Fig. 2.

SARS-CoV-2 incidence at study sites and study design. a. Number of SARS-CoV-2 infections/100,000 inhabitants in the participating cities/counties from calendar week 14–53 in 2020. The B-FAST study period is highlighted in grey. b. B-FAST study design in which swabs were taken from an entire class several times per week (Monday, Wednesday and Friday (shown) or Monday and Thursday). Swabs were pooled and tested by RT-qPCR. Detection of a positive pooled test (red dot) triggered individual testing of the entire class by RT-qPCR and subsequent identification of a single or several positive individuals who were quarantined. The remaining students continued with school lessons and scheduled pooled testing (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.).