LONDON (Reuters) – Britain is ramping up its mass rollout of COVID-19 vaccinations as its top medical officer said the next few weeks of the pandemic will be the worst yet, with deaths and cases hitting record highs, putting the health service under huge pressure.

Deaths from the virus have now exceeded 81,000 in the United Kingdom with more than 3 million people testing positive, and a new variant of the disease is surging through the population, with one in 20 people in parts of London now infected.

“The next few weeks are going to be the worst weeks of this pandemic in terms of numbers into the NHS (National Health Service),” Chris Whitty, the British government’s chief medical adviser said.

“Anybody who is not shocked by the number of people in hospital who are seriously ill at the moment and who are dying over the course of this pandemic, I think, has not understood this at all. This is an appalling situation,” he told BBC TV.

In a bid to get on top of the pandemic and to try to restore some degree of normality by the spring, Britain is planning the country’s largest ever vaccination programme, shots initially offered to all those in its top four priority categories – about 15 million people – by the middle of next month.

Having become the first country to approve vaccines developed by Pfizer-BioNTech and by Oxford-AstraZeneca, Britain will open seven large-scale vaccination centres as it seeks to reach a target of offering shots to 15 million people by the middle of next month.

“The vaccinations are really beginning to ramp up, 200,000 a day, we’ve done an incredible job this past week,” vaccine minister Nadhim Zahawi told Sky News, saying they would offer shots to those in the highest risk levels, the eldest and frontline health workers, by February 15.

More than 81,400 people in the United Kingdom have died within 28 days of receiving a positive COVID-19 test, the fifth-highest official death toll globally.

On Friday, London’s Mayor warned the British capital’s hospitals were in danger of being overwhelmed by COVID patients, and ministers and health chiefs have pleaded with people to respect lockdown measures and stay at home unless it was essential to go out.

“We have got to be able to maintain this for several more weeks now,” said Whitty, adding it would require “significant action” until sometime in the spring.

“We are now very close to the point, with the vaccinations, where we are able to get on top of this, but it is not yet.”

There have been calls for the government to take tougher action against those who break the rules, such as refusing to wear masks in supermarkets, amid concern the disease is being spread by shoppers in the stores.

“These rules are not boundaries to be pushed against. These rules are there to try and make sure we bring this virus under control,” Zahawi said.