Health Secretary Sajid Javid says he has tested positive for Covid-19, but so far his symptoms are “very mild”.
Mr Javid, who said he had received both vaccine doses, took a lateral flow test on Saturday morning after feeling a “bit groggy” on Friday night and it came back positive.
He said he is now self-isolating until he gets 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 felt groggy or came 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.
Mr Javid replaced Matt Hancock as health secretary less than three weeks ago after CCTV footage emerged showing his predecessor kissing a colleague in his office in breach of social-distancing rules.
Earlier this week, Mr Javid made his first visit to a care home as health secretary at Aashna Care in Streatham, south London.
The home has a 100% vaccination rate among staff and residents, the majority of whom are from a black and minority ethnic background.
Boris Johnson and Mr Hancock both caught Covid-19 during the first wave of the pandemic in 2020, with the prime minister being admitted to intensive care at St Thomas’ Hospital in London after falling seriously ill.
The health secretary’s announcement comes as the government prepares to go ahead with the final lifting of lockdown restrictions in England on Monday.
Social-distancing rules will end, although government guidelines advise face coverings should still be worn in enclosed spaces such as in shops and on public transport, while pubs and bars should be table service only.
Jeremy Hunt, the chairman of the Commons health select committee, warned there is a danger that England may have to go back into lockdown in the autumn if hospitalisation rates continue to increase through the summer.
Mr Hunt, a former health secretary, said the situation facing the NHS is “very serious”.
On Friday, there were 51,870 cases recorded – the highest figure since 15 January – 49 deaths within 28 days of a positive test and 717 hospital admissions.
The seven-day average for each is up 34.9%, 57.4% and 43.4% respectively.
“The warning light on the NHS dashboard is not flashing amber, it is flashing red,” he told the BBC Radio 4 Today programme.