Sen. Lindsey Graham, R-S.C., said he tested positive for COVID-19 despite being vaccinated, becoming at least the third member of Congress to recently report an infection.

Graham tweeted he began having "flu-like" symptoms Saturday and saw a doctor Monday.

"I feel like I have a sinus infection and at present time I have mild symptoms," he said.

Graham, 66, said he will quarantine for 10 days, likely taking him out of the Senate for the votes on the bipartisan infrastructure plan he helped negotiate. And, as the ranking Republican on the Senate Budget Committee, he would be expected to lead GOP opposition to the budget resolution Democrats also expect to debate before the August recess.

In an evenly divided Senate, the absence of just one senator can dramatically alter the prospects for legislation.

Graham's diagnosis came as efforts to control the spread of the virus have become a renewed source of controversy in the Capitol. House Republicans have pushed back against a decision by Congress' chief physician to mandate masks in the chamber. The Senate does not have such a requirement, and Graham along with many other senators have been working without masks.

Two House members recently said they tested positive for COVID, and several staff members also have been infected.

Graham said he was "very glad" he was vaccinated.

"Without vaccination I am certain I would not feel as well as I do now," Graham tweeted. "My symptoms would be far worse."