England’s chief medical officer has urged people not to delay getting their Covid-19 vaccine, saying there are some “very sick” young adults in hospital with the virus.

Professor Chris Whitty branded it “stark” that the majority of Covid patients have not had a jab.

He said he had spent four weeks working on a Covid ward and told how many “regret delaying” their vaccination.

His comments came as new figures showed that 55% people in hospital with the Delta variant – which is dominant in the UK – have not been jabbed.

The data from Public Health England (PHE) also shows that 74% of people under 50 in hospital with the variant had not been vaccinated.

Almost two thirds of people in the same age group who died in England with the Delta variant were not vaccinated against the virus, the figures show.

Prof Whitty tweeted: “The great majority of adults have been vaccinated.

“Four weeks working on a Covid ward makes stark the reality that the majority of our hospitalised Covid patients are unvaccinated and regret delaying. Some are very sick including young adults.

“Please don’t delay your vaccine.”

The UK’s vaccine programme has so far seen around three-quarters of adults in the UK double-jabbed.

But nearly three million young adults have not had a first dose, according to figures published earlier this week by the four health agencies.

There has been a concerted effort to get as many people vaccinated as possible, with 16 and 17-year-olds getting letters and text reminders this week inviting them for a jab.

The PHE data, published on Friday, showed there were 1,189 deaths up to August 15 of people who were either confirmed or likely to have had the Delta variant and who died within 28 days of a positive test.

While the majority of deaths with the variant were in people aged 50 or over, the under-50s account for more when it comes to hospital admissions.

Of the 1,076 deaths of people aged 50 or over, 318 (30%) were unvaccinated, 93 (9%) had received one dose of vaccine and 652 (61%) had received both.

Of the 113 deaths of people under 50, 72 (64%) were unvaccinated, 11 (10%) had received one jab and 27 (24%) had received both.

Of the 3,173 people aged 50 or over admitted to hospital in England up to the middle of this month who were either confirmed or likely to have had the Delta variant, 989 (31%) were not jabbed.

A total of 318 (10%) had received one dose of vaccine and 1,838 (58%) had received two.

Most of the 4,112 people aged under 50 had not had a jab, making up 3,044 (74%) of the total.

A total of 631 (15%) had received one dose of vaccine and 366 (9%) had received both doses.

Coronavirus infection levels remain high across the UK and have risen in Wales and Northern Ireland, according to the latest estimates from the Office for National Statistics (ONS).

They are highest in Northern Ireland, with an estimate of one in 50 people in private households having the virus in the week to August 14 – the highest level since the week to January 23.

The estimate is one in 80 people in England, one in 130 in Wales and one in 200 in Scotland.

The ONS said in England rates of infection have increased for people aged 35 to 49 but have fallen for those in school years seven to 11, for 25 to 34-year-olds and for people aged 70 and over.

The coronavirus reproduction number, or R value, in England has gone up and is between 0.9 and 1.2, according to the latest Government figures.

Last week the figure, which represents the average number of people each Covid-19 positive person goes on to infect, was between 0.8 to 1.

A further 114 people had died within 28 days of testing positive for Covid-19 as of Friday, while there had been a further 37,314 lab-confirmed cases in the UK, the Government said.

Meanwhile, the UK’s medicines regulator has approved use of a drug given to former US president Donald Trump when he was admitted to hospital with Covid-19 last year.

It is the first treatment set to be used in the UK using man-made antibodies designed specifically to prevent and fight coronavirus.

Health Secretary Sajid Javid hailed it as “fantastic news” and said he hoped it can be rolled out for patients on the NHS “as soon as possible”.

The Medicines and Healthcare products Regulatory Agency (MHRA) said the clinical trial data it had assessed has shown Ronapreve – previously known as REGN-Cov2 – can be used to prevent infection, treat symptoms of serious infection and reduce the likelihood of being admitted to hospital due to the virus.

Elsewhere, pharmaceutical giant AstraZeneca said a new coronavirus “antibody cocktail” treatment aimed at people who cannot be vaccinated can reduce the risk of developing symptomatic disease by 77%.

It is the first non-vaccine antibody combination modified to provide potentially long-lasting protection that has demonstrated prevention of Covid-19 in a clinical trial, the firm said.