When Kim Williams and millions of other older Americans lost their jobs early in the coronavirus pandemic, economists wondered how many would ever work again — and how that loss would weigh on the economy for years to come.

Ms. Williams, now 62, wondered, too, especially when she struggled for months to find work. But in January, she started a new job at an AAA office near her home in Waterbury, Conn.

“I’m too young to retire, so I had to go back,” she said.

Whether by choice or financial necessity, millions of older Americans have made the same move in recent months. Nearly 64 percent of adults between the ages of 55 and 64 were working in April, essentially the same rate as in February 2020. That’s a more complete recovery than among most younger age groups.

The rapid rebound has surprised many economists, who thought that fear of the virus — which is far deadlier for older people — would contribute to a wave of early retirements, especially because many people’s savings had been fattened by years of market gains. But there is increasing evidence that the early-retirement narrative was overblown.

“The bottom line is that older workers have gone back to work,” said Alicia Munnell, director of the Center for Retirement Research at Boston College.

For many people, retiring early was never an option. Ms. Williams spent more than 25 years in manufacturing, working for a Hershey’s plant making Almond Joy and Mounds bars. The job paid reasonably well, and offered a retirement plan and other benefits. But in 2007, Hershey’s closed the factory, moving production partly to Mexico.

Ms. Williams, then in her 40s, went back to school, earning an associate degree in hospitality and eventually finding a job as a supervisor at a local hotel. But the position paid significantly less than her factory job, and she drew down her retirement savings to cover medical expenses and other bills. When she was laid off again in June 2020, just a few weeks after her 60th birthday, Ms. Williams had little in savings.

Ms. Williams tried to change careers again, this time going back to school to train as a medical secretary. But she has been unable to find work in her new field. In January, with her savings gone, she took a job at AAA for $16.50 an hour, $2 an hour less than she earned at the factory in 2007, before accounting for inflation. She says she will have to work at least until she can start drawing her full Social Security benefits at age 67.

“If I could’ve left at 62, I would’ve left at 62, but I can’t,” she said. “Not all of us made that money where I could move down to Florida and get a $400,000 house.”

The fastest inflation in decades has added to the pressure on people of all ages to return to work. More recently, so has the turmoil in financial markets, which has taken a bite out of retirement savings.

But even some people who could retire are choosing to return to work as the pandemic ebbs.

When the Long Island fitness studio where she worked as a spinning instructor shut down early in the pandemic, Jackie Anscher lost both a job and a part of her identity. In an interview with The New York Times that summer, she described what seemed at the time like an abrupt end to her career as “a forced retirement.”

But after spending the beginning of the pandemic reorganizing her life and re-evaluating her priorities, Ms. Anscher, 60, has begun teaching spin classes again as a substitute instructor at a local gym, and she is looking for a more regular gig. Her husband is already retired — “he’s been waiting for me to go fishing,” she said — and the couple could afford for her to stop working. But she isn’t ready to hang up her cycling shoes.

“I liked what I had. I loved who I was in front of the room,” she said. “It’s about my mental health. For me, it’s about preserving me.”

Older workers weren’t any more likely than younger workers to leave the labor force early in the pandemic. But economists had reason to think they might be slower to return. Unemployed workers in their 50s and 60s typically have a harder time finding jobs than their younger counterparts, because of ageism and other factors. And unlike after the 2008-9 recession, when depressed housing prices and high debt levels left many people with little choice but to keep working, in this crisis prices of both homes and financial assets kept rising, providing a financial cushion to some people nearing retirement age.

The share of Americans reporting that they were retired did rise sharply in the spring of 2020. But retirement is not an irreversible decision. And research from the Federal Reserve Bank of Kansas City has found that at the pandemic’s onset, there was a steep drop in the number of people leaving retirement to return to work, attributable at least partly to fear of the virus and a lack of job opportunities, swelling the ranks of the retired.

As the economy has reopened and the public health situation has improved, these “unretirements” have rebounded and have recently returned roughly to their prepandemic rate, according to an analysis of government data by Nick Bunker of the Indeed Hiring Lab.

The return of older workers has been concentrated among those in their late 50s and early 60s, people who were still several years or more away from retirement when the pandemic began. The employment rate among those 65 and older fell more sharply and has been much slower to recover. That suggests that the pandemic might have led some people who were already closer to retirement to accelerate those plans, and that the greater health risks they faced may have made them less likely to return to work while the virus continues to circulate.

Still, the return of early retirees to the labor force is a reminder that rising wages and abundant job opportunities can draw in workers who might otherwise remain on the sidelines, Mr. Bunker said. The labor force shrank during the last recession, too, and some economists were quick to declare that workers were gone for good. But many people eventually came back during the strong job market that preceded the pandemic: It provided opportunities to people with disabilities and criminal records, to people with little formal education and to people who had taken time away from work to raise children or to care for ailing parents.

That pattern may be repeating itself, but on a much more compressed timeline.

“Don’t underestimate labor supply,” Mr. Bunker said. “Don’t count out the possibility that people want and need work. It has happened much more quickly than what we saw after the global financial crisis, but the broad principle is the same.”

When Tad Greener lost his job managing utilities for a Utah university in late 2019, he wasn’t worried at first about finding a new one — the unemployment rate, after all, was near a 50-year low. But Mr. Greener had hardly begun his search when the pandemic hit and the bottom fell out of the economy. Suddenly, he was 60 years old, unemployed and facing the worst labor market in nearly a century.

Mr. Greener eased up on his job search during the first phase of the pandemic, in part because of some health issues unrelated to the coronavirus. By spring of 2021, he was ready to work again, but he had little luck applying for jobs. He thinks many prospective employers were turned off by the combination of his age and his time out of the work force.

“It’s a daunting task to be 62 years old, to be unemployed for over a year and to try and find work,” Mr. Greener said. “There were times where I didn’t think I was ever going to be able to go back to work.”

As the economy reopened, however, many businesses struggled to hire enough workers to meet the surge in demand. That prompted employers to consider candidates they might otherwise have dismissed, or to look for ways to attract people who could work but weren’t looking.

In Mr. Greener’s case, he learned about a new “returnship” program from the State of Utah that was meant to help people who had been out of the labor force get back to work. Last fall, he was accepted into the program, landing a part-time job in the state Office of Energy Development, which quickly turned into a permanent, full-time job. Now that he is back at work, Mr. Greener says he plans to stay until he is 67, or perhaps longer if he stays healthy.

“Every day I hear about how there aren’t enough workers available,” Mr. Greener said. “There are a lot of older workers that are being written off, or at least finding it much more difficult to get back into the workplace, who have a lot of years and things to offer.”