With regards to this topic, there seems to be a number of known unknowns never mind the unknown unknowns that the past year has often generated. With there being little to no job security throughout the ME, it makes sense to try and ensure that your credentials are in order, should the worst happen. Blood tests may not even be required to verify what vaccine you had if personal vaccine data is held electronically and is made accessible to multiple countries and potentially to multiple organisations as well. As aircrew, it would be hard to avoid having to participate in such a system. Despite the concerns regarding personal data protection, it seems that these are being overshadowed in Europe at least by the desire to open up borders. However it still remains to be seen how this will develop.
It’s also not outside the realms of reality that certain counties will require vaccination in lieu of any quarantine period but specific vaccines will only be accepted. The Cypriots have pledged to open their borders for tourists from May but vaccines that are approved by the EMA will only be accepted. Given how cautious Oz and NZ have been throughout the pandemic then I wouldn't be surprised if they only recognise selected vaccines. The TGA in Oz have already remarked to the press that vaccine trial data from China and Russia is rather limited. Will we see Aussies and Kiwis with the ‘wrong’ vaccine still having to sit in a hotel for close for two weeks?
I am sure these potential hurdles will fade into insignificance over time, as the effectiveness of each vaccine becomes apparent. Vaccines from China and Russia may prove to be very effective but determining that will take time to establish. Until that point is reached, I suspect not every country will open its doors to travellers with just any vaccine.