This brings an end to our live coverage of the Welsh government's coronavirus briefing.

What we learned:

• There are no cases of the Omicron variant in Wales so far
• Isolation rules are being tightened for anyone who comes into close contact of a positive Omicron case
• Travel rules are being tightened for all international arrivals
• Speeding up the roll out of the booster programme will be "a challenge"
• People mixing indoors poses a threat over Christmas

To keep updated with the latest news on the coronavirus situation in Wales, read our main story.

Covid booster jabs will be offered to all over-18s in the UK to help stop a potential wave of infections driven by the new variant Omicron.

The Joint Committee on Vaccination and Immunisation made a series of recommendations to expand the booster rollout.

It included reducing the minimum gap between the second vaccine dose and booster from six to three months.

Children aged 12-15 should also be invited for a second jab.

Image source, Getty Images

Secondary school pupils are being urged to wear face masks in classes following the emergence of the Omicron variant.

The move goes further than advice given in England to wear face masks in communal areas, and brings Wales level with Scotland and Northern Ireland.

Image source, Getty Images

The boss of Moderna has cast doubts on the effectiveness of vaccines against the new Omicron variant.

Stephane Bancel told the Financial Times , externalhe thought there would be a "material drop" in vaccine efficacy.

The Covid variant was first detected in South Africa and symptoms have been mild so far.

But travel restrictions have been imposed as a precaution by places including the UK, the EU and the US.

Mr Bancel predicted existing vaccines would be less effective in staving off Omicron, and that it would take months for drugs companies to update vaccines.

Pfizer-Biontech previously said it would be able to roll out an updated version of its vaccine "within 100 days".

Health minister Eluned Morgan said there can be “no exceptions” to the self-isolation rules with regards to the Cardiff Rugby squad who are in red list country South Africa.

It follows two positive cases in the squad, one of them suspected to be the Omicron variant.

“We are very interested in bringing our boys home but they will have to come home in the same way as everybody else.

“There will be no exceptions. There will be a need for them to self-isolate but there are no places in Wales for them to self-isolate."

On isolation in Welsh hotels, she added: “We thought it would increase the health risk if we were to transport someone from an airport into a hotel in Wales.”

She said it would be “too big an ask” to expect a Welsh hotel to become a self-isolation hotel in the run up to the “busy Christmas period”.

Speaking about the introduction of more measures in secondary schools and colleges, Mary van den Heuvel, senior policy officer for National Education Union Cymru, said the union have "long been calling for more mitigations".

She added: "In light of the new variant, it is important we act quickly – and measures such as masks in classrooms will be welcome.

“Scientists will learn more about Omicron in the coming days but taking action in schools and colleges now will help support learners and the education workforce in the run up to Christmas.

"We only have three weeks left of the school term, and it is important that every possible measure is put in place now."

The Welsh Conservatives want a dedicated vaccines ministers as part of plans to deal with the Omicron variant.

Other measures the party has called for include rapidly rolling out booster walk-in centres and reopening mass vaccination centres, which have now closed.

The party also wants to see vaccine passports scrapped if Omicron proves no more dangerous than the Delta variant.

Health spokesman Russell George said: “The health minister is doing her best in difficult circumstances but given the pressures facing public health in Wales and the importance of the vaccine roll out, it’s clear the first minister needs to provide support in the form of a dedicated vaccines minister moving forward."

The Welsh government wants to keep schools open "as long as possible", despite concerns about the new variant, Eluned Morgan added.

In terms of educational and mental health issues if schools are closed, she said: "We are very aware of the damage that this can do to children, to pull them out of school causes difficulties.

"So we will do our utmost to try and keep the schools open, which is why we've introduced these measures of face coverings, not just in corridors but also in classrooms.

"We would like children to undertake tests next year, for every day they miss off school it's more difficult for us to continue with those tests.

"So that will be a call for the education minister, and I know he's keeping a very close eye on the situation."

The new Covid-19 variant Omicron was detected in the Europe earlier than previously thought.

Dutch health officials said it was present in the Netherlands more than a week ago and was found in two newly sequenced test samples taken between 19 November and 23 November.

We first heard about the variant when it was first detected in South Africa on 24 November.

"It is not clear yet whether these people have visited southern Africa," an official said.

Image source, Getty Images

It is "too early to say yet" what the Covid situation is likely to be as we enter the Christmas period, the health minister says.

She told journalists she would "urge people to act with caution over the Christmas period and to take very seriously the situation and the threat, indeed, of mixing with other people indoors during this time".

"It is something that we need to take seriously. Omicron has not yet arrived in Wales, but it is simply a question of time before it does."

A health board said phone calls started flooding in after the announcement about speeding up the booster-jab programme.

Cwm Taf Morgannwg university health board said it received hundreds of calls from people asking about jabs for all over-18s as a result of "media stories" on Monday.

The calls were stopping other patients getting through to arrange appointments, it said on Facebook.

“We politely ask you do not call us about this,” its message said.

After Monday's announcement by the UK's Joint Committee on Vaccination and Immunisation, Hywel Dda health board said its vaccination team was “urgently working through what this announcement means for our delivery of Covid-19 vaccines across our seven vaccination centres”.

People have been asked only to call to arrange a booster if they were over 40 or in an at-risk group and it had been 28 weeks or more since their second dose.

Meanwhile, on Tuesday morning, Cardiff and Vale health board posted a message to say its vaccination booking line was down.

“We are working to resolve the issue as soon as possible, but apologies for an inconvenience caused in the meantime,” it said.

The health minister said self-isolation rules were being changed so everyone identified as a close contact of a confirmed or probable Omicron case in Wales will need to isolate for 10 days “regardless of their vaccination status or age”.

Currently, vaccinated people only have to isolate if a close contact in their household tests positive for coronavirus, while they get the result of a PCR test.

Image source, Getty

Expanding the vaccination programme will be challenging, Dr Richardson says.

“It will mean increasing the speed of the roll out and increasing the workforce to ensure we can offer boosters and second vaccines to everyone who is eligible,” she added.

“We have the supply of the vaccine and we are working with the NHS to put plans in place this week.

“We’re looking at creating more clinics, at using drive-through models, we’ll be working with primary care colleagues wherever we can and with other public service staff who are trained vaccinators to make sure we can protect as many people as possible.”

Dr Gill Richardson says more than 840,000 people have had booster jabs in Wales, with the majority of those being people aged 65 and over, those living and working in care homes and frontline NHS workers.

Image source, Getty Images

Eluned Morgan confirms anyone returning to the UK will have to take a PCR test by day two after returning home, regardless of vaccination status.

Those arriving from one of the 10 countries on the red list will have to stay in a managed quarantine hotel, without exception.

Eluned Morgan has started the briefing.

“This is another serious development in the pandemic and one we are taking seriously. There is still a lot we don’t know about this variant," she says.

"We won’t know the answers until more research has been done. The European Centre for Disease Prevention and Control has warned this is the most divergent variant so far.”

But she said there are no cases in Wales at the moment.