Britain's health secretary has refused to rule out imposing tougher COVID-19 restrictions before Christmas amid the rapid rise of infections and continuing uncertainty about the omicron variant.
Health Secretary Sajid Javid said that the government was assessing the fast-moving situation and urged the public to be cautious as scientists examine the data.
Much is still unknown about the highly transmissible new variant, even as hospitals brace for a surge in infections, he told the BBC.
"There are no guarantees in this pandemic, I don't think," Mr Javid replied when asked about the potential for new restrictions.
"At this point, we just have to keep everything under review."
Prime Minister Boris Johnson last week reinstated rules requiring face masks in shops and ordered people to show proof of vaccination or a negative coronavirus test before entering nightclubs and other crowded venues.
He has championed a program that relies on vaccines, an operation that delivered 830,000 booster shots on Saturday alone.
Vaccination sites are being asked to operate 12 hours a day, seven days a week with shopping centres, cathedrals and soccer stadiums into mass vaccination centres.
Some sites are working 24 hours a day to make it easier for people who work shifts.
But the government's scientific advisers believe it won't be enough and have recommended more far-reaching restrictions to prevent UK. hospitals from being overwhelmed, according to leaked minutes from a meeting of the Scientific Advisory Group for Emergencies seen by the BBC.
"We can't wait for hospitalisations to go through the roof before we do something about it, because by then it's too late,″ Professor David Spiegelhalter told Sky News.
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The British Medical Association is warning that almost 50,000 doctors, nurses and other National Health Service staff in England could be off sick with COVID-19 by Christmas Day unless additional measures are introduced.
Mr Johnson's Conservative government needs further measures beyond just trying to vaccine-boost its way out of the situation, said Chaand Nagpaul, chair of the association's council.
The UK government on Sunday reported 82,886 more lab-confirmed COVID-19 cases in a day.
With over 147,000 deaths, Britain already has Europe's highest COVID-19 death toll after Russia.