First Minister Mark Drakeford has warned of "further steps" to "keep Wales safe" in a statement after Boris Johnson said the UK faced an Omicron "tidal wave".
The Prime Minister issued a sombre warning in a TV broadcast as he made the ambitious pledge that booster jabs will be offered to everyone over 18 in England from this week.
The PM said: "No one should be in any doubt, there is a tidal wave of Omicron coming."
A statement was later released by Mr Drakeford - saying they were stepping up the booster programme in Wales and warned that the country was facing a "serious situation" and more measures could be introduced.
In the latest 21-day review no changes were made to the restrictions but they did move to weekly reviews from now on as concerns grow about how quickly the new variant could spread.
Wales has so far only reported a small number of Omicron cases and overall Covid numbers are stable but in Scotland they are already seeing a surge in infections.
The impact on hospitalisations is not yet known but Mr Johnson said "at this point our scientists cannot say that Omicron is less severe".
In Wales on December 9 the number of people in hospitals with confirmed or suspected Covid or is recovering from coronavirus is 554 - compared to 1,936 on the same date last year. However total inpatient numbers are higher (8,624) on that same date, compared to last year (7,968).
Mr Drakeford said: "We are learning more about the Omicron variant every day.
“This is a fast-moving form of coronavirus, which has the potential to cause a large wave of infections in Wales. This could lead to large numbers of people needing hospital treatment at a time when our NHS is under significant pressure.
“Our best defence continues to be vaccination. Emerging evidence shows the booster dose is vital.
“We are doing everything we can to accelerate our vaccination programme to increase the number of people who will receive their booster in the coming days and weeks. Older people and those at greatest risk are being prioritised at the moment.
“We are increasing the number of clinics and their opening hours; we have asked all available staff to join vaccination teams to support this national effort.
“Please make having your booster a priority. It will be one of the most important things you can do to protect yourself against coronavirus and this new variant.
“The Cabinet is closely monitoring this rapidly changing public health situation and has moved to a weekly review cycle.
“We are facing a very serious situation and we may need to take further steps to keep Wales safe. I will continue to keep Wales updated.”
