It could take years to get the answers to many questions about the Covid 19 vaccine.
The first polio vaccine was invented in 1953 and the disease has yet to be fully eradicated (cases still show up in Pakistan and Afghanistan.)
The first smallpox vaccine was invented in 1796 and the WHO finally said smallpox was eradicated in 1980.
I agree that mask wearing, social distancing and washing hands will be important to do for a very long time. (I've put face masks on my packing list. A small bottle of hand sanitizer is in my 3-1-1 bag.) But how long do we wait to open our borders and help our economies? Until Covid-19 is fully eradicated? Until we have a vaccination that proves 100% that people can't get it and can't carry it?
Nothing is 100% certain. You could get on a plane and head to your favorite destination and not make it. There is no guarantee that the plane will arrive.
The question has to be asked: Do countries close their borders for years until we get as close to perfect or do you minimize your odds against problems? Is it really better to keep out a fully vaccinated visitor from North America than to allow a non-vaccinated European into your country?
Remember, it is impossible to fully close a country. Goods still have to arrive. (People like to eat.) Who's to say a ship's crewman or truck driver or even a member of a flight crew isn't carrying the virus without symptoms? They can then easily pass it on to someone they come in contact with and it can spread again.
It also doesn't mean that if a country opens up it is a good idea to visit that country. If vaccination rates are low and cases are high, perhaps waiting would be advisable.
There is no perfect system. There are no documents that can't be counterfeited. You do what you can to minimize damage.
Every person has to decide for themselves what it acceptable for travel and what isn't.
If you are waiting for the day that masks and social distancing are no longer required for travel, well, you might as well sell your bags. You're not going to be traveling for a long time.