The country is "back in the eye of the storm", according to the head of the NHS, with the number of patients being treated for COVID-19 in England's hospitals overtaking the peak back in April.
Figures from NHS England have revealed there were 20,426 patients being treated in hospitals as of 8am on Monday, compared with the 18,974 patients recorded on 12 April.
On Tuesday, the UK recorded its highest daily increase in coronavirus cases since the pandemic began with 53,135 positive tests.
During a visit to an NHS vaccination centre, the chief executive of the NHS, Sir Simon Stevens, praised staff but said: "Now again we are back in the eye of the storm with a second wave of coronavirus sweeping Europe and, indeed, this country.
"Many of us have lost family, friends, colleagues and - at a time of year when we would normally be celebrating - a lot of people are understandably feeling anxious, frustrated and tired."
But sounding a note of hope, Sir Simon added: "We think that by late spring with vaccine supplies continuing to come on stream we will have been able to offer all vulnerable people across this country COVID vaccination.
"That perhaps provides the biggest chink of hope for the year ahead."
His comments come on the day that the patients who received the first vaccinations three weeks ago will receive their booster jab.
They also come as the pressure continues to grow on the NHS at a time of year that is already difficult.
Dr Samantha Batt-Rawden, president of the Doctors' Association UK, said in a widely shared Twitter thread that she and her colleagues are "at breaking point".
The senior intensive care registrar wrote: "Today we learnt that we have more patients with COVID in hospital than ever before in England. This is not a drill. Please believe us.
"We are incredibly thin on the ground. NHS staff have not been prioritised for the vaccine and are going off sick in droves with the new strain.
"Trusts are so desperate they are tweeting out for medical students to help in ICU. This was confirmed by a consultant on the ground.
"When staff have spoken up on Twitter they have been told this is all a hoax. It's not.
"Try holding an iPad for a patient to say goodbye to their family. Or having to ventilate a colleague. This is real and happening right now. Staff are broken and need support now more than ever."
Lewisham and Greenwich NHS Trust revealed that an internal incident was declared at Queen Elizabeth Hospital in southeast London on Sunday "as a precautionary step due to the high number of COVID-positive patients we are seeing at the hospital".
The trust added that all patients received the treatment they needed and the situation is being monitored.
And the capital's ambulance service described Boxing Day as one of its busiest days ever.
Consultant emergency physician Adrian Boyle told Sky News: "You feel terrible and a sense of helplessness when you can't offload an ambulance because your emergency department is full.
"It creates this sense you are failing your patients just because there's a sheer lack of space to look after people."
The medical director of Public Health England, Dr Yvonne Doyle, said the "very high level of infection is of growing concern at a time when our hospitals are at their most vulnerable".
"We have all made huge sacrifices this year but we must all continue to play our part in stopping the spread of the virus which is still replicating fast."