A leading scientist has warned that 'a big number' of people could be hospitalised with coronavirus as the Indian variant continues to rip through the UK.
Dr Adam Kucharski, an epidemiologist at the London School of Hygiene and Tropical Medicine, said it was "hard to justify easing restrictions on June 21, as initially set out by the government.
A member of the Scientific Pandemic Influenza Group on Modelling (Spi-M) Government advisory panel, Dr Adam told BBC Radio 4's Today programme there were a "number of concerning signs" following early evidence that first dose vaccines are not as effective against the so-called Delta variant and that the strain may increase the risk of being hospitalised from coronavirus.
He added: "I think it is particularly this increase in transmission that is potentially going to cause us considerable problems.
"We are getting estimates now firming up that we are looking at something potentially 40-60% more transmissible than the B.117, the Kent variant that was dominant."
"And that means that infections are going to really come at us quite fast and we are seeing that in the cases now, and we saw that in the ONS data yesterday."
Dr Kurcharski said the current picture meant that it was "hard to be confident" that a "big number" of people will not end up in hospital due to the spread of the Indian variant and the number of adults still unvaccinated in the UK.
He said Britain faces a different battle in the face of the dominance of the Indian variant, meaning it could be "hard to justify" easing further restrictions this month.
Asked whether the June 21 target for unlocking made him "nervous", the Government adviser said: "I think we have to accept the equation has changed here - we are not facing the virus that we were facing two months ago.
"If we were facing the B.117 (Kent) variant as the dominant one, the fact it (the vaccines) is working very well, case numbers are coming down nicely, we could have some more confidence that there could be reopening without seeing those surges.
"But we're not. Everyone is tired of this pandemic, they want this transition back to normality and that will happen, the effectiveness of two doses of the vaccine will eventually get us there.
"But if say in two weeks we're in a situation where hospitalisations have been rising, where local health systems are coming under pressure, I think it will be quite difficult to justify adding more transmission to that kind of situation."
Dr Kucharski described the current graph of infections as "U-shaped", with the vaccines having worked to quell infections from the Kent variant, but the Indian variant is now causing a fresh rise in cases.
But Chris Hopson, chief executive of NHS Providers said the number of people in hospital with the coronavirus variant first identified in India is increasing, but not significantly.
He told BBC Breakfast on Saturday the number of people in hospital in Bolton with Covid-19 peaked at 50, compared to 170 in November and 115 in January and February.
Mr Hopson said: "Infection rates have been increasing in a number of different places.
"We know that the hospitalisations are increasing, the rates of people coming into hospital in those areas are rising. But they are not rising very significantly."
He added: "Areas that were at the front of this wave, areas like Bolton, what's particularly interesting is that they have now got to the point where their community infections have started to decline."
But he did warn that those most recently in hospital in Bolton with Covid-19 were "a lot younger" than in previous waves of the pandemic.
Mr Hopson added: "The people who came in this round this time round were actually a lot younger and were a lot less at risk of very serious complication, less at risk of death, and what that means is that they were less demand on critical care.
"What we think we can start to say now, based on that experience, is that it does look as though the vaccines have broken the chain between catching Covid-19 and potentially being very, very seriously ill and potentially dying.
"There were very, very few people who have had those double jabs and had been able to have that build-up of protection after those jabs."
