Shutting schools during the Covid-19 pandemic could actually increase the overall death rate from the disease, researchers have warned.

Researchers from the University of Edinburgh used a model called “CovidSim”, which replicates simulations of people in the UK population as they travel to school, work, home, university and hospital.

They used the model to examine various interventions, including social distancing of the over-70s, social distancing of the entire population, closure of schools and universities, and at-home isolation of people who develop symptoms - for seven days and 14 days.

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They wrote: “The findings of this study suggest that prompt interventions were shown to be highly effective at reducing peak demand for intensive care unit (ICU) beds but also prolong the epidemic, in some cases resulting in more deaths long-term.

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“This happens because Covid-19-related mortality is highly skewed towards older age groups.

“In the absence of an effective vaccination programme, none of the proposed mitigation strategies in the UK would reduce the predicted total number of deaths below 200,000.”

The researchers point out that when the interventions are lifted, there is still a large proportion of the population susceptible and a substantial number still infected.

“This then leads to a second wave of infections that can result in more deaths, but later,” they wrote.

The researchers were reassessing the findings of researchers from Imperial College London, published in Report 9, which prompted the far-reaching social restrictions implemented in March - including the closure of schools for most pupils. 

That study also found that closing schools reduced the reproduction number of Covid-19 but had the unexpected effect of increasing the number of deaths.

Graeme Ackland, professor of computer simulation from the University of Edinburgh’s School of Physics and Astronomy, who led the study, said: “In the short-term, closing schools contributed to reducing the severity of the first wave, to the extent that Nightingale hospitals were not needed, but the decision has left us more vulnerable to subsequent waves of infection.

“Mitigating a Covid-19 epidemic requires very different strategies for different age groups and a different strategy from an influenza epidemic, with more focus on shielding elderly and vulnerable people.”

However, Mark Woolhouse, professor of infectious disease epidemiology at the University of Edinburgh, said: “The headline result - that school closures in March could lead to a larger death toll over time - is intriguing and may cause some concern. In fact, this result applies to a specific, and probably unrealistic, scenario and should not be interpreted as a prediction.

“Nonetheless, this counterintuitive result does shed some light on the current debate about whether to allow herd immunity to build up in age groups that rarely experience severe consequences of infection.”

A government spokesman said: “At every stage of our response we have been guided by the advice of experts and took decisive action from the outset to support the NHS and save lives.”