• Young children and older populations both experienced significantly lower seroprevalence in comparison to other ages (Table 1). These preliminary findings from ages 5-9 suggest young children are infected less than older populations, as has been supported by similar studies.
• Uncertainty whether lower seroprevalence in older population was attributed to social distancing or lower development of IgG response
• The seroprevalence increased from 5% to 11%, which was expected since the peak in the region was reached the week before the study began in addition to the increase of cumulative cases over time
• As Switzerland approaches the end of the first wave of COVID-19, the low presence of IgG antibodies suggest the majority of the population presents little immunity to SARS-CoV-2.

Limitations

• Analyses included randomly selected participants AND household members
• Recruitment method (first by email and then by postal mail to reduce bias)
• Study population excluded children under age 5
• ELISA test was only validated in the adult population and it was not conducted using the standard plaque reduction neutralization
• Selection bias potentially accounting for overestimation of prevalence