At least four people have died from the Indian variant of concern amid warnings a widespread relaxation of COVID rules on 21 June is "in doubt".
The new data, released by Public Health England (PHE), highlights growing concerns about the new variant with the government set to launch 'vaccination surges' in the worst-hit areas.
Boris Johnson has admitted the government is "anxious" about the growth of cases of the variant in the UK, which rose from 520 to 1,313 this week.
As well as a reported plan of flooding hotspots with COVID jabs for all over-18s, additional measures being taken to combat the spread include surge testing in certain areas and the deployment of a vaccine bus to encourage uptake among those who are eligible.
'June 21 plans in doubt'
The government's vaccine minister Nadhim Zahawi said on Friday morning there is currently no evidence the Indian variant "escapes the vaccines" or that it is more severe in its impact on people.
He said younger people in areas where there is a surge of the variant could be vaccinated sooner, adding: "The clinicians will look at all of this to see how we can flex the vaccination programme to make it as effective as possible to deal with this surge in this variant, the B1.617.2.
"They will make those decisions and we will be ready to implement, whether it’s vaccinating younger cohorts.
"We have been doing some work on multi-generational households where we vaccinate the whole household, over-18s, and of course the older groups who are already eligible.
"Or, bringing forward the second dose – we look at all of that and be guided by the clinicians as to what we do on that."
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Paul Hunter, professor in medicine at the University of East Anglia, said the 21 June lockdown lifting in England is in doubt, particularly if the Indian variant causes increases in cases in elderly people and a rise in people needing hospital care.
He told BBC Radio 4’s Today programme: "At the moment the hospitalisation rate doesn’t seem to be increasing, although if this becomes much more common we’ll almost certainly see some increase, so I think it’s certainly a concern.
"I think the step four is in doubt in June now, but we really need to see what impact it has on severe disease before we can really be certain."
Asked why 21 June is in doubt, he said: "If the Indian variant of the epidemic continues to increase at the same rate as it has over recent weeks, we’re going to have a huge number of cases by June.
"The issue though is that because it seems to be spreading in unvaccinated younger people at the moment and not yet that much more active in older people maybe we’ll be able to weather it and we’ll still be able to have the step four in June.
"But if that increases cases in elderly and starts to increase hospitalisations, and puts pressure on the NHS again then I think step four would be in doubt."
In a meeting on 5 May, the Scientific Advisory Group for Emergencies (Sage) released its own warning about the rise of the variant in England, saying: “There has been a significant recent increase in prevalence of the B.1.617.2 [Indian] variant, including some community transmission.
“PHE is currently prioritising case finding and containment for this variant. Early indications, including from international experience, are that this variant may be more transmissible than the B.1.1.7 [Kent] variant.”
In the same report, Sage concluded there was not enough data to say whether the variant was more deadly.
NHS leaders have also urged the government to ensure they are being led by the data, even if prolonging some measures beyond 21 June proves unpopular.
The NHS Confederation's chief executive, Danny Mortimer, said: “With growing concern around the spread of the Indian variant of COVID, the government must be guided by the data.
“If there is any indication that the spread is no longer sufficiently under control, it must be prepared to adjust the timetable for easing lockdown, however unpopular that decision may be."
Wales holds back
In Wales, which is set to move to alert level two on Monday with the reopening of indoor hospitality and entertainment venues, first minister Mark Drakeford said officials had "decided to hold back" on relaxing some restrictions due to concerns about the Indian variant.
Asked if the variant gave him any pause for thought, told BBC Radio 4’s Today Programme: "Yes, it certainly does. There were 17 cases of the Indian variant in Wales yesterday and over 700 in England.
"And as we were just hearing, there’s quite a concentration of that in the north-west of England and there’s a lot of traffic between the north-east of Wales and the north-west of England so we were considering a small number of further easements from Monday but have decided to hold back on those until we get the advice from Sage (Scientific Advisory Group for Emergencies) met yesterday, our own scientific advice which we’ll receive imminently, just to make sure that we are continuing to take a precautionary approach in case the Indian variant is on the march, and therefore Wales would be vulnerable to it as well."
Asked if he would be prepared to delay further steps in his road map if advice from Sage suggested it was necessary, Drakeford said: "Yes, we would. We tried our best to follow the scientific advice at every step and if the advice were to be that we should hold back on some further easements because the risks in doing so would be too great then certainly that is what we would do."
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