UK's centralised COVID-19 app will offer more insight, says programme head

The COVID-19 smartphone app being developed by Britain will be able to give serious insights into the virus by virtue of using centralised matching, despite its offering less privacy than rival apps, the head of the programme said. Countries are rushing to develop apps which, along with a wider testing and tracking programme, are seen as key to easing social distancing rules that have all but shut global economies.

Britain has opted for a centralized model, whereby a list of contacts made via bluetooth signals is stored on a users' device as anonymous tokens. If the user has symptoms or tests positive for COVID-19, the list of contacts can be submitted to the app, which analyses the data and notifies devices matching the tokens it deems at risk, for example, because of the time the devices were in proximity.

Rival systems, including one proposed by Apple and Google, match the lists of tokens on the devices themselves, removing the risk of sending data to a centralized server, even if it is anonymized. "If privacy was the only thing we were optimizing for here, then it may well be that a decentralized approach should be the default choice," Matthew Gould, chief executive of the National Health Service's technology group NHSX, told a parliamentary committee on Monday.

But privacy had to be balanced against public health, he said. "It was our view that a centralized approach gave us the potential ... to collect some very important data that gives serious insight into the virus that will help us," he said.

The insights a centralized approach could bring include data on which symptoms develop into COVID-19, which contacts are riskier, and the difference, for example, between a contact three days ago and one yesterday, he said. He added that Britain was talking to international partners and was also working "phenomenally closely" with Apple and Google.

"We are not in competition, we are all trying to get this right," he told the committee.