Grab Your Lanyard. Trade Shows Are Plotting a Comeback.

Masks, temperature checks and Covid-19 tests were mandatory. Booths were spaced out, aisles had no carpets and floor markings reminding attendees to keep their distance were ubiquitous. Hand sanitizers were swag mainstays. “No hugs or handshakes this year,” an event website read.

The roughly $11 billion U.S. trade-show and exhibition industry is slowly coming back to life after a largely lost year due to coronavirus. A full recovery isn’t expected for about two years, industry executives say, and many questions now face organizers and the businesses that rely on lanyard-clad masses: How quickly can shows, which require months of planning, come back on the calendar? Are attendees ready to crowd into expo halls and hotel bars with strangers again? And, after a year of remote networking, do they feel they need to?

Some of the biggest shows are planning to resume in person, with options for tuning in virtually. Mobile World Congress, which hosted more than 109,000 attendees in Barcelona in 2019, will return with a hybrid option in June after scrapping the event in 2020. CES, the world’s largest tech show, went virtual this year and expects to return with a hybrid option in Las Vegas in January 2022.

In the U.S., the federal Centers for Disease Control and Prevention currently discourages large events and gatherings, citing “extremely high” cases of Covid-19 across the country. If the gathering involves attendees from outside the local area, the agency advises event staff to provide information about local Covid-19 levels so attendees could make informed decisions about their participation.

The joint gathering of apparel shows in Orlando was a “pilot” to test the effectiveness of precautionary measures at a smaller scale, said Douglas Emslie, group chief executive of Offprice organizer Tarsus Group PLC.

“This was not an event where we made any profit at all,” Mr. Emslie said. “This was an investment for the industry to prove that we can run these events.”

Eighteen attendees who took an on-site Covid-19 test outside of the exhibition hall returned a positive result, and those who did immediately left the venue, organizers said. They said they haven’t received reports of positive cases after the event.

Both attendees and organizers understood the risks of an in-person event, Mr. Emslie said.

“The intention was never to create a bubble that was there consistently for the three days,” Mr. Emslie said. “This is about risk management, and it was never going to be 100%, and we never presented it to our attendees that it was going to be 100%.”

One attendee, Steven Gasparovic for B&S Activewear LLC, said going to the trade show was a quick way for the firm to strike 15 sales in a three-day period—even if it required spraying sanitizer on every piece of fabric after a visitor touched it.

“The cost of sending out as many samples as you get to put in front of a customer is astronomical, comparatively speaking to being in a venue where they’re coming to you,” said Mr. Gasparovic, the clothing wholesaler’s director of U.S. operations. He said he felt reassured knowing that all attendees had been tested before the event. The venue didn’t feel crowded, he said, and he witnessed exhibition staff patrolling to remind attendees to properly wear their masks.

The organizers say they hope to return to Las Vegas this year. An expert group hired by a trade association for the events industry is evaluating the apparel shows’ health and safety measures for a report that it plans to submit to government officials including the Nevada governor.

Trade shows and conferences give attendees and vendors the chance to rub elbows with far-flung clients and prospects, but that’s also what makes restarting them risky. In February 2020, before scientists had devoted significant resources to understanding how the virus could be transmitted, an international meeting of

Biogen Inc.

managers held in Boston spread Covid-19 to thousands of people as far away as Michigan, Virginia and Australia, according to researchers who conducted a genetic analysis.

But even an additional year’s worth of knowledge about the virus is no guarantee of safety. Abundance 360, an in-person and virtual gathering of executives held this January in Culver City, Calif., led to 24 positive cases, or roughly a quarter of people at the event, including participants and staff, according to Peter Diamandis, who led the conference.

Mr. Diamandis, who was among those who tested positive, wrote in a blog post that he sought to create an “immunity bubble” by requiring attendees to take Covid-19 tests three days before the event and upon arrival. Organizers then tested attendees every morning during the four-day event, he said. Los Angeles County currently limits private gatherings to three households and up to 15 people.

“I thought five physicians and 452 tests and my entire safety team could maintain safety,” said Mr. Diamandis, the founder of the nonprofit XPrize Foundation, which gives out prizes for innovative projects. “I was wrong.”

Hospitality-industry executives say business travel could pick up in the second half of 2021, but trade shows aren’t expected to rebound to pre-Covid levels until about 2023. That’s partly because restrictions on international travel remain in place, said Cathy Breden, chief operating officer of the industry group International Association of Exhibitions and Events.

Andrew Dias III, who has worked as an optician in Washington, D.C., has attended a gathering of eye-care providers and optical retailers called Vision Expo nearly every year for the past decade or so, until the 2020 events were canceled. This year, he said he’s likely to attend virtually. Mr. Dias said he’s unsure whether the country’s pandemic trajectory will have recovered enough by summer.

“They’re jumping the gun a little bit,” Mr. Dias said.

Vision Expo, scheduled for June 2 to 5 in Orlando’s Orange County Convention Center, moved from New York City’s Jacob K. Javits Convention Center, now a Covid-19 vaccination center. Registration will open later this month, and organizers said the venue is capable of accommodating the event’s pre-Covid capacity of nearly 15,000 people.

“We take our responsibility to our attendees and the entire industry very seriously and would not host this event if we were not confident that we could provide a good opportunity for the community to come together to do business while following every possible guideline to ensure their safety,” said Ashley Mills, CEO of the Vision Council, which co-owns the Vision Expo.

Florida, which has remained largely open since last year, is playing host to many relocated events. The Orange County Convention Center has hosted about 60 events since lockdowns started in March 2020, and about 15 events, past and upcoming, have relocated there from other states, Executive Director Mark Tester said. The convention center is maintaining strict cleaning and social-distancing rules, and the venue has spent more than $300,000 to retrofit its facilities, a spokeswoman said.

Still, more than 90% of the center’s scheduled events have been canceled or rescheduled this year and last, Mr. Tester said. The business-to-business exhibition industry added about $21 billion to the U.S. economy in 2020, an $84 billion decline from 2019 due to the pandemic, according to the Center for Exhibition Industry Research.

Some professionals may be ready to hit the road again, but corporate compliance departments may hold back some travels to trade shows.

Facebook Inc.,

Sony Corp.

and

Ericsson

AB are a few companies that have said they won’t be sending representatives to this year’s Mobile World Congress. And government workers may face the same restrictions.

FDR Training, a conference planned for August in Orlando for some 1,500 federal professionals, will depend on the U.S. government’s travel policy for its employees, said Kenneth Kahn, president of organizer LRP Media Group.

The Office of Management and Budget, in a Jan. 24 memo, advised that domestic travel by federal employees should be limited to trips the government deems “mission critical.” President Biden on Thursday pressed states to widen Covid-19 vaccine eligibility to all U.S. adults by May 1, calling for an all-hands effort to defeat the coronavirus to set the stage for small gatherings during the Independence Day weekend.

“Unless the federal government lifts their current travel [restrictions], that conference may be problematic,” Mr. Kahn said.

Write to Dave Sebastian at dave.sebastian@wsj.com