When Turkey was taken off Britain’s red list for travel last month, Sally Morrow, an English expatriate living in Ankara, rushed to her computer and booked flights to London, so that she could reunite with her ailing parents after more than six months apart.

But soon after her ticket confirmation came through, Morrow, 47, read that the certificate she received when she was vaccinated in Turkey — with the Pfizer coronavirus vaccine — would not be accepted in Britain. As a result, Morrow would be required to quarantine for 10 days and have at least three negative coronavirus tests before being permitted to leave isolation there.

"I had the Pfizer jab, the Rolls-Royce of vaccines, the exact same one as millions of Brits, yet I’m considered unvaccinated simply because I got my vaccine abroad,” Morrow said.