All people over 18 in Scotland will be able to book a Covid booster vaccine from today.
Appointments for the 18 to 29 age group can be booked through the online portal from 10am.
Those who received their second dose 12 or more weeks ago will be able to get their booster jab.
The Scottish Government is aiming to offer all adults a booster slot by the end of the year amid rising Omicron cases.
Early studies have shown that a third dose will help prevent around 75% of people getting any Covid symptoms.
On Monday, the booster vaccination programme was extended to the 30 to 39 cohort, with everyone in that age group asked to book an appointment.
Walk-in centres
All NHS Grampian vaccination centres are offering walk-in boosters for citizens over the age of 40 on Wednesday.
Those attending a walk-in are reminded that they may face a longer wait and could be asked to return at another time if the centre is busy.
All Aberdeenshire clinics have been offering walk-in vaccines for first, second and third doses since Monday.
Meanwhile, Aberdeen centres have required people of all ages to book an appointment in advance. Those planning to visit later in the week should check if walk-ins are running each day.
The Fiona Elcock Vaccination Centre in Elgin is also now operating a walk-in service for anyone 40 or over.
It will be open between 10.30am and 5pm from Monday to Friday
Booster vaccine appointments can be made by calling 0800 030 8013 or via the online booking portal.