Lindsey Graham, a senior United States senator from South Carolina, has become the first senator to have a breakthrough infection after being vaccinated against COVID, according to NBC 11 News.

On Monday, Graham said he is “very glad” that he received the vaccine, without which his current symptoms would have been “far worse.”

The 66-year-old said, “I feel like I have a sinus infection, and at present time, I have mild symptoms. I am very glad I was vaccinated because without vaccination, I am certain I would not feel as well as I do now. My symptoms would be far worse.”

He said he would be in quarantine for 10 days after being notified of his positive test.

A handful of senators have been urged to get tested as they spent part of the weekend working and socializing with Graham, who attended a gathering on Sen. Joe Manchin’s houseboat.

Spokesman Kevin Bishop said Graham was among the senators who attended Manchin’s event on Saturday.

Manchin’s spokesperson Sam Runyon said the West Virginia Democrat “is fully vaccinated and following the CDC guidelines for those exposed to a COVID positive individual.”

Sen. Manchin said he had since tested negative and said the event was “just trying to get people together.” He said, “We do everything in a bipartisan way, and that’s what we do. I talked to Lindsey today, he’s fine.”

It is unclear how risky it was for the people who were near Graham, irrespective of them being vaccinated or not.

The Centers for Disease Control and Prevention (CDC) says fully vaccinated people who have been in close contact with someone who has COVID-19 do not need to quarantine if they are asymptomatic; however, they should be tested within five days and wear a mask indoors for 14 days or until testing negative.

Graham was vaccinated in December and has long been a vaccine promoter, He said during a visit to the Medical University of South Carolina in Charleston, “The sooner we get everybody vaccinated, the quicker we can get back to normal.”