It comes after Scots in the 60 to 64 age group voiced fears they would be “forgotten about” by the vaccine rollout after First Minister Nicola Sturgeon announced 55 to 59 year olds would begin receiving a first dose next week.
Many later took to social media to say they had called the national vaccine helpline to be told that they had an appointment already scheduled, but had not yet been notified of it due to issues with the appointment letter system.
"No letter, but phoned and there was an appointment already booked for myself and my husband in Grampian,” one said.
Professor Eleanor Riley, 64, immunologist at Edinburgh University, said she had called the vaccine helpline after not receiving an appointment letter, only to be told that she already had an appointment booked for next week.
The national vaccine helpline can be reached on 0800 030 8013.
Edinburgh-based Dr Jim Jarvie urged all those aged 60 to 64 who have not received a letter to call the NHS Lothian vaccine helpline on 0300 790 6296, after being told he already had an appointment despite not having been notified.
Ms Sturgeon said she would investigate the issue on Tuesday after Labour MSP Jackie Baillie reported 70 missed vaccination appointments in one day at a centre in her constituency of Dumbarton, and asked if this was due to a lack of notification letters.
Ms Baillie added that some 50-year-olds in her local area had been called for vaccination, while others over 60 had not.
Asked by Conservative MSP Miles Briggs when those in the 60 to 64 age group in Edinburgh could expect to receive a vaccine, Ms Sturgeon said on Thursday that there may be some overlap between age groups.
"If we were to work through people in a strictly chronological order and to not start vaccinating, for example, 55 to 59-year-olds until we had completed vaccinating 60 to 64-year-olds [...] we would not be using vaccines as quickly as we could,” she said.
"Vaccines would be sitting on the stocks if we took that approach. We are taking the approach that we are taking to get to people as quickly as we possibly can.”
A spokesperson for NHS Lothian said the Scottish Government is responsible for vaccine appointment notification letters.
The Scottish Government was approached for comment.