CHICAGO (CBS) — What a difference two months make.

In mid-July, conventions and big events like the Chicago Auto Show returned to McCormick Place. We saw big crowds and few masks, and didn’t think much of it.

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But just afterward, the Delta variant of the coronavirus spread, and the world took a U-turn back to strict COVID protocols.

CBS 2’s Tim McNicholas took us back inside McCormick Place to see how a convention can be held despite a spike in cases.

The best brains and greatest gadgets in 3D printing all recently gathered at McCormick Place. But one of the most popular at the convention was a little simpler.

“Frankly, everyone’s brought their masks,” said Angie Szerlong.

The RAPID + TCT conference – one of the 3D printing industry’s largest conferences – was initially planned for April. They also planned from the beginning to spread things out more this year on the convention hall floor.

“We designed the floor plan quite differently this year with wider aisles,” Szerlong said.

The pandemic forced Szerlong and other organizers to push the event back to September. They didn’t know then that Chicago and the rest of the country would be grappling with the Delta variant.

“I would say that we’ve put every measure in place for health and safety, and we’ve allowed for things such as live-streaming for those that feel more comfortable watching remotely and being involved it,” Szerlong said.

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Organizers said the conference will bring about 3,500 people to McCormick Place over the course of the three-day event.

“People coming in from out of town,” said University of Illinois at Chicago epidemiologist Katrine Wallace. “Lots of people gathering indoors.”

Wallace recommends more safety measures for this event and others like it.

“It would be safer if they also had vaccine cards, and/or the negative COVID test,” she said.

McNicholas asked Szerlong if there were any such requirements at the convention.

“No, we’re following all CDC guidelines, local mandates; but we are currently no mandate for vaccines,” she said,

Exhibitors say the conference lets them show off their products in ways that a video cannot.

“We took the vaccines, and we put the mask on, and we do everything that we can in order to continue living with this,” said Shai Terem, chief executive officer of Markforged. “I don’t think it’s going away any time soon.”

But if only it would.

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The final day of that conference is Wednesday. Organizers say their attendance will end up about 15 percent less than pre-pandemic numbers.

Tim McNicholas