In Germany, a consortium of authority-accredited laboratories (ALM)covered about 90% of all SARS-CoV-2 PCR tests during the `Corona era'(March 2020 until January 2023), and they likewise conductedserological mass tests for IgG antibodies until May 2021. We analysedthese ALM-observed time courses of PCR and IgG tests,their respective test-positive fractions in particular. We found thatthe week-resolved time course of the IgG-positive fraction can bewell reproduced by the cumulative sum of the preceding, likewiseweek-resolved, PCR-positive fraction values. For this, just onemultiplier (0.14) had to be fitted, which means that only 14% ofthose who where tested PCR-positive actually got infected bySARS-CoV-2. For a second analysis, we took the ratio 1:10 between onepositive PCR test and the corresponding number of actuallySARS-CoV-2-infected persons, which is documented in the literature asspecific for Germany, and estimated the time course of the latterwithin the German population. At the end of 2021, the courses ofIgG-positive and infected fractions align well with the IgG-positivefraction (92%) reported by the Robert-Koch-Institut (RKI). At thebeginning of the SARS-CoV-2 mass vaccination campaign on 27/12/2020, aquarter of the German population already carried IgG antibodies fromnatural infections in their blood. This fact must have been known tothe authorities and questions the urgency with which the vaccinationcampaign was propagated.