F1's regular medical car driver will not be permitted into some of the countries set to host the final grands prix of 2021.
In Turkey, the official medical car occupants Alan van der Merwe - the driver - and Dr Ian Roberts had to sit out the race after testing positive to covid.
But in the days afterwards, South African van der Merwe went public to reveal that he is not vaccinated and therefore may have to skip several more races.
"From what we understand, there are a couple of countries where you will probably not be allowed to enter unless you are vaccinated," F1 race director Michael Masi now confirms.
"From that perspective, the FIA obviously has to respect the requirements of each country that we visit, which includes all of the teams and everybody else."
It is believed van der Merwe will therefore have to sit out the forthcoming Qatar, Saudi Arabia and Abu Dhabi grands prix.
He and Dr Roberts were replaced in Turkey by Formula E's regular medical car crew.
"Both Alan and Ian were available all weekend on the other end of the phone to help Dr Franceschini and Bruno Correia with their acclimatisation to this role," said Masi.