Health Secretary Sajid Javid, says he has tested positive for Covid-19 and is suffering "very mild" symptoms.
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.
Meanwhile, England's deputy chief medical officer, Prof Jonathan Van-Tam, has warned of a "bumpy winter" ahead.
It comes as the UK recorded more than 50,000 daily cases for the second day running, days before almost all legal restrictions on social contact are lifted in England on Monday.
There were 54,674 cases - following 51,870 new cases on Friday - with 41 deaths within 28 days of a positive coronavirus test.
The last time cases exceeded 50,000 was in 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.
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.
Mr Javid previously tweeted that he had received the Oxford-AstraZeneca vaccine.
A Public Health England study found two doses of the AstraZeneca vaccine was 60% effective at stopping symptomatic disease from the Delta variant, which is now dominant across the UK. Two jabs of the Pfizer vaccine was 88% effective.
A separate analysis from PHE found the vaccines were highly effective against preventing hospitalisations from the same variant, with two doses of the Pfizer jab 96% effective and the AstraZeneca jab 92%.
England's deputy chief medical officer, Prof Jonathan Van-Tam, said vaccines were not 100% effective but were likely to have saved about 30,000 lives in the UK.
He told the BBC: "We still need to keep going with these vaccines because they've completely changed the landscape in terms of the numbers of people going into hospital and, very much so, the numbers of people dying. They're still a massive success."
Lateral flow tests provide a quick result, using a device similar to a pregnancy test and are intended for use in those without symptoms, according to the NHS. PCR tests are mainly used when people have coronavirus symptoms or have already had a positive lateral flow result, and are sent to laboratories to be checked. The NHS suggests people do a lateral flow test twice a week to check if they have the virus.
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 was a danger that England may have to go back into lockdown in the autumn if hospitalisation rates continued to increase during the summer.
Mr Hunt, a former health secretary, said the situation facing the NHS was "very serious".
"The warning light on the NHS dashboard is not flashing amber, it is flashing red," he told the BBC Radio 4 Today programme.
KNUST students ordered to leave campus by Saturday
V/R: Three arrested for police recruitment scam
E/R: Both male and female students of Apeguso SHS share same pit latrine
Your hypocrisy over economic statistics annoying – Mahama to economic experts
Rasta student quits Achimota for GIS following AG’s appeal
CID petitioned over WASSCE leakage
Western Region Minister denies asking MMDAs for funds for father’s funeral
Let’s deal decisively with political situation in Guinea – Akufo-Addo urges ECOWAS leaders
Africa faces 470 million COVID-19 vaccine shortfall in 2021 -WHO
Harruna Attah writes: In fairness to Rawlings…