Tavon Stokes, 22, is seldom sick and keeps in shape by running and walking. He figures he has no need to see a doctor.

So even though the full-time sales clerk from Baltimore could get health insurance from his employer, RadioShack, Stokes figures he can find far better ways to spend his cash.

Health problems "aren't coming up yet, so it's not much of a priority," he said.

In the debate over health care reform, Stokes and his peers are known as "invincibles," strong and healthy young adults who have no experience with wallet-crippling illness and feel they have no need for coverage.

They're also the most likely to be affected by the reform effort that President Barack Obama insisted in Wednesday's prime-time address to Congress is crucial to the future of the economy.

Adults ages 18 to 34 comprise more than half of the nation's uninsured. Under the various plans before Congress, they would be required to get health insurance or face penalties if they refuse.

While young adults supported Obama in huge numbers during last year's election, they have been relatively quiet about his quest for health reform despite the stakes involved. Noisy town hall meetings last month drew older crowds. Polls show that young adults are ambivalent about the need for reform and are generally paying less attention than their parents and grandparents. It is unclear whether Obama's address swayed many of them.

"Many folks in their 20s are pretty apathetic about health care in general, because they think, 'I'm not going to get sick,' " said Matthew Celentano, deputy director of the nonprofit Maryland Health Care for All.

That's dangerous, he said, because more than half of bankruptcies are health care- related. "You have a 23-year-old who gets in a car crash and is suddenly looking at $500,000 in medical bills. It happens all the time, but they don't think in those terms. They're really a forgotten sector."

The disconnect worried Jovany Andrade enough that he helped organize a health care forum at the University of Maryland, Baltimore last week. The 30-year-old pharmacy and public health student recalled his own indifference to health issues during his undergraduate years.

"I think we're going to look back in 10 years and realize this was a historic time," he said.

Insurance companies are hungry to sign up invincibles: Premiums of young people who don't need much care mean money that can be spent on those who do.

While some analysts say mandated insurance would place financial burdens on the young and healthy, others say they would be helped by proposals to subsidize those with lower incomes and to allow them to be covered longer under their parents' health plans.

Stokes, for one, would not be upset if Obama's plan mandated that he buy health insurance. He knows he needs to grow up a bit and take responsibility for himself - and being insured would be a step in that direction.

"I've known that's something I need to take seriously, so I'm glad he's enforcing it," Stokes said. "I wouldn't mind."

However, many young adults say they have gone uninsured or minimally insured out of necessity, not choice. Many entry-level jobs do not offer insurance, and private plans are expensive. Presented with a choice between crippling their budgets and betting that they will remain healthy, young adults reluctantly go without insurance.

More than one in four adults between ages 18 and 34 were without health insurance in 2008, according to a census report released Thursday. They account for 55.1 percent of uninsured Americans, and the percentage is growing, up from 53.8 percent a year earlier.

When Chaundra Scott graduated from college, her mother's insurance dropped her and she could not afford COBRA coverage. The Hanover native found a social work job, but it offered no health benefits. So for three years, she went uninsured.

Scott suffers from asthma and eczema and said that while uninsured, she had to go to the emergency room four or five times a year for treatment.

"The debt piled up from me not paying my bills," she said.