That’s true, but it’s because at the time the only way to become acclimated was to catch yellow fever, which meant running a substantial risk of dying or severe

That’s true, but it’s because at the time the only way to become acclimated was to catch yellow fever, which meant running a substantial risk of dying or severe disease. In the 21st century we have safe vaccines so if someone is not “acclimated” or immune to a virus, they can gain the status easily via a free and safe vaccine. This removes the problems. In any case, the discussion here is not about immunity passports themselves. It’s about whether only a vaccine should count, or if proof of natural infection should also count as equivalent to a vaccine record.