Coronavirus: How does the NHS test-and-trace system and app work?

  • Published
Related Topics
Woman looking at her phone and wearing a maskImage source, Getty Images

Self-isolation rules are changing in some parts of the UK for fully vaccinated adults and children under 18.

If they are identified as a close contact of someone who's tested positive for Covid, they may soon be able to take a PCR test rather than self-isolate for 10 days.

When must I self-isolate?

You must self-isolate for 10 days if you:

  • test positive for Covid-19
  • live with someone who tests positive
  • are approached by text, email or phone by contact tracers who identify you as a close contact of someone who has tested positive
  • arrive in the UK from a red list country
  • arrive in the UK from France
  • arrive from any other amber list country and you are 18 or over, and have not been vaccinated

You must also self-isolate if you or someone you live with has Covid symptoms. You can stop self-isolating if the person with symptoms gets a negative PCR result.

Each UK nation has its own contact-tracing service:

When people test positive for coronavirus, they are asked to provide details of their close contacts. These include:

  • people they've spent at least 15 minutes with, at a distance of less than 2m (6ft)
  • sexual partners, people they live with or have had face-to-face conversations with, at a distance of less than 1m (3ft)

If you are deemed a close contact, other people in your household don't have to self-isolate unless you or they develop symptoms.

What if I'm fully vaccinated?


From 9 August, fully vaccinated adults identified as close contacts of someone who tested positive for Covid will no longer have to self-isolate for 10 days.

Instead, if they have no symptoms and at least two weeks have passed since the second dose, they can get a PCR test. If the result is negative, self-isolation can then be ended.

First Minister Nicola Sturgeon announced a similar change - with a negative PCR result - for people aged 17 or under. Children under the age of five will be encouraged, but not required, to take a PCR test.


From 16 August, fully vaccinated adults and all under-18s contacted by NHS Test and Trace (not the app) will be advised to take one PCR test as soon as possible.

As long as that is negative, and they don't develop symptoms, they won't need to take further action.


Similar changes will happen in Wales from 7 August. However, people will be also advised to take PCR test on day two and day eight, whether they are fully vaccinated or not.

Northern Ireland

Ministers in Northern Ireland are expected to discuss changes on 12 August.

What if I am not fully vaccinated?

Any adult not fully vaccinated will still need to isolate if they are identified as contacts.

Anyone who tests positive - regardless of age, vaccination status, or whether or not they have symptoms - will also still need to self-isolate.

What if I'm alerted by the NHS Covid app?

The NHS Covid app is available to download in England and Wales.

If you have the app, and you spend enough time close to another person using it, you will receive a "ping" alert if they later test positive for Covid.

You need to be within 2m (6ft) of them for 15 minutes to trigger the alert.

Northern Ireland and Scotland have separate apps.

Do I have to self-isolate if I'm pinged?

If you are "pinged" you're advised - but not legally obliged - to self-isolate for 10 days.

Government ministers have said it is "crucial" that people self-isolate when sent an alert.

However, it's feared that the large number of people being alerted has led to many users deleting the app.

How is the app changing?

Currently, when someone tested positive but had no symptoms, the NHS Covid app went back five days before the test, and alerted any close contacts during that time.

However, the app will soon only alert close contacts from the previous two days before the positive test.

The sensitivity of the app itself has not changed, and anyone testing positive will still have to self-isolate.

In the week to 28 July, nearly 396,000 people in England and Wales received alerts from the app, a sharp drop from 690,000 the week before.

Can I be exempt from self-isolation?

In England, employers providing critical services can now request an exemption for named employees who are fully vaccinated. Sectors include energy and emergency services.

Supermarket depot workers and food manufacturers are among those exempt from quarantine rules whatever their vaccination status.

Will I be paid if I'm told I have to self-isolate?

A £500 grant is available in England to people on low incomes who have to self-isolate. This includes parents who can't work because their child has to self-isolate. However, many applications have been turned down.

In Scotland people can apply for the Self-Isolation Support Grant, worth £500, and there is a similar scheme in Wales. In Northern Ireland a discretionary payment is available.

You may also be entitled to Statutory Sick Pay, which is worth £96.35 a week, or more if your employer has a sick pay scheme.