U.S. Sen. John Hickenlooper tested positive for COVID-19 Thursday after experiencing what the Colorado Democrat described as mild symptoms.

Hickenlooper, 69, was fully vaccinated, he said in a statement that urged others to “get the shot today.”

“After experiencing mild symptoms, I tested positive for a breakthrough case of COVID-19. I’m feeling much better and will continue to isolate at the direction of the Congressional Attending Physician,” Hickenlooper said in a statement.

“I’m grateful for the vaccine (and the scientists behind it) for limiting my symptoms and allowing us to continue our work for Colorado. If you haven’t been vaccinated, don’t wait for the virus – get the shot today, and a booster when it’s available too!”

Hickenlooper was the third senator to announce Thursday that he’s tested positive for the coronavirus. Hours earlier, U.S. Sens. Roger Wicker, a Mississippi Republican, and  U.S. Sen. Angus King, a Maine independent, who are both fully vaccinated, said they had what are referred to as breakthrough cases.

The announcement comes as Colorado has been experiencing a surge in cases that authorities attribute to the rapidly spreading delta variant, which has led to spikes in hospitalization across the country. On  Wednesday, Colorado reported more than 2,000 new COVID-19 cases, the most in a single day since late April, though health officials said the state is in a better position than other states.