Public Health England on Friday said that early evidence suggested the levels of coronavirus found in people infected with the Delta variant are similar whether or not they are vaccinated, with possible implications for their infectiousness.

“Some initial findings… indicate that levels of virus in those who become infected with Delta having already been vaccinated may be similar to levels found in unvaccinated people,” Public Health England said in a statement.

“This may have implications for people’s infectiousness, whether they have been vaccinated or not. However, this is early exploratory analysis and further targeted studies are needed to confirm whether this is the case.”

if the findings are confirmed, it could have” huge implications for transmissibility” as “data has consistently shown the vaccine slows down and should, effectively, stop the spread of the virus”.

Dr Simon Clarke, a microbiology professor at Reading University, told Sky News the early findings were a “big deal”.

He said: “If the vaccine only blocks transmission by, say, 50% you’ll never get herd immunity even with a 100% vaccine uptake.”

The Delta variant, which originated in India, remains dominant in the UK and accounts for approximately 99% of cases, said PHE in its latest variant briefing.

Latest hospitalisation data confirm again that vaccines, while providing high levels of protection, are not 100% effective.

Of recent admissions for the virus, 808 (55.1%) were unvaccinated, while 512 (34.9%) had received both doses of a vaccine, said PHE.

“We must also remember that the vaccines do not eliminate all risk: it is still possible to become unwell with COVID and infect others,” said Dr Jenny Harries, head of the UK Health Security Agency.

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