The previous result would not make a difference (even though it should mean that you would be OK to board if you have a recovery letter). It is my understanding that whether you have previously tested positive or not, and even if you have recovered, in the unlikely event of a new positive result on the day of boarding that would be a problem for Azamara. My previous positive test result from April is not linked to a passport number, but I don't think that matters. If I test positive on the day of embarkation, I would acknowledge the previous positive test result and recovery, and present the recovery letter, but I don't expect it would help.