I believe you can't ever get cleared. The only way to confirm mad cow is to dissect the brain, so obviously it can't be tested for in a living person. As a result, anyone with over a certain amount of risk for mad cow can never be allowed to donate.

If I had leukemia, I'd love some possibly-mad-cow-tainted blood/marrow from an otherwise healthy donor.

:-) I am the UK kidney transplant list last year I turned down a potential kidney as there was a risk that the donor was potentialy HIV+

The surgeons second line was "don't worry we have really good drugs for HIV these days"

In the end we agreed that given my age and I then had fairly good function left that letting some on else have it was for the best

You can still donate (blood, at least) for research purposes, if you can find someone who's collecting it. Bonus, you get $50–100 instead of a cookie!

It's still a thing, see: http://www.redcrossblood.org/donating-blood/eligibility-requ...

I lived in Germany for three years in the '00s so I'm ineligible.

I lived in Germany in the mid 80s (military brat) and I also have always been told that I can't donate because of that.