THE health board is planning to administer more than 200,000 additional Covid-19 vaccinations over a period of 18 days.
Betsi Cadwaladr University Health Board (BCUHB) say they already have 60,000 booked appointments in place for North Wales residents during December.
They added that the logistics involved in more than tripling their current vaccination rate are "extremely challenging", but are "confident" they can make booster jabs available to all eligible adults by December 31.
A spokesperson from BCUHB said: "We are working incredibly hard behind the scenes to make this happen - but we need time to put the necessary building blocks in place.
"Over the next week, hundreds of additional staff and volunteers will join our vaccination effort. This will enable capacity at our existing vaccination clinics to increase and for them to open later. Additional clinics will also be introduced (including drop ins) and many more GP Practices and community pharmacies will begin delivering boosters."
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Ffion Johnstone, West Area Director, said: "We are having to find an additional 230,000 appointments for those who are eligible but don’t yet have an appointment this month.
"It is therefore critical that if you have a booked appointment in December you keep to it. Don't contact us to rearrange as this slows down our efforts to protect others. You will be waiting until January for an alternative.
"If you are housebound there is no need to contact us. We already have your details and are working as quickly as we can to get to you before the end of December."
Any eligible adult not yet invited to an appointment in December, can book online. Visit https://bcuhb.nhs.wales/covid-19/covid-19-vaccinations/covid-19-booster-programme-online-booking
Ms Johnstone added: "Appointments are being released in batches, to ensure that our IT infrastructure is able to manage demand.
"If you have received an appointment from 1st January onwards, you will be contacted via text with instructions on how to bring your appointment forward using our online booking service.
"Over the coming days we’ll be making 230,000 appointments available online at a range of clinics running across North Wales up until December 31.
"Booking online helps guarantee that you will receive your jab and reduces the time you have to queue. It also helps ensure that we have the correct levels of staff and vaccine available at each clinic."
Some people may be invited directly by their GP practice or community pharmacy for a booster but patients are urged not to phone up to enquire about appointments at this time. For further information, visit https://bcuhb.nhs.wales/covid-19/covid-19-vaccinations/vaccination-updates
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