SPRINGFIELD, Ill. – Former Vice President Joe Biden won’t be campaigning at the Illinois State Fair due to an illness, state Democrats announced late Tuesday.

Biden had been scheduled to take part as a keynote speaker at Illinois State Fair Democrat Day Thursday to help bolster support for Democratic gubernatorial candidate J.B. Pritzker.

But Doug House, president of the Illinois Democratic County Chairs’ Association, said in a statement Tuesday night that Biden is “under doctor’s orders not to travel.”

Biden was scheduled to keynote the County Chairs’ Association brunch at a Springfield hotel. The brunch kicks off the day’s activities. The association on Wednesday morning announced South Bend, Indiana Mayor Pete Buttiglieg will replace Biden as the headliner.

UPDATE : Illness that nixed Biden’s Illinois visit ‘nothing serious,’ his office says

The State Journal-Register in Springfield reports the 2,500 tickets for hotel’s main ballroom had been sold to the Biden event. Demand for tickets had prompted use of a second room that holds 700 people.

“Everyone who knows Vice President Biden knows that he gives our party and our country his all, but unfortunately he is sick and is under doctor’s orders not to travel,” the statement said.

“The cancellation is of course disappointing, but it is clear that the circumstances are simply unavoidable. We all hope he gets well soon and I’m sure he’ll be back campaigning for Democrats in Illinois and across the country in no time,” House said.

House said Democrat Day activities will still go on, although Biden — named as a possible Democratic presidential contender — and his absence will be noticeable at Thursday’s events which were intended to provide a boost to Pritzker’s campaign.

Capitol Fax, the political blog, first reported the cancellation.