Coronavirus test and trace system has launched in England
The test and trace system has launched in England.
The service helps to identify people who have been in close contact with someone who has tested positive for coronavirus.
Mr Johnson told the Liaison Committee that the track and trace system "will change people's lives."
"It will require a great deal of thought and compliance, and I think it will be worth it for the whole nation," he added.
Under the new system, those who test positive for coronavirus will be contacted by a member of the NHS Test and Trace team. They will then be asked to provide details of the people they have come in close contact with. This includes people from their household.
Anyone who is identified as being in close contact with someone who has tested positive for coronavirus will be asked to self-isolate for 14 days.
Responding to the query about whether it will be compulsory for those who have been contacted by the test and track team to stay at home, the prime minister warned that fines could be issued if people do not abide by the measures.
"We want people to understand that this is something that is not just good for them, but also good for the whole of society. We intend to make it clear to people they must stay at home."
"We will be asking people to stay at home, if they don't follow that advice what we will be saying is we will consider what sanctions may be necessary - financial sanctions or fines," he added.
Explaining how the scheme will work during the daily government briefing, Baroness Dido Harding, the Executive Chair of NHS Test and Trace, outlined the three steps which are involved:
1. If you have one or more of the symptoms of coronavirus - a fever, cough, loss of sense of taste or smell - you must isolate immediately.
2. You must then book a test on the NHS/coronavirus site or dial 999. If you test positive, you'll be contacted by NHS test and trace service within 24 hours.
3. The service will help you establish who you've been in contact with and you could have infected.