In England, self-isolation rules following a Covid-19 contact will lift for the fully vaccinated from August 16, while Wales will make the change on August 7.
Scotland will lift its isolation rules on August 9, while Northern Ireland considering what stance to take.
But ministers deciding the rules in England have defended August 16 date, despite pleas from businesses, saying self-isolation remains an important tool for keeping Covid-19 infections down while the vaccination effort proceeds.
Asked if England should follow Wales and Scotland in bring the relaxation date forward, Transport Secretary Grant Shapps said every decision on coronavirus is constantly under review but suggested the government would stick with its original plan.
"One in three people who are asked to self-isolate do go on to develop coronavirus," the minster told ITV News, "so whilst the numbers are still relatively high, though we're pleased to see trending downwards, it is important to have this last ability just to try keep a lid on things".
"It's only two and a half weeks away and August 16 will be the point at which we're able to get rid of that."
Asked if the date is set in stone he told Sky: "Yeah, right now that is the date. We'll always keep these things under review but I don't want to open up false hope for you, it's not too far away now."
"The reality is that people putting themselves in self-isolation has been a factor in saving a lot of lives because it turns out that one in three people who are requested to self-isolate do end up developing symptoms, so it is, if you like, the only remaining measure that is being taken at the moment, because of course all the other measures have been dropped at the fourth unlock stage on the 19 July," Mr Shapps said.
Prime Minister Boris Johnson has also insisted England's August 16 date is “nailed on”.
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Sir Keir Starmer urged the government to follow other devolved nations after Wales's Labour First Minister Mark Drakeford confirmed August 7 as the day when double-jabbed adults can avoid isolation if they come into contact with a positive case.
Businesses have also been urging the government to lift isolation rules after a surge in people being "pinged" by the NHS app caused disruption to several sectors and reached a recent record level of almost 700,000 alerts sent to Covid app users in England and Wales.
Sir Keir Said: "This has been a summer of chaos for British businesses and British families." “The Tory government has never been able to explain the logic of their self-isolation rules and has just repeated the same mistakes over and over again.
He added: “The government’s slapdash approach to this global pandemic is crippling our economy and creating real problems for businesses and families alike. Welsh Labour has shown what can be done and it’s time for the Tories to do the same.” Wales’s change will come into effect on the same day the country is expected to move to alert level zero – when most coronavirus restrictions will be lifted.
Some frontline workers in England are already exempt from isolation, including those in prisons, waste collection, defence, the food industry, transport, Border Force and police and fire services.
Daily negative test results enable those eligible workers who have been alerted by the NHS Covid-19 app, or called by NHS Test and Trace as coronavirus contacts, to continue working.
Confirming the rule change for Wales, Mr Drakeford said: “Self-isolation on symptoms or a positive test result continues to be a powerful measure in helping to break the chains of transmission and stop the spread of the virus.
“It is important we retain this, even for people who have been fully vaccinated.
“But we know a full course of the vaccine offers people protection against the virus and they are far less likely to contract it when they are identified as close contacts.
“This means they no longer need to self-isolate for 10 days."