The Indian variant of Covid-19 is potentially 60 per cent more infectious than the strain first identified in the UK, a leading epidemiologist said on Friday.
Prof Neil Ferguson, who led the Covid-19 response team at Imperial College London, while discussing the Indian strain said: "The news is not as positive as I would like."
It is also known as the Delta variant after all Covid-19 mutations were renamed by the World Health Organisation this week.
"The best estimate at the moment is this variant may be 60 per cent more transmissible than the Alpha variant," Prof Ferguson told BBC Radio 4's Today programme.
“It partially escapes vaccine immunity, although there is still a good deal of protection, and may well cause severe disease from the hospitalisation data reported.
“It could be anywhere from 30 to 100 per cent more, but 60 per cent is a good central estimate.”
Public Health England said on Thursday that the strain was now the dominant variant in the UK, with 12,431 cases recorded up to June 2 – a sharp increase from the 6,959 infections reported in the previous week.
Health officials said there was evidence to suggest that people infected with the variant were at greater risk of being admitted to hospital.
However, about two out of three patients with the Indian strain had not been vaccinated against Covid-19.
Of the 479 people admitted to hospital in England between February 1 and May 31, all of whom had the Indian variant, 309 were unvaccinated. Eighteen had received two doses of a Covid-19 vaccine.
From 137 cases admitted to hospital overnight, 90 had not been inoculated, while seven had received two vaccine doses.
Prof Ferguson, a UK government adviser, said unvaccinated people faced a twofold risk of being admitted to hospital with Covid-19.
“It’s clear the vaccines are still having a substantial effect, though it may be slightly compromised,” he said
“We’re still waiting for data on how much this variant can evade immunity, which can protect you against hospitalisation.”
He said the Nepal variant, blamed in part for the UK's decision to remove Portugal from its green list for travel, was essentially the Indian variant with a further mutation.
Asked about the prospects of the UK lifting social distancing restrictions on June 21 as planned, Prof Ferguson said it was a “difficult judgment call” for British Prime Minister Boris Johnson.
“The data is pointing this week in a more negative direction than last week,” he said.