Amid the “alarming” spread of a more transmissible COVID-19 variant, British Prime Minister Boris Johnson has announced a new national lockdown in England.

During an address on Monday, Johnson said it’s “clear” that England must “go into a national lockdown” that’s “tough enough to contain” the new coronavirus variant, as it’s been “both frustrating and alarming to see the speed” with which it has been spreading.

“That means the government is once again instructing you to stay at home,” Johnson said.

Those in England are being ordered to only leave home for “limited reasons,” including to shop for essentials, exercise, seek medical assistance, escape domestic abuse, or go to work if working from home isn’t possible. Schools are also being instructed to move to remote instruction, “except for vulnerable children and the children of key workers.”

Johnson’s announcement came after the United Kingdom’s chief medical officers warned that the National Health Service could become overwhelmed in some areas within 21 days without new measures.

“I know how tough this is,” Johnson said. “And I know how frustrated you are, and I know that you’ve had more than enough of government guidance about defeating this virus. But now, more than ever, we must pull together. … The weeks ahead will be the hardest yet, but I really do believe that we’re that we’re entering the last phase of the struggle.”