The shortage of flu vaccine this fall poses serious challenges for employers concerned about productivity, and for low-wage workers who don't have paid sick leave and can't afford to miss a day.

Federal Centers for Disease Control and Prevention studies show that immunized workers have 44 percent fewer doctor visits during the flu season. That's one reason, according to the Society for Human Resource Management, why 60 percent of business organizations usually offer flu shots to their workers.

But with half the expected supply missing this fall, government health officials are telling workers they should stay home if they get the flu so the illness doesn't spread.

That means a change of plans for many companies. McLean mortgage buyer Freddie Mac told workers in a memo Tuesday that, in place of the vaccine, they should wash their hands, get plenty of sleep and eat well to help ward off the disease.

Booz Allen Hamilton Inc. had to call off planned shots for employees too. "Fortunately, we're a youthful and healthful workplace," said spokesman George Farrar.

The outlook isn't as hopeful for the half of the American workforce that doesn't have paid sick leave, and thus has to work or lose money.

Some face starker choices. Connie Smith says her manager gave her an ultimatum when she came down with the flu last January: Come to work sick or don't come back. So Smith, a store manager at a Popeyes in Milwaukee, worked her way through the 6 p.m. to 4 a.m. shift, coughing all over the crispy fried chicken, she recalls.

"She told me she didn't have nobody to replace me, and if I took the day off, I didn't have a job," Smith said. A doctor's note saying that she needed to take time off didn't matter, Smith said. "She still didn't let me take those days off. I was sneezing and vomiting."

John Brodersen, owner of the Milwaukee Popeyes, said, "The manager must have made a mistake" in Smith's case. "We don't pay anybody for sick days," he said. "But on the other hand, we don't require people to work if they are sick. That's our policy."

The Family and Medical Leave Act, which covers about 70 percent of the workforce, mandates that workers at companies with 50 or more employees get 12 weeks of unpaid leave per year.

Linda Meric, director of 9to5, National Association of Working Women, said that because of the gap in benefits, her group is supporting a proposal in Congress that would provide seven days of paid sick leave to every American worker.

The United States lags far behind most countries when it comes to time off for employees, be it sick leave, maternity leave, or absence to take care of a sick relative.

A study released this summer by Harvard University's Project on Global Working Families reported that 139 other countries provide paid leave for short- or long-term illnesses. And 117 of those nations guarantee workers a week or more of paid sick days per year. Meanwhile, at least 37 countries have policies guaranteeing parents some type of paid leave when their children are ill. The United States doesn't.

"In a state of affairs where the U.S. does not give sick leave to half of Americans, most of those workers feel they can not stay home. So without a doubt, we are spreading influenza and other illness," said Jody Heymann, associate professor at the Harvard School of Public Health, an author of the study. "What we should be doing on all fronts is fighting with the right and left hand, both with vaccines and preventing exposure by helping people stay home so they don't infect others. We do not have that now."

Debra L. Ness, president of the National Partnership for Women & Families, formerly the Women's Legal Defense Fund, argued that not providing paid days off to workers who should stay home with the flu is more expensive for companies. "If you manage to get yourself to work, then you're truly putting other people at risk of getting the flu. Then you start running into additional costs for employers who are going to end up with more sickness in their workforce," she said.

Business groups oppose the idea of requiring paid sick leave, saying it would cost companies too much money.

"We'd likely oppose the bill because it sets a precedent for mandatory paid leave, which will only be expanded," said Randel Johnson, U.S. Chamber of Commerce vice president of labor. "There already is a requirement in law that requires 12 weeks of unpaid leave. It would be a detriment for some businesses because some can afford paid leave and some can't."

Brian McDonough, the general manager of Contact One, a call center in Lakewood, Colo., doesn't offer paid sick leave to his employees. "We are a call center who answers calls on a 24/7 basis. Right now, it's every person for themselves," McDonough said. If the flu hits the 30 employees at his business, the company will "just juggle schedules and probably have to go into an overtime situation for those employees" who are not ill.

McDonough tells workers not to come in if they are sick. But he expects them to choose sick days wisely. "My position is when you're sick, you're sick. And when you're not, you come to work. And when your sickness is at such a chronic state that it affects the balance of the company, then something has to be done," he said.

Even companies that provide paid sick days find it hard to tell employees to just stay home.

"You take a day off and you're the worst employee in the world," said Roslyn Stone, chairwoman of the Centers for Disease Control and Prevention's workplace flu prevention group, and chief operating officer of Corporate Wellness Inc., a company that provides a medical department for midsize companies. Flu season coincides with retail's busiest season, the closing of books for most small and large businesses, and private parties in the restaurant business.

Her company was due to provide flu shots to about 1,000 corporate locations and "tens of thousands" of employees this year. But the company is waiting on distribution instructions from the government, and already had to relinquish some vaccines for high-risk organizations, like hospitals, she said.

Stone is concerned that workers will continue to come to work because they can't say no to a boss who asks them to come in, particularly in a busy season for businesses.

John Challenger, head of outplacement firm Challenger, Gray & Christmas Inc., said that businesses suffer productivity losses if employees come to work sick. Not only is the productivity of those workers quashed, but other employees are then vulnerable to illness. "Employees who come to work but are mostly unproductive due to poor health . . . can really damage a company's bottom line," he said.

Marty Cohen leads the line at the Greenbelt Road Safeway for a flu shot.