Nearly 10,000 booster appointments have been missed in the past three days in Edinburgh and the Lothians as NHS bosses urged people to get jabbed before 2022.
NHS Lothian cited low queues and available time slots as a reason for adults to get boosted before January - with more than 76,920 getting jabbed in the run up to Christmas, or 71 per cent of those eligible.
Hopes are high to get another nine per cent of people vaccinated before the countdown into 2022, bringing the total to 80 per cent.
However nearly a fifth of appointments have been missed in the past three days (17 per cent).
Kids aged 12-17 are able to attend drop-in clinics for their second dose if it has been at least 12 weeks since their first dose and they have not tested positive for COVID-19 in the past 12 weeks.
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Pat Wynne, Director of Nursing for Primary and Community Care, NHS Lothian, said: "I would like to thank everyone who has come forward for vaccination so far, every vaccination counts towards making our region safer.
"Getting a booster doesn't mean you won't get COVID-19, but it reduces the chances of it and significantly enhances your protection against serious illness - it could literally save your, or someone else's, life."
NHS Lothian has increased its vaccination capacity hugely in December with the reopening of the Edinburgh International Conference Centre (EICC) in Edinburgh City Centre.
There has been a rise in the number of missed appointments over the festive period, with 17 per cent of people not attending their appointments.
This has resulted in 9,951 available appointments going unused in the Lothian region over Monday, Tuesday and Wednesday (27, 28 and 29 December).
Mr Wynne added: "We know that missed appointments are in part due to the number of COVID-19 cases in the area, which is in turn making people ineligible for their vaccination.
"But it's not the whole story and, if I'm honest, it's a little disappointing.
"We have a huge amount of extra capacity across Lothian with teams of vaccinators standing ready to ensure as many people as possible can get boosted by the Bells.
"We know people are really busy at this time of year, but we urge you to make time for it.
"If you haven't been boosted but could be, because it is 12 weeks since your second dose, please book an appointment now or go along to a drop-in clinic.
"If you have an appointment for January, you can drop in now and your later appointment will be cancelled for you.
"There are plenty of slots available and our centres are running very efficiently with very low queue times.
"Please don't delay. Every booster administered is a step on the road back to normality."
Dona Milne, Director of Public Health, NHS Lothian, said: "The Omicron variant is much more transmissible than previous strains.
"This means that although a smaller percentage of infected people may require hospitalisation, it is a smaller percentage of a far greater number of people, so still a lot of people.
"So, even if the admission rate is a third of what we have seen with previous strains, it is expected that the scale of Omicron could still be higher than we have seen before.
"I would ask everyone celebrating the new year to do so whilst following the public health guidance and be responsible as they enjoy the festivities.
"Please prioritise getting your vaccine and do not mix with more than three households and undertake a Lateral Flow Test before you mix with people.
"By taking these small steps, you can help stop the spread of Omicron."
