Health Secretary Sajid Javid says he has tested positive for Covid-19, but has had two jabs and his symptoms are "very mild".
Mr Javid, who became health secretary in June, said he had taken a lateral flow test after feeling a "bit groggy" on Friday night and it was positive.
He said he was now self-isolating until he got the results of a PCR test.
On Friday, the UK recorded more than 50,000 daily cases for the first time since mid-January.
In a video posted on his Twitter feed, Mr Javid said: "I was feeling a bit groggy last night, so I took a lateral flow test this morning and it's come out positive, so I'm now self-isolating at home with my family until i get the results of a PCR test."
"I'm grateful that I've had two jabs of the vaccine and so far my symptoms are very mild."
He urged people who had not been vaccinated yet to "get out there and get them as soon as you can".
Mr Javid also said people who feel groggy or come into contact with someone who is positive should take a lateral flow test.
"If everyone plays their part, you're not only protecting yourself and your loved ones but you're also safeguarding the NHS and helping to preserve our way of life," the health secretary added.