Illinois Senate President Don Harmon has contracted a breakthrough case of the coronavirus after being vaccinated this spring, a spokeswoman said Monday.

       Harmon, an Oak Park Democrat, began experiencing mild symptoms late last week and quarantined while awaiting test results, according to a statement from spokeswoman Liz Mitchell.

       Contact tracing efforts began when the positive results were received. Harmon does not know where he might have contracted the virus, Mitchell said.

       “I’m even more grateful to be vaccinated, given how mild my symptoms have been,” Harmon said in a statement. “I encourage everyone to get vaccinated and also to not let their guard down as we try to get back to normal.”

       Illinois Senate President Don Harmon speaks before Gov. J.B. Pritzker signed HB 3653, a sweeping criminal justice and police reform bill, on Monday, Feb. 22, 2021 at Chicago State University. (Brian Cassella / Chicago Tribune)

       Harmon has canceled plans to attend the Illinois Democratic County Chairs’ Association breakfast Wednesday morning ahead of Governor’s Day at the Illinois State Fair, a spokesman for his political operation said.

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       Harmon’s cases wouldn’t be counted among the official data on breakthrough coronavirus infections because state and federal health officials only track cases among fully vaccinated people if they result in hospitalization or death.

       As of Wednesday, the most recent data available, there have been 899 hospitalizations and 189 deaths among fully vaccinated people in Illinois since the beginning of the year, according to the state Department of Public Health. Those deaths account for about 2.7% of all coronavirus-related deaths this year.

       Harmon is the second top legislative leaders to publicly announce a COVID-19 diagnosis. Speaker Emanuel “Chris” Welch, a Hillside Democrat, tested positive last fall before he was elected in January to lead the Illinois House.

       Along with Harmon and Welch, the legislature’s top Republicans, Senate GOP leader Dan McConchie of Hawthorn Woods and House GOP leader Jim Durkin of Western Springs, have publicly said that they are vaccinated.

       dpetrella@chicagotribune.com

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