The re-designed NHS contact-tracing app, which begins trials in the Isle of Wight, will correctly identify seven out of 10 people who spend more than 15 minutes within 2 metres of another app user who has tested positive for coronavirus and warn them to self-isolate.
The new app has been designed in collaboration with Google, Apple and other tech companies so that it works with 99% of phones. It no longer has the major failing of the original which did not work with iPhones.
But it will struggle to compute the precise 2-metre boundary that is considered to be a safe distance from someone with the virus. Many people will be told they should self-isolate even though they spent 15 minutes just slightly further away – for instance 2.1 metres.
Contact tracing is one of the most basic planks of public health responses to a pandemic like the coronavirus. It means literally tracking down anyone that somebody with an infection may have had contact with in the days before they became ill. It was – and always will be – central to the fight against Ebola, for instance. In west Africa in 2014-15, there were large teams of people who would trace relatives and knock on the doors of neighbours and friends to find anyone who might have become infected by touching the sick person.
Most people who get Covid-19 will be infected by their friends, neighbours, family or work colleagues, so they will be first on the list. It is not likely anyone will get infected by someone they do not know, passing on the street.
It is still assumed there has to be reasonable exposure – originally experts said people would need to be together for 15 minutes, less than 2 metres apart. So a contact tracer will want to know who the person testing positive met and talked to over the two or three days before they developed symptoms and went into isolation.
South Korea has large teams of contact tracers and notably chased down all the contacts of a religious group, many of whose members fell ill. That outbreak was efficiently stamped out by contact tracing and quarantine.
Singapore and Hong Kong have also espoused testing and contact tracing and so has Germany. All those countries have had relatively low death rates so far. The World Health Organization says it should be the “backbone of the response” in every country.
Sarah Boseley Health editor
The designers of the app are understood to believe, from some 100,000 simulations, that this margin of error is acceptable, on the basis that people who were that close may still be at risk.
The trial which started on the Isle of Wight on Thursday will next week be extended to the London borough of Newham, to test its performance in one of the most diverse populations in the country. It will also be offered to NHS volunteer responders across England.
The new app is not a cut-down version of failed earlier attempts, but has more features, say government sources, who hope it will win the public’s trust and confidence. The contact-tracing element will depend on substantial numbers of people downloading it.
“It’s really important that we make it as easy as possible for everyone to engage with NHS test and trace. By launching an app that supports our integrated, localised approach to NHS test and trace, anyone with a smartphone will be able to find out if they are at risk of having caught the virus, quickly and easily order a test, and access the right guidance and advice,” said Dido Harding, executive chair of the NHS test and trace programme.
Simon Thompson, managing director of the app, said it was vital to controlling the spread of coronavirus and designed to give people maximum freedom at minimum risk.
“We have worked with some of the most innovative organisations in the world, such as Apple, Google, scientists from the Alan Turing Institute and Oxford University and governments across the world to come up with a state-of-the-art product which works to protect people everyday. It’s like NHS test and trace in your pocket,” he said.
“By giving access to the Isle of Wight, Newham and NHS volunteers first we can make this app even better before rolling out nationwide so the rest of the nation can benefit.”
The app will track the virus, not people, the government insists, anxious to avoid issues over data privacy. User data will not be centralised, as was the earlier plan, but will stay in the phone and can be deleted at any time. People using the app will get a warning to self-isolate if they have been near another app user with coronavirus, but they will not be contacted or monitored for their compliance.
If the contact is somebody in their family or at work, however, it is likely they will separately get a call or a visit from the contact tracing teams.
“There is no silver bullet when it comes to tackling coronavirus,” said Harding. “The app is a great step forward and will complement all of the work we are doing with local areas across the country to reach more people in their communities and work towards our vision of helping more people get back to the most normal life possible at the lowest risk.”
The app will also allow owners of venues such as pubs and restaurants to obtain and print a QR code that app users can scan on their phones when they visit. If there is subsequently an outbreak at the venue, app users can be alerted.
There is also a symptom checker, which will alert the user to self-isolate if they are suffering from one of the major known four symptoms of Covid-19, and a countdown function and advice for those told to self-isolate.
The latest test and trace data showed the service reached 79% of all those who tested positive, and 83.4% of their contacts where contact details were provided. The government says that is “in line with the recognised metric of success for contact tracing services across the world”.
However, critics say the system needs to do better if it is to keep the virus in check ahead of schools going back and then the winter months when people will socialise indoors.
