Tom Williams | Pool | Reuters
Graham, 66, said in a tweet that the House physician notified him he tested positive despite being fully-vaccinated. The South Carolina Republican said he begun having flu-like symptoms Saturday night, and that he will be quarantining for 10 days.
While the Senate has not formally issued a mask mandate, Graham was reportedly seen wearing a mask on Monday, according to a Politico reporter.
Graham started to show symptoms when the Senate was in session over the weekend working on the bipartisan infrastructure bill. It is unclear how many other lawmakers in the Senate came in close contact with Graham.
Graham attended a Saturday night part aboard Democratic Sen. Joe Manchin’s houseboat, NBC News confirmed. The West Virginia senator’s office did not confirm whether Graham was there, but spokeswoman Sam Runyon said Manchin is fully vaccinated and “following the CDC guidelines for those exposed to a COVID positive individual.”
According to the CDC, these guidelines include testing three-to-five days after exposure to someone with confirmed or suspected Covid, and wearing a mask in public indoor settings for 14 days or until they test negative. Fully vaccinated individuals should also isolate if they test positive.
Graham was one of 17 Republican senators who voted to advance the infrastructure plan last week. His absence, or a potential quarantine for other senators, could affect passage of the bill if a final vote is closer.
While the Senate has not reinstated a mask mandate, House Republicans have strongly opposed a renewed mask requirement in their chamber. The House has more than four times as many members as the Senate and a larger share of unvaccinated lawmakers.
Graham’s announcement came as the United States contends with a surge of the delta variant of Covid, and as the Biden administration urges more people to get vaccinated.
The CDC on Thursday warned in a confidential document that the Delta variant, which is now the dominant form of the disease in the U.S., is as contagious as chickenpox and has a longer transmission window than the original Covid strain.
Health officials said Covid vaccines prevent more than 90% of severe disease, but may be less effective at preventing infection.
The confidential document, which was reviewed by CNBC, said that 35,000 symptomatic infections are occurring each week among 162 million vaccinated Americans.
Publicly available CDC data states that 5,914 fully vaccinated individuals had been hospitalized or died with Covid infections as of July 19. But health officials have also pointed out that the majority of people hospitalized or killed by Covid are unvaccinated, and that “breakthrough infections” among the vaccinated tend to be milder.
Data from a Monmouth University poll show a partisan split in Covid vaccine hesitancy.
The survey found 17% of respondents said they were likely opposed to getting the vaccine. Among them, 70% either identify or lean toward the Republican Party, while merely 6% identify with Democrats.
The Biden administration is continuing to push for more Americans to get vaccinated, especially as the U.S. prepares for an expected surge in Delta Covid infections in the fall.
On Monday, the U.S. reached Biden’s goal set in May to have 70% of U.S. adults with at least one shot of the vaccine, about one month behind the original July goal.
CDC indicates that the U.S. is reporting an average of approximately 600,000 vaccinations per day as of Sunday. This is far from the more than 3 million daily shots in mid-April, but up 14% from the week prior.
Last week, Biden announced that federal workers will be required to prove their Covid vaccination status or submit to safety protocols.
— CNBC’s Berkeley Lovelace Jr. and Jacob Pramuk contributed to this report
This story is developing. Please check back for updates.