The PM says the closure of air travel corridors from 04:00 on Monday will apply across the UK.
This will initially happen for a month, although it will be kept under review and could be extended.
Anyone arriving in the UK must quarantine for 10 days or they have the choice of doing an extra test on day five to shorten the isolation.
Outlining the measures to come into place, he calls them “vital”, as “day by day, hour by hour” progress is being made in vaccinating people.
He adds that 3.2 million people across the UK have received vaccines.