Why not just get a covid antibodies test first?

Chicago IL

Description

It is now known that if one has already had covid once that they have developed antibodies and are unlikely to benefit from vaccination. With that, why don't we all just get a covid antibodies test first before running out to get potentially-lethal experimental mRNA gene therapy shots that have already killed 1000's? If you sign up to donate blood in your area, they will give you a free covid antibodies test. https://www.medrxiv.org/content/10.1101/2021.06.01.21258176v1