Fig. 3

For sensitivity and specificity adjusted (left) and unadjusted (right) SARS-CoV-2 sero-prevalence over the follow-up period. The 95% confidence intervals for the weekly sero-prevalence were based on the 2.5 and 97.5 percentiles from 5000 repetitions of a cluster bootstrap that accounts for within household clustering. The estimates do not account for sample weights. The estimation without accounting for within-household clustering but considering sample weights produced similar trends (Additional file 1: Figure S1). A slight increase of sero-prevalence is indicated from the first to the fourth week of follow-up. The huge increase from week 4 to weeks 5–11 has to be taken with caution, as during these weeks, participants with intermediate results in the DBS (of whom 50% turned out to be positive in plasma sampling) were be retested by plasma-sampling during this time interval. The upward trend without these participants is shown in Additional file 1: Figures S1 and S2