From tomorrow ( Tuesday 14th December ) the guidance is changing again.

 

The new rules are:

• people who are fully vaccinated and identified as a contact of someone with COVID 19 - whether Omicrom or not, should take an NHS rapid lateral flow test every day for 7 days to help slow the spread of COVID 19.
• Unvaccinated adults must continue to self isolate for 10 days if they are a contact of someone with COVID 19.

This follows a significant rise of Omicrom cases in the UK and this variant is expected to become the dominant strain by mid December 

 

https://www.gov.uk/government/news/daily-rapid-testing-for-covid-19-contacts-launches-this-week.