NHS unable to trace contacts of 33% of people with coronavirus

Tracers took details from 5,407 of 8,117 people who tested positive in scheme’s first week in England

A third of those who have tested positive for the coronavirus in England have not provided details of people they have been close to and may have infected, data from the first full week of the new contact-tracing scheme has revealed.

Dido Harding, the chair of the NHS Test and Trace service, said she was heartened by the public’s willingness to cooperate, but the scheme would need to do better. Of the 8,117 positive cases referred to contact tracers, they had succeeded in reaching 5,407 who had been willing to give them names and phone numbers for the people they had met in the previous two days.

Q&A

What is contact tracing?

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 tracers had reached 85% of those contacts – 26,985 people – and asked them to self-isolate. There were a further 4,809 that they either failed to reach or failed to persuade to stay at home.

But Lady Harding said the programme was in its very earliest stages and she accepted that there was much still to do.

“Tens of thousands of people have engaged with NHS Test and Trace in its first week, either by taking a test if they’ve got symptoms or sharing their contacts if they test positive and then following the advice to self-isolate if they’ve been contacted. We clearly have got more to do to make sure that we reach everyone.”

The health secretary, Matt Hancock, said he was pleased with the way test and trace had worked in its first week. “It’s already had a huge impact: the system is working well, and as we’ve both said from the start, we’ll keep improving it. It will keep getting better,” he said.

Speaking at the daily Downing Street press briefing, he repeated his message that it was the public’s “civic duty” to comply with requests from contact tracers.

However, Hancock also underlined the scale of the challenge when he said the ongoing Office for National Statistics study of the prevalence of the coronavirus in the community has shown that as many as 70-80% of those who test positive have no symptoms.

Asked about the NHSX coronavirus app, originally slated for launch in mid-May, Hancock played down its significance, saying, “the app will help, and we’ll bring it in when it is right to do so”.

He also acknowledged that further easing of lockdown restrictions will depend on how successful the new system is. “The better test and trace is, the more lockdown measures we can relieve safely.”


“We’ve got a lot more to do to improve the speed of the entire service,” Harding said, “but actually we have really significant testing capacity and the single biggest thing we can do to improve the process is actually encourage anyone with symptoms to get a test.”

Tracing graphic 1

There were many reasons why the contacts of a third of those who tested positive could not be tracked down, she said. Sometimes the phone numbers and emails that contact tracers had been given were wrong. Sometimes people did not answer their phones or emails and sometimes people refused to tell the contact tracers who they had been spending time with.

“Interestingly, some people said to us: well, I’ve already told my mates that I tested positive so I don’t need you to,” Harding said.

Tracing graphic 2

Prof John Newton, the director of health improvement for Public Health England, who heads the testing and tracing programme, said they had to ensure they had the correct details for those people with a positive test.

“I think the key point for us in the 33% is we need to make sure when people apply for a test, we need to double check that we’ve got the right information from them that’s valid, so that when we come to go back to them, we can make contact. Those things are being improved all the time.”

Tracing graphic 3

Harding said she could not at this stage break down the numbers to reveal how many people had refused to self-isolate. Critics have voiced concern that some will not be able to afford to give up work for two weeks, but Harding stressed that financial support was available.

The 8,117 people referred to the contact-tracing service after testing positive is a lower number than the government website claims had tested positive in that week, 28 May–3 June, which was around 13,000. Newton said their numbers were only for England, and that some of the positive tests displayed online referred to individuals who might have had more than one test.

Prof Keith Neal, emeritus professor of the epidemiology of infectious diseases at the University of Nottingham, said: “Being unable to contact 33% of diagnosed cases is a concern particularly as a mobile number is involved in requesting the test.

“An absolutely crucial part of the test and trace system is the public committing to it – the system can not work without the public’s involvement.”


Mark Harris, a professor of virology at the University of Leeds, said it was surprising that contacts were being asked only to self-isolate.

He said: “Why are they not being tested, as is undertaken in other countries? By testing contacts we will also be able to identify other infected individuals and broaden the scope of the contact tracing to the next tier of contacts. This will help in identifying potential foci of infection and possibly inform localised lockdown strategies.”

Hancock said: “NHS Test and Trace is a new service on a scale never seen before, designed to help us control and contain this virus, and save lives.

“Backed by our rapid expansion of testing across the country, the new data shows how we are already helping to stop the spread of the virus with thousands of people booking a test, isolating and sharing their recent close contacts.

 “The service is key to helping us to return to a more normal way of life. We need everyone’s support and collaboration to ensure that we can continue to keep infections falling.”