The article presents a population-based study, SEROCOV-POP, conducted in Geneva, Switzerland, to estimate the seroprevalence of anti-SARS-CoV-2 IgG antibodies. The study aimed to assess the burden of COVID-19 by measuring infection rates and monitoring the epidemic progression. Participants were randomly selected from the Bus Santé study, a representative sample of the Geneva population, and their household members. The study used a Bayesian logistic regression model to estimate seroprevalence, adjusting for test performance and demographic factors. Results showed that between April 6 and May 9, 2020, the seroprevalence increased from 4.8% to 10.8%, with a significant increase in the second week. Young children (5-9 years) and older adults (65+ years) had significantly lower seroprevalence compared to those aged 20-49 years. The study estimated that for every confirmed case, there were 11.6 infections in the community. These findings highlight that most of the population in Geneva remained uninfected during the pandemic, suggesting that the epidemic is not yet under control due to a large susceptible population. The study also provides insights into the immunological state of the population, which is crucial for public health decision-making.The article presents a population-based study, SEROCOV-POP, conducted in Geneva, Switzerland, to estimate the seroprevalence of anti-SARS-CoV-2 IgG antibodies. The study aimed to assess the burden of COVID-19 by measuring infection rates and monitoring the epidemic progression. Participants were randomly selected from the Bus Santé study, a representative sample of the Geneva population, and their household members. The study used a Bayesian logistic regression model to estimate seroprevalence, adjusting for test performance and demographic factors. Results showed that between April 6 and May 9, 2020, the seroprevalence increased from 4.8% to 10.8%, with a significant increase in the second week. Young children (5-9 years) and older adults (65+ years) had significantly lower seroprevalence compared to those aged 20-49 years. The study estimated that for every confirmed case, there were 11.6 infections in the community. These findings highlight that most of the population in Geneva remained uninfected during the pandemic, suggesting that the epidemic is not yet under control due to a large susceptible population. The study also provides insights into the immunological state of the population, which is crucial for public health decision-making.