The reopening of schools to all pupils could lead to an increase in new coronavirus cases before the further easing of restrictions.

Boris Johnson has ruled out suggestions that the Government should accelerate its planned lifting of lockdown guidelines as the reopening of schools is likely to cause a brief rise in infections.

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Tens of thousands of pupils in Norfolk this week put on their uniforms and returned to lessons this week for the first time in two months.

Despite more than 20 million people now vaccinated in the UK, the prime minister said a "risk of increased transmission is inevitable" following the return of pupils.

Norwich Evening News: Children return to school for the first time in two months as part of the first stage of lockdown easing.Children return to school for the first time in two months as part of the first stage of lockdown easing. (Image: PA)

Flegg High School and Toftwood Infant School in Dereham were among the schools that confirmed Covid cases in the first two days of pupils being back.

Paul Hunter, professor of medicine at University of East Anglia's Norwich Medical School, said although risks of returning to schools for individual children and teachers was low, school transmission was likely to push up general infection rates again.

It comes as Professor Chris Whitty, England's chief medical officer, told MPs the situation could still "turn bad" with another summer surge despite the vaccination programme.

All eyes will now be on the effect school openings have on the Covid R rate, before the Government’s ‘roadmap’ for coming out of lockdown sees households allowed to mix from March 29 and shops reopening on April 12.

Norwich Evening News: Paul Hunter, professor of medicine at the UEA, believes it is the right time for increased social interaction between households amid the coronavirus pandemic. Picture: ArchantPaul Hunter, professor of medicine at the UEA, believes it is the right time for increased social interaction between households amid the coronavirus pandemic. Picture: Archant (Image: Archant © 2013)

Dr Hunter said: "Case numbers could, in theory, go up again if we release too quickly but, reopening schools and then subsequently opening up society after that, it is a realistic expectation that by late spring we will almost certainly be under substantially less restrictions than we are at the moment."

Unions and school leaders have criticised the decision not to prioritise school staff in “crowded” classrooms in the next phase of the Covid-19 vaccine rollout.

Norwich Evening News: Social distancing signage on view as children return to school for the first time in two months as part of the first stage of lockdown easing.Social distancing signage on view as children return to school for the first time in two months as part of the first stage of lockdown easing. (Image: PA)

But new figures from the Schools Infection Survey, conducted at a small sample of schools in December by the Office for National Statistics, found school staff were not at a higher risk of being infected by coronavirus than other adults of working age.

Dr Shamez Ladhani, a consultant epidemiologist with Public Health England and the study’s chief investigator, said: “I think where we are now is in a really amazing place for reopening schools the right way.

Norwich Evening News: Erin Horn looking in a mirror while taking a Lateral Flow Test as pupils return to school for the first time in two months as part of the first stage of lockdown easing.Erin Horn looking in a mirror while taking a Lateral Flow Test as pupils return to school for the first time in two months as part of the first stage of lockdown easing. (Image: PA)

“The country is still in lockdown, the infection rates are falling very, very rapidly, community infection and transmissions are going to be very low when they go back to school.”