First Minister Mark Drakeford said the Welsh Government is doing "everything we can to accelerate our vaccination programme" as the Prime Minister warns of a "tidal wave of Omicron."
Drakeford said a booster vaccination was "vital" to our response to "a fast-moving form of coronavirus, which has the potential to cause a large wave of infections in Wales."
He continued: "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."
He was responding to a pre-recorded address to the nation on Sunday evening from Boris Johnson.
Johnson said Britain "must urgently reinforce our wall of vaccine protection" and he set a new deadline of jabbing everyone over 18 by the new year.
He said scientists had discovered that being fully vaccinated is "simply not enough" to prevent the spread of the coronavirus mutation and that, without a lightning speed mass booster campaign, the NHS could be overwhelmed.
The announcement comes as the UK Covid alert level was raised to Level 4, up from Level 3, following a rapid increase in the number of Omicron cases being recorded.
The recommendation was made to ministers by the country's four chief medical officers and NHS England's national medical director following advice from the UK Health Security Agency (UKHSA).
The First Minister said: “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.”