Youths living in crowded impoverished urban areas face higher risk of infection by SARS-CoV-2 . This article presents lessons learned from a preventive intervention project intersected by the COVID-19 crisis that moved from a mix-methods study design to online ethnography . The 'home-officed' research team e-witnessed high-school students' daily lives and collaborated in youths' and community-based organisations' responses in the territories where they study and live . Psychosocial distress increased, also driven by the disastrous governmental response to the health and economic crises . There was growing anxiety about meeting friends and dating, with structural limits for sustaining the recommended social distancing, which added to gender/sexuality-based violence . Simultaneously, we observed students becoming relevant actors through co-producing preventive practices, surpassing risk-group notions and combining SARS-CoV-2 prevention with sexuality, gender, racism and mental-health issues . They managed internet-mediated applications to promote critical thinking and collective actions aimed at health promotion among their peers, from their homes . Freire's concept of 'untested-feasibility' fostered researchers', students' and community leaders' imaginations in the face of this unprecedented crisis, thereby enhancing social responses to the epidemic to become rights-based comprehensive dialogical preventive activities . This ongoing intervention-research stresses how prevention sciences can go beyond reduction of this pandemic to a viral event.