Tests are unreliable and even when accurate only reflect the viral load when the test is taken.If Nan Daphne, who got her second jab in Feb, wants to visit me in August and has a vaccine passport; can you or anyone assure me she can't carry or pass on Covid?
If my preggers missus tests negative in June, tests negative for Covid, and wants to take a trip back to the UK, who is more of a "threat to society"?
Can we even answer these questions with any degree of certainty in order to discriminate to that degree? Hmmmmm......
A vaccination passport will provide far more certainty even if not 100% protection.