LONDON, United Kingdom -- Britain's government on Wednesday rejected calls to trigger "Plan B" measures to limit spiralling COVID infection rates, even as it warned that cases could reach as many 100,000 a day over the winter months.

Healthcare leaders have urged the government to reinstate some restrictions to prevent the close-contact spread of the coronavirus, including the wearing of masks indoors, to ease pressure on hospitals.

But Health Secretary Sajid Javid played down concerns about the stubbornly high figures, which are nudging 50,000 new cases and 1,000 hospital admissions a day.

Javid said winter, during which health services are typically stretched with other seasonal viruses such as influenza, "will pose the greatest threat to our recovery".

"Cases are rising. They could go yet as high as 100,000 a day. This pandemic is not over," he told reporters.

"We are looking closely at the data but we won't be implementing our Plan B of contingency measures at this point.

"But we will be staying vigilant, preparing for all eventualities, while strengthening our vital defences that can help us fight back against the virus." Matthew Taylor, head of the NHS Confederation representing the state-run health service in England, Wales and Northern Ireland, said hospitals were feeling severe pressure and action was needed before the cold weather starts in earnest.

Worsening Covid-19 rates were affecting key targets in areas such as waits in emergency departments, ambulance response times and treatment backlogs, he said.

"Is it better to act early and take measures which don't stop the economy working -- but I recognise they are inconvenient for people -- or do we wait for things to get worse and possibly risk having to take more severe measures?" - Anti-viral deal - The government has faced repeated criticism for reacting too slowly at key stages of the pandemic since early last year. Britain's death toll exceeds 139,000, second only to Russia in Europe.

Ministers lifted coronavirus restrictions in July as vaccination rates increased, hoping to kick-start much-needed economic recovery.

The current rise in cases has been attributed to high numbers of infections in school-age children, who returned to the classroom after a disrupted year in September.

But ministers maintain the situation does not yet warrant a return to compulsory indoor mask-wearing and working from home where possible, among other restrictions.

Javid said the country was "learning to live with" Covid, and pointed to the mass vaccination programme for breaking the link between hospital admissions and deaths.

According to the latest figures Wednesday, 7,891 people were in hospital with Covid-19, including 850 on ventilation. A total of 179 had died within 28 days of a positive test.

The government is urging the over-50s and clinically vulnerable to take up the offer of a third booster vaccine to give further protection, as well as get flu jabs.

It has also signed a deal for 730,000 anti-viral drugs from pharma giants Pfizer and Merck which, subject to regulatory approval, will speed up recovery times and stop infections progressing, Javid said.

Britain's high infection rates -- currently the second highest in the world after the United States, according to Johns Hopkins University -- contrast sharply with its European neighbours.

That has prompted fresh scrutiny of the decision to relax all restrictions.

Britain began its vaccination programme in December last year, raising questions about whether immunity is now waning, similar to the experience in another fast-starter, Israel.

It has mainly used the Oxford-AstraZeneca vaccine, which was shown to be less effective at preventing infection from the Delta variant than the mRNA vaccines such as Pfizer-BioNTech and Moderna predominantly used in Europe.