Brits were today urged to wear masks in crowded, enclosed places amid fears Covid hospital cases will hit an 18-month high.
Dame Dr Jenny Harries, one of the UK’s most senior health officials, warned a current wave of the virus has not yet peaked.
And she said it is “quite likely” hospitalisations will rise higher than the last wave this Spring.
In that wave of the Omicron BA.2 variant, the number of Covid patients in UK hospitals peaked at just over 20,000 at the start of April.
At the time, that was the highest number of Covid patients in UK hospitals since February 2021 - with admissions peaking at over 2,500 a day.
Hospital numbers fell between April and June but are now creeping up again, as Dame Jenny warned the BA.4 and BA.5 Omicron variants are “pushing and driving” a new wave.
The UK Health Security Agency chief executive told the BBC ’s Sunday Morning show: “It doesn't look as though that wave has finished yet.
“So we would anticipate that hospital cases will rise and it's possible, quite likely that they will actually peak over the previous BA.2 wave [in March 2022].
“But I think the overall impact we won't know. It's easy to say in retrospect - it's not so easy to model forward.”
Some 2.3 million people in private households are estimated to have had the virus last week, up 32% from a week earlier, according to the Office for National Statistics (ONS).
So far, this is well below the record 4.9million people who had Covid in one week during the Omicron BA.2 wave at the end of March.
But the number of people in UK hospitals with Covid has already risen from around 5,000 to more than 10,000 by June 27.
Dame Jenny told the BBC: “I think the the advice is still the same. We want people to take sensible precautionary advice.
“So routine things like washing your hands, keeping your distance, wearing a face covering if you're going into enclosed, poorly ventilated spaces.
“But we're still encouraging people to go about their normal lives but in that precautionary way.”
Despite not changing the advice - which says face masks are voluntary but "can help reduce the chance of you spreading infection to others, especially in crowded and enclosed spaces" - Dame Jenny suggested she has been wearing a mask more often due to the raised risk.
She said: “So I haven't been routinely wearing one but I do routinely carry one in my handbag wherever I go.
“Actually I have worn it in the last week for the very reason that I'm doing exactly what I've said, I'm adapting to the changing prevalence of infection.
“If I was symptomatic and had to go out, I would definitely wear one - clearly I would avoid doing that at all cost. In fact, if I got any respiratory infection it’s a good thing to do and I think it’s a new lesson for the country.”
Asked if it matters that a lot of people are getting infected with Covid, she said that aside from the effect on individuals, it also "matters on a national basis".
"Whilst we have an armament now of vaccines and antiviral treatments, we do have, as you've just highlighted, a rise in hospital admissions and occupancy," she said.
"And that means it's not just Covid that we're concerned about, but it's actually our ability to treat other illnesses as well."
Dame Jenny appealed to the "nearly 20% of the 75-plus year-old group" who have not had their spring booster to come forward.
