Sorry, I think I was unclear! This is a rule only for those in the trial. If I donate blood today, having had the vaccine, and the blood donation service check

Sorry, I think I was unclear! This is a rule only for those in the trial. If I donate blood today, having had the vaccine, and the blood donation service checks my blood for antibodies and informs me that I had COVID-19 (or so they think!), then I will have been unblinded in the trial which isn't allowed. This isn't the case for the general population. I'm also not allowed to take part in any other antibody tests that might accidentally unblind me in the trial.