There are serious issues with vaccine passports, especially as it will take until 2022 for some parts of the world to even receive the vaccines (since other more well off countries bought the majority of production capacity). Then add in the folks who just can't get it for disability/illness reasons, and that's a lot of exclusion and access barriers. I prefer the need for a quarantine when traveling and wearing masks until herd immunity has been achieved, although the hotel quarantine the UK is implementing is expensive and will likely keep people from being able to return home. (unless they have financial assistance for it? I haven't seen that mentioned but I also haven't dug too far.)