Experts yesterday questioned a highly pessimistic report claiming that England may be hit by Omicron in May, causing as many as 75,000 deaths.

A study by London School of Hygiene and Tropical Medicine warned that there will be a significant increase in cases of this variant in the country without more severe measures.

Experts warned, however, that they felt the report had been ‘rushed out’ and was based on ‘sketchy data’ as it is still unknown how severe infection by Omicron actually is – although initial indications from South Africa suggest it may be milder than previous strains.

Similar estimates were made in April by the same school about the potential impact of summer lockdown restrictions. The forecaster was wrong, however.

They warned against lifting restrictions and predicted there would be ‘a resurgence in admissions and deaths comparable to the magnitude of the second wave in January’, when there were more than 1,000 deaths a day.

The LSHTM made significant adjustments to their forecasts as they became more precise data available.

Then, under their more ‘realistic scenario’, they predicted 1,000 hospital admissions and fewer than 200 deaths per day.

Only 71 deaths were recorded in England on July 19, when the lockdown was lifted. The death toll rose steadily over the next few months, reaching a peak of 153 deaths on October 28.

LSHTM Forecasters were bleakly predicting that there would be 492,000 deaths and approximately 75,000 hospitalisations by April’s end. This was based on the Omicron virus having ‘high immune escape’ – ie evading existing immunity to earlier Covid-19 variants – and a lower effectiveness of boosters.

Their most optimistic estimate is that there will be 175,000 hospitalsisations and 24,700 death.

The figures are based on Omicron’s immune response, which is highly effective. Boosters also prove to be very effective. LSHTM said ‘the team estimates that stronger measures may be required to keep the peak number of hospital admissions below the January 2021 peak’.

Dr Rosanna Barnard, from LSHTM’s Centre for the Mathematical Modelling of Infectious Diseases who co-led the research, said: ‘There is a lot of uncertainty about the characteristics of Omicron, and whether Omicron in England will follow the same course as it has in South Africa… Our most pessimistic scenario suggests that we may have to endure more stringent restrictions to ensure the NHS is not overwhelmed. Mask-wearing, social distancing and booster jabs are vital, but may not be enough.’

The study is important because the LSHTM contributes to Sage, the Government’s scientific advisory body, which will take its findings into account.

Scientists admit that their estimate of Omicron’s impact was compiled without knowing all the details. It has also not yet been peer reviewed – subjected to scientific scrutiny by independent scientists – the gold standard of scientific research.

Paul Hunter, a professor of medicine at University of East Anglia pointed out a Friday report by the UK Health Security agency indicating that boosters have high efficacy of 70% to 75%. Due to that, the LSHTM’s ‘most pessimistic projections’ are already out of date and unlikely to come to pass, he said.

He added: ‘Any model is only as good as its assumptions and one key assumption in this model is that severity of disease outcomes for Omicron is the same as for Delta in unvaccinated people.

‘Although we will not know for certain for a few weeks, indications from South Africa do suggest that Omicron does cause less severe disease than Delta.’

Professor Mark Woolhouse of Edinburgh University said: ‘These should not be regarded as firm predictions given that there is still considerable uncertainty about several key parameters, particularly regarding the severity of disease… At the moment, we have only sketchy data.’

Professor Carl Heneghan, of Oxford University’s Centre for Evidence-Based Medicine, told The Sunday Express: ‘This paper has been rushed out.’

The academic added: ‘How can we still be following modelling advice which has consistently been shown to be wrong?’