[KittyKares]

As far as I can tell from the Red Cross website, they are not blocking vaccinated people from giving blood:

https://www.redcross.org/about-us/news-and-events/news/2021/what-you-need-to-know-about-covid-19-vaccines-and-blood-donation.html

[Sacajaweau]

I just don’t know...Do the antibodies show up in the blood?

[RideForever]

As far as I can tell from the Red Cross website, they are not blocking vaccinated people from giving blood:

Further down in the source you gave you will find this -

Individuals who have received a COVID-19 vaccine are not able to donate convalescent plasma with the Red Cross.

However, these individuals may be eligible to donate other blood products with the Red Cross including whole blood and platelets if they meet other donation eligibility criteria.