Austria will go back into a full Covid lockdown from Monday, the government has announced - with Germany believed to be on the brink of following suit.
It will become the first country in western Europe to reintroduce measures, with non-essential shops set to close and Austrians ordered to work from home.
People will be legally required to be double jabbed by February 1, Chancellor Alexander Schallenberg told a televised news conference today.
The restrictions will be in force until December, but will be reassessed after 10 days, authorities said.
Meanwhile authorities have sounded the alarm bells in Germany, where the infection rate is only slightly below that of the UK.
German health minister Jens Spahn, responding to Austria's announcement, said his country is gripped in a "national emergency", with rising cases sparking alarm.
Around two-thirds of Austria's population is fully vaccinated against coronavirus, one of the lowest rates in western Europe.
Its infections are among the highest on the continent, with a seven-day incidence of 991 per 100,000 people.
The UK currently has a rate of 580.74, while Germany's is 535.65, according to Our Wold In Data.
Announcing the measures, the Austrian Chancellor said: "We have not succeeded in convincing enough people to get vaccinated.
"It hurts that such measures still have to be taken."
Asked if Germany could rule out an Austrian-style full lockdown, Mr Spahn said: "We are now in a situation - even if this produces a news alert - where we can't rule anything out.
"We are in a national emergency."
Several governments have started to reimpose restrictions, ranging from Austria's full lockdown, to a partial lockdown in the Netherlands, to restrictions on the unvaccinated in parts of Germany, the Czech Republic and Slovakia.
Hungary will meanwhile make booster shots mandatory for all healthcare workers and require mask wearing in most indoor places from Saturday.
It comes amid warnings that the UK's health system is under immense strain heading into winter.
Today Professor John Edmunds, a member of the Scientific Advisory Group for Emergencies (Sage), told BBC Radio 4's the World at One programme: "I think there's a risk because of waning immunity in older individuals, and that's all adults, not just the elderly, that cases could really take off.
"So, I think it's really important that we boost immunity in older individuals and then we might be able to avoid any significant fourth wave."
He said the UK is ahead of other parts of Europe - where the Covid-19 situation is worsening - due to the rollout of boosters and the level of infection, but warned over the length of pressure being heaped on the NHS.
"It has been (under strain) for months and months, and that's not going to ease up any time soon because this very high level of infection that we have now and we've had for months isn't going to decline significantly," he added.
"We're going to have high levels of infection for many months, so I think the NHS will unfortunately be under significant strain - it may not get to breaking point, where we were close to before - but significant strain for a very long period of time is certainly on the cards."
