A little over a year ago, Chanee McLaurin was a few weeks into a new job selling insurance when she began to hear coughing in her office.

Co-workers, one after another, stopped showing up. Then she overheard a colleague whispering into her phone that she had been diagnosed with flu-like symptoms.

“I was like, ‘You know what? I’m going to go home. And I’m probably not going to come back,’” said Ms. McLaurin, who is 29 and lives in a suburb of Dallas.

When her employer, after letting staff work from home, called them back to the office in early May, Ms. McLaurin didn’t go. Although she wasn’t aware of any outbreak at her office, her job involved going door to door at businesses, and she feared what would happen if she caught Covid-19 and grew too ill to take care of her two-year-old daughter or infected her wife, an essential worker with a warehousing job.

A year after the pandemic burst onto the U.S. economy, 8.4 million fewer Americans hold jobs. There are many reasons, but one of the most important and least appreciated is the one that keeps Ms. McLaurin at home: fear. A U.S. Census survey conducted in the second half of March found that about 4.2 million adults aren’t working because they are afraid of getting or spreading the coronavirus.