Scotland is escaping a "pingdemic" because its contact tracing app is less sophisticated than England’s and does not order people to self-isolate based on an algorithm, experts believe.
Despite a significant number of Covid cases in Scotland over recent weeks, only a tiny amount of people have been pinged in comparison to England and Wales, where the NHS app uses a complex matrix to calculate risk of exposure to the virus.
The cruder technology in Scotland defines a close contact only as someone who the app works out has been within two metres of a person who later tests positive for 15 minutes or more. However, in England factors including distance, infectiousness and length of exposure are taken into account in deciding whether someone is pinged.
Just 59,022 people have been told to self-isolate by Scotland’s app since its launch in September. Meanwhile, new figures released on Thursday showed that 618,903 pings were sent out in England and Wales in the week to July 14 alone.
This means that, taking differences in population size into account, almost as many people were pinged in a single week south of the border as have been during the whole pandemic in Scotland.
Over half a million 'pinged' at start of July
"The English app is more complex – it’s probably a wee bit more sensitive as well," Greig Paul, of the department of Electronic and Electrical Engineering at the University of Strathclyde, said. "The key difference is the Scottish one says ‘were you approximately within two metres for 15 minutes?’ If yes, ping, if no, no ping.
"The English one says ‘you were there within a metre of them for 10 minutes’, then you were three metres away for another length of time, then it adds up the risk together. It also considers what day, in relation to symptoms, the exposure was on. So the English app can catch situations the Scottish app would miss."
Despite concerns that the English app may be too sensitive, Dr Greig said figures from Downing Street, which suggested one third of people pinged went on to develop symptoms, suggested this was not the case.
He added: "Far fewer people are getting pinged in Scotland, but there are still significant numbers testing positive. So the Scottish one doesn’t seem to be yielding the same rate."
Dr Greig was backed by Jon Crowcroft, a computer scientist at the University of Cambridge, who said he believed the English app was accurate but called for the advice to people pinged to be overhauled to take account of factors such as vaccination status.
However, despite Scotland escaping a pingdemic there are concerns that the cross-border differences have exposed deficiencies in the technology, despite Nicola Sturgeon insisting the app is working well.
It is also estimated that as many as half of the two million people who downloaded the Scottish app are no longer using it. Unlike the English version, it is not used to check in at venues such as pubs and restaurants, meaning there is less of an incentive for people to keep it active.
Alex Cole-Hamilton, the Scottish Lib Dems’ health spokesman, said: "The fact that the Scottish app seems to be less sophisticated than its UK Government counterpart raises questions about whether cases have been missed that would have been picked up elsewhere.
"One of the things the inevitable public inquiry will have to explore is whether having a separate Scottish app was the right decision and whether anything could have been done to improve the performance of these tools."