BREAKING: Defense Secretary Lloyd Austin tests positive for COVID-19

Austin said he tested positive Sunday morning for COVID-19 after he requested the test for exhibiting symptoms while at home on leave. "I am following my physician's directions," Austin added in the press release, noting that he will quarantine for the next five days in accordance with CDC guidelines.

"I have informed my leadership team of my positive test result, as well as the President. My staff has begun contact tracing and testing of all those with whom I have come into contact over the last week," Austin said Sunday.

Austin has been mocked for wearing a protective visor over a face mask during a diplomatic visit to Manila, in which critics resurfaced Sunday. The covered face of the US military boss in the Philippines sparked backlash at home back in July.

Austin said in the press statement he last met with President Joe Biden on Dec. 21, more than a week before he began to experience symptoms, and was last in the Pentagon on Thursday were he met briefly with a few staff members.

"As my doctor made clear to me, my fully vaccinated status — and the booster I received in early October — have rendered the infection much more mild than it would otherwise have been," Austin added, stressing: "And I am grateful for that."

He further touted vaccination in light of infection: "The vaccines work and will remain a military medical requirement for our workforce. I continue to encourage everyone eligible for a booster shot to get one. This remains a readiness issue."

Austin's positive test result follows a series of high-profile "breakthrough" cases including that of Sen. Elizabeth Warren and Rep. Ayanna Pressley.