Table 2.

Post-Wave I SARS-CoV-2 seroprevalence data on a large sample collection in general population through outpatients referred to medical lab’s in Belgium in 2020 (reference [5]) and post-Wave II SARS-CoV-2 seroprevalence in blood donors (reference [13]). Last column: estimated no. of cases from seroprevalence data on basis of a 11,4 million Belgian population

Period collection	Median seropositive prevalence (CI95) after wave I	Estimated total no. seroconversions during Wave I
20 to 26 Apr 2020 18 to 25 May 2020 8 to 13 June 2020	5,25% (4,22% - 6,35%) 6,20% (5,05% - 7,31%) 4,74% (3,65% - 5,85%)	$\frac{5,25\%+6,20\%+4,74\%}{3}$*11,4 millions ≈ 540 thousand seroconversions
		Seroconversions during Wave II
First week 2021	18,70% (15,60% - 21,70%)	(18,70%*11,4 millions) – 540 thousand ≈ 1,6 million seroconversions