Coronavirus: 19 million people in UK ‘likely to have been infected already’, study finds

University of Manchester study claims 29 per cent of British population may already have had the disease – but sceptics urge caution over findings

Around 19 million people in the UK could have already been infected with the coronavirus, new research suggests.

A team of researchers from the University of Manchester, Salford Royal and Res Consortium have estimated that 29 per cent of the British population is “likely” to have had the virus by now.

The new study, published in the International Journal of Clinical Practice, is the first to use local authority “R” transmission rate data to attempt to assess the full impact of infection since the Covid-19 outbreak began.

Dr Adrian Heald from the University of Manchester said: “Covid-19 is a highly infectious condition and very dangerous for a small group of people. However a much larger group seem to have low or no symptoms and have been unreported.”

He added: “This study tries to provide an estimate of the number of historic infections – and gives us all a glimmer of hope that there may be light at the end of the tunnel.”

The research team said their findings suggested a significant percentage of the UK population had been infected without falling seriously ill.

Mike Stedman from Res Consortium, who carried out the data analysis as part of the Manchester University-led research, conceded: “The figures are not perfect, with the numbers of severely ill patients as a proportion of the total cases being used as a market for estimates of wider infection.”

He added: “Only extensive antibody testing could give us a more accurate picture – but as that is only just becoming available, we believe this form of modelling is important in informing the best approach to unlocking the population.”

Although the University of Manchester paper was peer reviewed, several independent experts pointed out potential flaws in the study.

Dr Konstantin Blyuss, Reader in Mathematics at the University of Sussex, said trying to make estimates for the whole country based on local R rates of reproduction was problematic.

“The value of R is notoriously difficult to estimate, and as a result, the estimates always have a wide margin of error, which means that it is almost impossible to rely on accurate estimates of R for any significant population-wide conclusions.”

Dr Adam Kucharski, associate professor in infectious disease epidemiology at the London School of Hygiene and Tropical Medicine, said: “it is likely that there is huge uncertainty in the estimates produced by the model used in this paper.”

He pointed out “how difficult it is to estimate the extent of unreported cases in a population from reported cases alone”, adding: “Given how much antibody data is now emerging, it is increasingly important to focus on measurements rather than just modelling estimates.”

It comes as optimism builds over a “game-changer” new antibody test developed by the Swiss company Roche, allowing health professionals to check whether people had previously been infected with the coronavirus.

Public Health England approved the test and said it carried a 100 per cent success rate in excluding false positives, and deputy chief medical officer Professor Jonathan Van-Tam said it could be rolled out in the UK the “days and weeks to come”.

Boris Johnson’s official spokesman added to the optimism by saying it could lead to “some kind of health certificate” allowing more people to feel safe returning to work.

However, independent experts have raised doubts about the scale of the potential benefits of the tests and called for more transparency.

“Without seeing the study methods and the data it’s impossible to verify these claims of accuracy,” said Professor Carl Heneghan, director of the Centre for Evidence-Based Medicine at the University of Oxford.