People in England who have been fully vaccinated will from August 16 no longer have to self-isolate after close contact with someone who tests positive for COVID-19.
The same policy will also apply to children, UK health minister Sajid Javid said on Tuesday.
Prime Minister Boris Johnson set out plans on Monday to end social and economic COVID-19 restrictions in England on July 19, a test of whether a rapid vaccine rollout offers enough protection from the more infectious Delta variant.
Javid said the success of the vaccine programme meant it was possible to go further in easing self-isolation rules for those who have received both shots.
"From the 16th of August ... anyone who's a close contact of a positive case will no longer have to self-isolate if they have been fully vaccinated," Javid told parliament.
"In line with the approach for adults, anyone under the age of 18 who is a close contact of a positive case will no longer have to self-isolate."
Only those contacts who themselves test positive will be required to self-isolate, he said.
Johnson is betting that the vaccination programme, which has weakened the link between infections and hospital admissions, can prevent the health service from being overwhelmed by a new wave of COVID-19.
Javid, appointed late last month after Matt Hancock quit as health minister, has underlined the importance of other health issues, economic problems and education challenges that have build up during the pandemic.
Critics say Johnson and Javid have abandoned a pledge to take a cautious approach to lifting restrictions.
Javid said that by the time restrictions are lifted on July 19, there could be 50,000 COVID-19 cases a day -- double current rates -- and that cases "could go as high as 100,000."
Britain reported 27,334 new cases on Monday, and 64 per cent of the population have now had both vaccine doses.