Javid, who has been health secretary for three weeks, has backed Prime Minister Boris Johnson's plan to scrap all remaining legal coronavirus restrictions from Monday, despite a fresh surge of cases fuelled by the highly transmissible Delta variant.
"This morning I tested positive for COVID," Javid said in a tweet, adding he had first taken a rapid lateral flow test, and then later his positive result was also confirmed in a PCR test, which needs processing in a laboratory.
"My positive result has now been confirmed by PCR test, so I will continue to isolate and work from home."
Javid tweeted on March 17 that he had received a first shot of Oxford/AstraZeneca's (AZN.L) COVID-19 vaccine, posting a picture of him getting a second dose on May 16.
Vaccines are not 100% effective at preventing infection, but fully-vaccinated people are less likely to get seriously ill with COVID-19 even if they can test positive.
Real-world analysis published by Public Health England has found that two doses of the AstraZeneca vaccine are 60% effective against symptomatic disease from the Delta variant and 92% effective against hospitalisation.
Britain is facing a new wave of cases of COVID-19, but Johnson and Javid claim the vaccine programme has largely broken the link between COVID-19 cases and mortality, although Johnson has said that the country should reconcile itself to the prospect of more deaths from COVID.
Britain has the seventh highest COVID-19 death toll in the world, and has fully vaccinated two-thirds of adults, although it is not vaccinating children.
Some scientists have warned that the government's reopening plans for England are dangerous given the significant number of people who remain unvaccinated and the fact that vaccines are not 100% effective. read more Reporting by Alistair Smout; additional reporting by Kanishka Singh; Editing by Catherine Evans, Christina Fincher and Daniel Wallis