MPs have criticised the government's test-and-trace system, saying that it's too expensive, and has had no clear impact on fighting the pandemic.
An estimated 22 million people in England have received at least one test since the system started in May 2020.
What is test-and-trace?
Test-and-trace, or contact tracing, is a system for identifying people who have been in close contact with someone who has caught Covid.
Those people are then asked to self-isolate for 10 days - even if they have no symptoms - to prevent the chance of passing the virus on, if they do have it.
Each UK nation has its own contact tracing service:
Why is it being criticised?
MPs on the House of Commons Public Accounts Committee said that test-and-trace is costing taxpayers £37bn over two years, but has made no "measurable difference".
Committee chairwoman Meg Hillier said the government had justified the huge expense because it was supposed to prevent more lockdowns.
This promise, she said, "has been broken, twice".
The committee also criticised the system's reliance on private consultants, some of whom cost more than £6,000 per day.
What is the government's response?
The government says the scheme is helping to reduce infection rates.
Transport Secretary Grant Shapps told the BBC that the MPs' report "defies logic", adding, "if we didn't have the test-and-trace system, we would have been in a much, much worse position".
Baroness Dido Harding, who's in charge of the system, has said that it had to be built from scratch, and was now doing more tests than any other comparable country.
How does it work?
People who have tested positive for coronavirus are contacted by app, text, email or phone.
They are asked to log on to a website and give personal information, including:
- name, date of birth and postcode
- who they live with
- places they visited recently
- names and contact details of people they have recently been in close contact with
Close contacts are:
- people you've spent 15 minutes or more with - at a distance of less than 2m (6ft)
- sexual partners, household members or people you have had face-to-face conversations with - at a distance of less than 1m
Contact must have taken place within a nine-day period, starting 48 hours before symptoms appeared.
What happens if I am contacted?
If you are approached because one of your contacts has tested positive, you must stay at home for 10 days from your last point of contact with them.
You must self-isolate, even if you don't have symptoms.
Others in your household don't have to self-isolate unless they also develop symptoms, but they must take extra care around you regarding social distancing and hand washing.
Refusing to self-isolate when told to is illegal in England, with fines ranging from £1,000 for a first offence to £10,000 for more serious breaches.
The law was changed after a study commissioned by the government found just 18% of people who had symptoms went into isolation.
What about sick pay?
The government's scientific advisers have warned that people will not self-isolate if it is likely to cause financial problems.
If someone is self-isolating but can't work from home, their employer must ensure they receive sick pay.
In September, the government introduced a £500 support payment for people on low incomes, who were unable to work because they were self-isolating.
However, BBC Reality Check reported that about two-thirds of those who applied for the payment had been turned down.
What about the contact tracing app?
There is also an NHS Covid app for people in England in Wales, which you can download on a modern smartphone (not on smart watches or tablets).
Phones must have:
- Android 6.0 (released in 2015) or iOS 13.5 (released in 2020)
- Bluetooth 4.0 or higher
- Some recent Huawei handsets will not load the app
What can the app do?
When two phones running the app are near each other, they will make contact through Bluetooth.
If they are close for a long enough time, and one of the two owners later shares a positive coronavirus test via the app, then the other will receive an alert.
You can also use the app to check in at venues - for instance, shops or places of worship.