David Gibbons is seeing something in and around the Boston Convention and Exhibition Center that he hasn’t seen in more than 16 months: conventioneers.

The conventions and meetings industry was one of the first to close when COVID-19 hit, and it has been one of the last to return. But that long-awaited reopening is finally here, with the annual meeting of the Heart Rhythm Society, the first true business convention Boston has seen since the pandemic began.

“A lot of business needs to be in person,” said Gibbons, executive director of the Massachusetts Convention Center Authority. “The impact of a live show is that unexpected interaction: running into an old colleague, meeting new people. . . . You can’t program the unexpected over the Internet.”

The event this week drew about 4,000 cardiologists and others in the field to the massive BCEC complex in South Boston, event organizers said, with at least 1,000 more tuning in remotely via livestreams. The in-person event, held from Wednesday through Saturday, provides a mix of continuing education and networking, as well as technology updates from medical device companies in the exhibit hall.

It had been scheduled for May, but organizers decided to postpone with the hope that COVID-19 restrictions and case counts would ease from spring levels. The group’s 2020 annual meeting, planned for San Diego, was a completely virtual event. Fred Kusumoto, president of the society’s board of trustees, said the pandemic prompted the group to accelerate some long-discussed technical changes to allow for more remote participation. But he’s also pleased to reunite with colleagues in person again.

“Zoom is great for broadening and developing really wide connections, but not really deep connections,” said Kusumoto, an electrophysiologist at the Mayo Clinic’s campus in Jacksonville, Fla. “That is what’s wonderful about an in-person meeting that allows that type of interaction.”

The group handed out three types of lanyards to attendees, depending on their comfort level with COVID-19 precautions. Green lanyards mean any greeting is fine. Yellow lanyards indicate they’d prefer an elbow bump over a hug. Red means keep your distance. Some wore masks while many others did not. (People working the convention, though, were asked to mask up.) Chairs were set up with spaces to separate them, and panelists didn’t share microphones.

“It’s important for us to be together, but it’s at least as important for us to be together safely,” said Patricia Blake, the society’s chief executive.

The city’s hotel industry has been patiently waiting for events of this size to return, said Sebastian Colella, vice president at Pinnacle Advisory Group. An estimated 17,000 room nights were booked for this conference alone, he said. This comes as the sector is springing back to life: Boston’s hotels saw sizable growth in business in July compared to June, he said, driven primarily by strong leisure demand, with corporate travel also starting to rebound.

The BCEC and its sister facility in the Back Bay, the Hynes Convention Center, have about two dozen conferences, conventions, and other major events on the calendar for the rest of the year, each expected to draw thousands. Those include a few consumer-oriented shows with big crowds planned, including Fan Expo Boston in September, the Boston Marathon Expo in October, and the Snowbound Festival in November.

For much of the pandemic, the two convention centers were largely repurposed for other uses, including a makeshift hospital at the BCEC and a giant vaccination clinic at the Hynes. Revenue at the convention center authority fell sharply, approaching $16 million in the 12 months that ended in June — with nearly half coming from the Boston Common Garage — down from $57 million the prior fiscal year. For the 12-month period that began July 1, the authority expects $41 million in revenue and $68 million in expenses and will cover the difference by drawing from the state’s convention center fund, which is subsidized by tourism taxes.

“The next six months are certainly going to be unique,” Gibbons said. “Then things will settle in.”

One wild card, though, could be the rise of the ultra-contagious Delta variant, which prompted the Centers for Disease Control and Prevention on Tuesday to recommend that masks be worn in indoor public spaces in many parts of the country, including Suffolk County.

Gibbons said the MCCA has not yet had any requests for rescheduling or cancellations related to the emergence of the Delta variant. But he acknowledged the events of the past week could result in a “stutter step” for his industry’s recovery.

“Every day is different,” Gibbons said. “This is today’s reality. We’ll see next week.”