A Microsoft Excel error which caused positive Covid-19 results to go missing has been linked to 1,500 excess deaths, researchers have suggested.
Thiemo Fetzer and Thomas Graeber of Warwick and Harvard universities, respectively, examined the impact of the glitch, which affected positive cases in late September and October.
The lost cases meant that 16,000 contacts of people who had tested positive for Covid-19 were either missed or contacted with a delay.
According to the researchers, the data on Covid-19 cases and deaths indicate that the glitch “propelled England to a different stage of pandemic spread”.
Public Health England has disputed the researchers’ estimates, calling them “misleading”.
Although Fetzer and Graeber agreed that the 1,500 deaths figure is just an estimate, they note that the paper is “strong” evidence for the value of contact tracing.
Speaking on the findings, Professor Fetzer said: “many parts of England had suffered from the failure to refer cases to test and trace in a timely fashion, but some regions were, by chance, more strongly affected.”
About half of the missing cases were in either the North West or in Yorkshire and the Humber, he said.
From late September to early November, these areas saw about 3,000 Covid-19 deaths, just under half the total for England.
Fetzer and Graeber estimate about 20 per cent of these deaths could be attributed to the Excel glitch.
Despite uncertainty around the exact size of the effect of the glitch, the research points to the value of contact tracing, the researchers said.
Around the time of the Excel error, from late September to November, only about half of the contacts of positive cases were contacted within 24 hours.
That number has improved, hovering at about 70 per cent in the most recent three weeks for which data are available.
Isabel Oliver, the director of Public Health England’s national infection service, said in a statement to The Guardian: “These are misleading estimates. It’s not appropriate to conclude that an increase in cases and deaths at the time was caused by this issue and the authors themselves accept that there is low confidence in their conclusions.
“Our own analysis of the data suggests that the delay in the upload of data files coincided with the increases in cases linked to the return to university and the epidemiological trends we were already seeing in parts of the country.”
“The majority of cases affected by this issue were also contact traced within five days, which means it is unlikely the delay led to their close contacts transmitting the virus unknowingly given typical incubation periods,” Oliver concluded.