In the latest Illinois Department of Public Health count released Tuesday, the state’s southern region reported that, overnight Monday, its hospitals had no available ICU beds in an area that includes roughly 400,000 people. As of Tuesday morning, 19 hospitals in that region still had zero open ICU beds, said Arien Herrmann, regional hospital coordinating center manager for the area.

Herrmann and public health advocates say it’s clear that the lack of ICU beds in the region is due to the area’s low vaccination rates. As of Tuesday, the region’s rate was just 38% of residents fully vaccinated, according to a Tribune analysis. That compares with the five regions in the Chicago area, in which all are above 52% and one — covering DuPage and Kane counties — tops 60%.

“We have the lowest vaccination rate in the state,” Herrmann said. “It’s that simple. I really think the data speaks for itself.”

The lack of ICU beds in southern Illinois this week epitomizes what has been one of the worst fears of state leaders throughout the pandemic: that hospitals could get overrun. That’s one way state leaders historically have rationalized shutdowns and mask mandates — arguing it’s about limiting a virus’s spread so everyone’s collective health care system doesn’t collapse.