Scots continue to be urged to get a third dose of the Covid jab to help protect against the virus.
Eligible adults and some groups of children are considered to be 'fully vaccinated' after receiving all three doses of a coronavirus vaccine.
Getting the booster helps to increase levels of protection against the virus as immunity begins to wear off after doses one and two of the jab.
Scots must wait 12 weeks between dose one and two and then again between doses two and three.
But why do we need a booster?
Why do we need a third dose of the Covid jab?
A booster jab tricks your immune system into thinking that it is again receiving a pathogen - an organism that can produce disease - so antibody producing cells are again recalled into gear.
In turn, the third dose gives you protective for longer and help prevent you from becoming seriously ill if infected with Covid.
This is because the third dose results in the quantity and quality of antibodies that are produced to increase.
This process is called antibody affinity maturation.
It sounds pretty complicated but in simple terms this means that immune systems learn to do a better job when faced with Covid cells as antibodies can tackle the virus more efficiently.
In addition to this, affinity matured antibodies can be more effective when faced with Covid variants with multiple mutations.
The mutated strains are made up differently and therefore can be more immunity resistant if you become infected.
Boosters help to tackle this.
According to Scottish Government data, 3,366,018 eligible Scots have received a third dose or booster.
Blue appointment letters are being sent to hundreds of thousands of Scots who haven't yet had their covid booster jab.
Who can get a Covid booster dose?
According to the NHS, everyone aged 16 and over who has had two doses of the Covid vaccine at least three months ago is eligible for a booster dose.
Some children between the ages of 12 and 15 can also get boosted if they fall into the 'high risk' category or live with someone considered high risk or who has a weakened immune system.
You can get more information on 'high risk' groups here.
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