It’s nowhere near that dramatic - how many of the 5m want to travel - soon - to the few countries that aren’t accepting it ? Loads of countries have already confirmed they’ll accept it. At the time there was no reason to believe it wouldn’t be ok - it’s the same vaccine as administered under...
Here’s the official Malta position if it helps
https://deputyprimeminister.gov.mt/en/health-promotion/covid-19/Pages/travel.aspx
Which includes (the bit in bold was added when they agreed to accept the imported batches):
A valid vaccination certificate recognised by the Superintendent of...
Three batches of Indian-imported vaccine (AstraZeneca) are not EU approved but are UK approved - so certain EU countries have decided not to accept them. If you received one or two doses from those batches you risk not being able to gain entry to wherever you are travelling (actually the more...
Malta initially were refusing but quickly backtracked and are now accepting it
Portugal backtracked (unofficially) yesterday, waiting for confirmation
https://www.mylondon.news/lifestyle/travel/heathrow-gatwick-13-countries-wont-21210824