The COVID-19 pandemic will hit the world’s most vulnerable people the hardest including the one billion people living in informal settlements and slums worldwide. These areas are densely populated with inadequate household water and sanitation, little or no waste management, overcrowded public transport and limited access to formal health care facilities. In addition, they suffer from a lack of basic services, secure tenure and adequate housing. Urgent preparations are needed now to enable residents to stay safe and healthy.