Nucleic acid (PCR) and antibody (IgG) tests: the course of SARS-CoV-2 infections in the German population unveiled

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 conducted
serological mass tests for IgG antibodies until May 2021. We analysed
these ALM-observed time courses of PCR and IgG tests,
their respective test-positive fractions in particular. We found that
the week-resolved time course of the IgG-positive fraction can be
well reproduced by the cumulative sum of the preceding, likewise
week-resolved, PCR-positive fraction values. For this, just one
multiplier (0.14) had to be fitted, which means that only 14% of
those who where tested PCR-positive actually got infected by
SARS-CoV-2. For a second analysis, we took the ratio 1:10 between one
positive PCR test and the corresponding number of actually
SARS-CoV-2-infected persons, which is documented in the literature as
specific for Germany, and estimated the time course of the latter
within the German population. At the end of 2021, the courses of
IgG-positive and infected fractions align well with the IgG-positive
fraction (92%) reported by the Robert-Koch-Institut (RKI). At the
beginning of the SARS-CoV-2 mass vaccination campaign on 27/12/2020, a
quarter of the German population already carried IgG antibodies from
natural infections in their blood. This fact must have been known to
the authorities and questions the urgency with which the vaccination
campaign was propagated.