従来の抗体検査ではかなりの見落としがあって
実際の感染は遥かに拡がっていた可能性
https://www.bmj.com/content/370/bmj.m3364
>A recent seroprevalence survey of 1473 residents
>(79% of the local population) in Ischgl, Austria,
>using a combined IgG and IgA approach found
>SARS-CoV-2 antibodies in 42.4% of those tested,
>far higher than rates in previous population
>based surveys of other infection hotspots.

>Similarly, IgA antibodies were detected in 11% of 1862 people
>sampled from the general population in Luxembourg,
>whereas IgG antibodies were found in only 1.9%.