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 borderline: 0.8 ≤ IgG OD < 1.1 positive: 1.1 ≤ IgG OD Please see publication mentioned underneath for more details (https://doi.org/10.1101/2020.06.08.20125179). Funding: This work received funding from the European Union's Horizon 2020 research and innovation program - project EpiPose (No 101003688), the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement 682540 TransMID), the Flemish Research Fund (FWO 1150017N) and from The Antwerp University Fund; which is a community of donors who contribute to research and education with their personal commitment through a donation, gift, bequest or through academic chairs. The funders had no role in study design, data collection, data analysis, data interpretation, writing or submitting of the report. The corresponding author had full access to all the data in the study and had final responsibility for the decision to submit for publication. ; Please cite: Seroprevalence of IgG antibodies against SARS ...