This dataset contains information on seven prospective cross-sectional nationwide residual sera collection rounds. The samples were analyzed for IgG antibodies against S1 proteins of SARS-CoV-2 with a semi-quantitative commercial ELISA (EuroImmun, Luebeck, Germany). We provide a CSV file containing the following variables: code : unique sample code age_cat : age categories by 10-year age bands (0-10, 10-20, ..., 80-90, 90-Inf), the lower limit is included, e.g. 0-10 = [0,10) sex : sex (f = female, m = male) province : province of residence (11 categories) region : region of residence (3 categories: Brussels, Flanders, Walloon) collection_round : collection round (values 1 to 7) collection_start : start date of the collection round collection_end : end date of the collection round igg_orig : measured IgG OD value as character (note, a semi-quantitative ELISA was used, i.e. this should not be interpreted continiously) igg_cat : categorized IgG OD values LoD : IgG OD < 0.15 negative : 0.15 ≤ IgG OD < 0.8 ... : Please cite: Seroprevalence of IgG antibodies against SARS coronavirus 2 in Belgium – a serial prospective cross-sectional nationwide study of residual samples (March – October 2020) Herzog Sereina, De Bie Jessie, Abrams Steven, Wouters Ine, Ekinci Esra, Patteet Lisbeth, Coppens Astrid, De Spiegeleer Sandy, Beutels Philippe, Van Damme Pierre, Hens Niel, Theeten Heidi. medRxiv 2020.06.08.20125179; doi: https://doi.org/10.1101/2020.06.08.20125179 ...