Those who have been in contact with someone who has tested positive for coronavirus will have to self-isolate for 10 days instead of 14, starting from Monday.
Those required to quarantine after returning from countries which are not on the travel corridor list will also see their isolation period reduced the same, in an approach agreed by all four nations.
The changes were announced by the UK’s chief medical officers and will come into force in England, Scotland and Northern Ireland from 14 December. It already applies in Wales.
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The reduction in the period follows a review of the current available evidence by England’s chief medical officer, Professor Chris Whitty; Scotland’s chief medical officer, Dr Gregor Smith; Northern Ireland’s chief medical officer, Dr Michael McBride and Wales’s chief medical officer Dr Frank Atherton.
The health chiefs said in a joint statement that following a review of the evidence, they were “confident” that the self-isolation period could be shortened.
“Self-isolation is essential to reducing the spread of COVID as it breaks the chains of transmission,” said the four CMOs.
“After reviewing the evidence, we are now confident that we can reduce the number of days that contacts self-isolate from 14 days to 10 days.
“People who return from countries which are not on the travel corridor list should also self-isolate for 10 days instead of 14 days.
“People who test positive should continue to self-isolate for 10 days from onset of symptoms or 10 days from point of taking a positive test if asymptomatic.”
They added: “We urge everyone to self-isolate when appropriate, it will save lives.”
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The new rules already apply in Wales following an announcement by the Welsh government earlier this week.
NHS Test and Trace will tell people to self-isolate for 10 days from Monday, but due to the time taken to develop technical changes, the NHS COVID-19 app will only do the same from Thursday.
Dr Jenny Harries, England’s deputy chief medical officer, said the science is based on the accumulation of evidence throughout the pandemic.
“SAGE, the Scientific Advisory Group for Emergencies, looked at this, as well as a number of academic institutions,” she told Sky News.
“All of those combined together showed that the tail-end of infectiousness is when an individual is less likely to infection.
“So allowing somebody out of self-isolation a short time earlier than that is a reasonable balance between managing the risk to the public, but allowing us not to intrude on their lives.”