We have used the electronic card sent out by our state health department In our phones wallets and acceptable to Princess on all 4 cruises we took last year. I also have it in writing from Princess. The original cards are flimsy and easily lost or destroyed. The bigger issue being asked by the OP is about unvaccinated passengers. Those rules will change cruise to cruise and could change at a moments notice. There are people who will not vaccinate and do not want to take tests. On cruises with certain ports they will have a major problem