This invited talk describes the work that a multi-disciplinary team of 20+ volunteer scientists did between March of 2020 and April of 2022, working very closely with the Presidency of the Valencian Government to support their decision-making during the COVID-19 pandemic in Spain. This team was known as the Data Science against COVID-19 taskforce. The team's work was structured in 4 areas: (1) large-scale human mobility modeling; (2) development of computational epidemiological models (metapopulation, individual and LSTM-based models); (3) development of predictive models of hospital and intensive care units' occupancy; and (4) a large-scale, online citizen surveys called the COVID19impactsurvey (https://covid19impactsurvey.org) with over 720,000 answers worldwide. This survey enabled us to shed light on the impact that the pandemic had on people's lives during the period of study [3,4,5]. In the talk, I will present the results obtained in each of these four areas, including winning the 500K XPRIZE Pandemic Response Challenge [1] and obtaining a best paper award at ECML-PKDD 2021 [2]. I will share the lessons learned in this very special initiative of collaboration between the civil society at large (through the citizen survey), the scientific community (through the Data Science against COVID-19 taskforce) and a public administration (through our collaboration with the Presidency of the Valencian Government). For those interested in knowing more about this initiative, WIRED magazine published an extensive article describing the story of this effort: https://www.wired.co.uk/article/valencia-aicovid-data
