I'm noticing that certain countries, eg. the uk, have different rules for vaccinated/unvaccinated visitors. can anyone who has traveled internationally in europe lately shed some light on how vaccine status is checked upon arrival? do they require you to show some form of proof that you have taken all x vaccines? what does this proof look like? does every country really provide their citizens with this form of documentation, and do they actually go through the trouble of looking at these documents upon arrival?