Professor Stephen Powis said the health service was in a “precarious position” and urged people to stick to the rules until immunisations have had an effect. The medical director said: “It takes a week or two after the first vaccination to start to develop immunity against the virus, so we don’t expect that we will see an impact on the NHS until into February.”
The warning came as a further 599 deaths and 37,535 cases were recorded across the UK as infections continued to drop.
The daily case number was down a fifth on the previous Monday’s total, and down 36 per cent compared to two weeks ago.
Prof Powis added: “We know lockdown measures work, we saw that in April, we saw it in November.
“And we are beginning to see it now. That’s good news because we have also had this new strain which is more transmissible.
“So although infection rates are beginning to slow, it will be a number of weeks before we start to see that effect on the number of people in hospitals.”
Prof Powis said demand on hospitals rocketed since Christmas Eve.
He said: “We have seen 15,000 new people being admitted, that’s well over 20 hospitals’ worth of new patients.
“So it’s really important that everybody sticks to those social distancing guidelines.” He said the NHS relied on the public “sticking to the rules”.
He added: “That will reduce deaths and of course take pressure off hospitals.”
Prof Powis also urged those who have received the vaccine to continue following social-distancing measures.
He said: “It will stop you getting severe illness but we don’t yet know how good the vaccines are at stopping the transmission of the virus.”