Senator Angus King, I-Maine, left, Senator Roger Wicker (R-MS)

Bill Clark / CQ-Roll Call, Inc. via Getty Images; Tom Williams Pool | Getty Images

Sens. Roger Wicker and Angus King, who are both vaccinated against the coronavirus, tested positive for Covid-19 on Thursday after symptoms appeared.

Wicker, a Republican from Mississippi, and King, an independent from Maine, are the latest in a line of prominent politicians who in the past few weeks have announced positive coronavirus tests despite being fully vaccinated. Others include Republican Senator Lindsey Graham of South Carolina and Governor Greg Abbott of Texas.

“Senator Wicker is fully vaccinated against COVID-19, is in good health and is being treated by his doctor in Tupelo,” Wicker communications director Phillip Waller said in a statement. The 70-year-old Wicker “is isolated and everyone with whom Senator Wicker has been in close contact recently has been informed.”

The Senate is on hiatus this week, and many of the Chamber’s members are in their home states either to prepare for the 2022 elections or to report to the district offices.

“Despite my best efforts when I had a mild fever yesterday, I took a test this morning at the suggestion of my doctor and it came back positive,” King, 77, said in a statement. “While I don’t feel great, I definitely feel a lot better than I would have without the vaccine.”

Senator Angus King (I-Maine) holds a chart as bipartisan Senate and House members gather to announce a framework for new coronavirus relief laws at a press conference on Capitol Hill on December 1, 2020.

Kevin Lemarque | Reuters

The positive tests from Wicker and King came as the Biden administration stepped up efforts to encourage Americans to get a booster vaccination starting next month, amid a growing pool of data showing that vaccine protection is wearing off over time.

Three of Washington’s top health experts on Wednesday gave more details on how immune system protection is wearing off over time.

It is now “very clear” that immunity decreases after the first two doses, and with the dominance of the Delta variant, “we see evidence of decreased protection against mild and moderate illness,” according to a statement signed by CDC Director Dr. Rochelle Walensky, Acting FDA Commissioner Dr. Janet Woodcock, the White House Senior Medical Advisor, Dr. Anthony Fauci, and other US health leaders.

New Covid-19 cases are occurring at the highest rates since winter as the delta variant of the coronavirus sweeps away US health experts showing that fully vaccinated people are still at risk.

More than 140,000 new cases and 822 deaths were reported in the United States on Monday, according to the Centers for Disease Control and Prevention. The number of new daily deaths has more than doubled since early August.

The situation in Florida and Texas is particularly dire as the case numbers in both states are breaking records and overwhelming hospital systems.