The Scottish Government will now send out white, windowed envelopes after a supply issue for blue ones.
The 'distinctive' blue envelopes have been given priority by Royal Mail and will start arriving through letterboxes from Monday.
Professor Leitch made the comments as Covid-19 vaccines are scaled up around the country,
The Oxford University/AstraZeneca vaccine has become the latest coronavirus jab approved for use in the UK.
Jab given the green light by the Medicines and Healthcare products Regulatory Agency following clinical trials.
The Pfizer/BioNTech jab will begin to be distributed across Scotland from Tuesday.