mitigate the pandemic. It streamlined the sample collection to issuing reports and aggregated data nationwide and generated reports for government to make decisions on lockdowns and track the pandemic progress.
Well this was not completely built by me but I got help from 20 odd university students but I overlooked the project and did lot of coding myself. Even though it’s not used now since the pandemic has settled I’m happy what I have done.