I correct myself. This as such is just an organization that tries to keep a control group of unvaccinated people, which, for scientific reasons, does make sense. If you donate them some money for it, your decision. But I see no hint that this card would have any legal impact. If you work in some place/profession that requires you to be vaccinated (e.g, as of now, medical personel in france), this card won't help you avoid it. And of course, in no way would it safe you from regular tests, if these are required in your country.

This as such is just an organization that tries to keep a control group of unvaccinated people, which, for scientific reasons, does make sense. If you donate them some money for it, your decision. But I see no hint that this card would have any legal impact. If you work in some place/profession that requires you to be vaccinated (e.g, as of now, medical personel in france), this card won't help you avoid it. And of course, in no way would it safe you from regular tests, if these are required in your country.

Edit after comments

It's indeed questionable whether in this case even the study or the concept of the study actually exists. Normally, the study subjects don't pay for the study, nor are they donating (except their time and body). The website may, strictly speaking, not doing something illegal, but it does sound like a rip-off.