The UK has reported its highest daily total of new coronavirus infections in a month - as it was revealed that cases of the “Indian variant” have nearly trebled in a week.
A further 2,874 lab-confirmed cases were confirmed on Thursday, the highest daily figure for new infections since April 19.
It brings the country’s total to 4,455,221 since the pandemic started early last year.
The overall incidence of infections remains low, while the number of people in hospital with Covid-19 fell below 900 for the first time since September.
But clusters of the B.1.617.2 variant, believed to be more transmissible than the dominant Kent variant, are growing quickly - and could derail Prime Minister Boris Johnson’s plans to fully reopen the economy on June 21.
Watch: COVID-19 - 'Clusters' across the country as number of Indian variant cases rises to 3,424
UK cases of the variant first found in India have risen to 3,424, up by 2,111 compared to figures released last week, Public Health England said.
It also represents a steep rise compared to figures given on Wednesday, when Health Minister Matt Hancock said there had been 2,967 cases of the variant.
“PHE will continue to monitor all variants closely, paying particular attention to the impact on hospitalisations and deaths which will help us to understand the protective effects of the vaccine,” said Meera Chand, Covid-19 Incident Director at PHE.
A further seven people have died within 28 days of testing positive for Covid-19 as of Thursday, bringing the UK total to 127,701.
Separate figures published by the UK’s statistics agencies show there have been 152,000 deaths registered in the UK where Covid was mentioned on the death certificate.
Government data up to May 19 shows that of the 58,489,834 jabs given in the UK so far, some 37,250,363 were first doses – a rise of 264,858 on the previous day.
Some 21,239,471 were second doses, an increase of 369,018.It comes as an infectious disease expert warned on Thursday that the UK could be at the start of a third wave of the virus.
Professor Andrew Hayward, from University College London, said he was “very concerned” about the Indian variant due to its super spreading abilities.
Asked on BBC Breakfast if the country was at the start of the third wave, he said: “I think so.”
Prof Hayward said that the UK should not “waste the opportunity” offered by vaccination by allowing people to travel widely.
“I think what we can see is that this strain can circulate very effectively,” the professor, who is a member of the Scientific Advisory Group for Emergencies, said.
“Although it was originally imported through travel to India, it’s spread fairly effectively, first of all within households and now more broadly within communities.
“So I don’t really see why it wouldn’t continue to spread in other parts of the country.”
Number 10 has said it was “still too early” to determine whether the Indian variant could delay lifting of all Covid restrictions on June 21.
Professor Jonathan Van-Tam told a Downing Street press conference: “I pitch this personally as a straight race between the transmissibility of this new variant … and vaccine delivery.”
That vaccine effort was given an important boost on Thursday as Public Health England revealed a real-world study has found the effectiveness of the AstraZeneca vaccine against Covid-19 increases to around 80-90 per cent after a second dose.
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