Serosurveys for Coronavirus Disease 2019 (COVID-19) aim to estimate the proportion of the population that has been infected by and developed antibodies against SARS-CoV-2, the virus that causes COVID-19, at various points in time. In this presentation, we will outline the key findings of the Ontario COVID-19 serosurveys performed by Public Health Ontario (PHO) and discuss the interpretation of our results, as well as the implications of the findings on the pandemic response.