PMC

Hypothetical antibody level distribution before exposure (left) and after exposure (right).

Histograms of IgG (a), IgM (b) and titre score (combination of IgG and IgM) (c) for highly exposed, less exposed and general population. The vertical line gives the manufacturer’s cut-off value for seropositivity.

Estimated distribution of titre score in highly exposed, less exposed and reference subjects when assuming the minimum fractions of infection as estimated (non-parametric) in the . The curves are estimated by taking the distribution of titres of those in area C of (non-parametric method) and smoothing this distribution.

Cumulative difference of the proportion with a certain titre score (combination of IgG and IgM) in the highly exposed and the general population. Wavy line: crude data; black line: the smooth version thereof; grey line: calculated by first fitting log-normal curves to  c. The dashed lines indicate the top of these curves.