Data from the UK Health Security Agency (UKHSA), which takes into account levels of infection in the community as well as hospitals, shows infection rates are continuing to rise, but not as sharply as they were in the previous week.
But officials stressed it was too early to take that as a sign that flu could be peaking.
They said the virus was unpredictable and a lull could be followed by another surge.
Dr Conall Watson, an infectious diseases expert at the UKHSA, urged people who are eligible for a free flu vaccine on the NHS, which includes the over 65s, those with certain health conditions and pregnant women, to still come forward if they had not yet got one.
“There is still plenty of flu vaccine available to protect those who need it – what’s running out is time to be protected ahead of Christmas.
“If you are eligible this is the last chance to get protected as we head into Christmas – so make an appointment with the NHS today.”
It can take up to two weeks following vaccination to develop the fullest protection from the jab, Dr Watson added.
Dr Vicky Price, president of the Society for Acute Medicine, said winter viruses were placing further strain on an “already buckling system”.
She said patients were facing long waits in A&E as hospital staff were being overloaded with patients.
But she accused NHS England and the government of using it as a “convenient scapegoat” for the “predictable breakdown” in NHS capacity caused by workforce shortages.
“The situation in emergency departments has become so dire that what was once considered a critical incident is now seen as normal and routine. What is happening is not an isolated emergency, but the culmination of systemic failure.”