There has been a “sharp increase” in the number of cases of Covid-19 among primary school pupils, but cases have dropped among secondary school students, new figures reveal.

The latest figures from the Office for National Statistics were highlighted during a briefing today on the coronavirus in schools from the Independent SAGE group

Christina Pagel, professor of operational research at UCL, also told the briefing that there was a potential for outbreaks in schools to be going unnoticed because of asymptomatic transmission.

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She warned that there had been a “relentless doubling” of Covid-19 deaths every two weeks but added that a circuit breaker lockdown held now could begin to start saving lives in December.

Prof Pagel presented a graph highlighting the number of cases in different age groups.

This showed that the proportion of pupils in Years 2 to 6 with Covid-19 increased from 9 October to 16 October.

It also showed that the proportion of 11- to 16-year-olds with Covid declined over the same period.

Prof Pagel said that there were currently 400,000 pupils self-isolating as a result of potential contact with a Covid case.

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She also highlighted that although attendance was, on average, 86 per cent in secondary schools, in some areas with high Covid transmission attendance was much lower. She said that in Knowsley it was 61 per cent and in Liverpool it was 67 per cent.

Prof Pagel said Independent SAGE was repeating its calls for a “circuit-breaker” lockdown and warned that the longer it was left before this was implemented, the longer the lockdown might need to be.

She presented figures which showed that the number of Covid deaths was doubling roughly every two weeks.

She added: “Generally, it takes four weeks from infection to death. So that means for the next four weeks everybody who is going to die probably already has Covid.

“We know that cases have been pretty much doubling every two weeks up until now and we know that hospital admissions have been as well.

“And that means that by 5 November we might expect this to double. Perhaps slightly lower if transmission has slowed slightly.”

She said that if the cases continue to double, we could be looking at 6,000 more deaths by 19 November and added that “there is not much we can do about it.”

“But if we can reduce transmission now, like right now, then we can save lives by 3 December and that is really what the circuit breaker is about.”

She presented a graph to the briefing highlighting the expected reduction in Covid-19 cases if a circuit breaker was introduced now or in two weeks’ or four weeks’ time.