Ever wonder who came up with the concept of effective hand washing to help prevent the spread of germs? Bayer Corp. employees can tell you.

Workers at its U.S. headquarters in Robinson received a campus-wide e-mail last week on how Hungarian physician Ignatz Semmelweis, while working in a women's maternity hospital in the 1840s, discovered that by washing hands after each patient exam, doctors could reduce the number of infections contracted by their patients.

Bayer has been posting hand washing tips on its internal Web site at the start of flu season for years, but this recent missive was one of several flu prevention advisories Bayer sent out after a nationwide vaccine shortage forced it to cancel its annual flu shot clinics.

In the absence of flu shots, Bayer, Mellon Financial and other companies across the region and country are relying on internal communications to remind workers what their mom used to tell them as cold and flu season arrived: wash your hands frequently, cover your mouth and nose with a tissue when you cough or sneeze, and stay home if you are sick.

It may seem simple enough, but companies have a lot vested in making sure employees aren't bombarded with the flu bug. So much so that at some operations, Bayer has distributed flu prevention kits that include hand wipes, cough drops, vitamin C tablets and tea bags. The company also instructed the cleaning crew at one location to take extra steps to decontaminate door handles and to intensify bathroom cleaning.

The overall aim is to have fewer employees get sick so that business doesn't suffer. "If it's a routine flu season, hopefully [the flu] will have very little impact on productivity," said Donald Molenaar, Bayer's vice president of corporate medical services. "We've got our fingers crossed that this will not be a severe flu season and that if workers do get ill they will take steps to sequester themselves and not let it spread."

At Mellon's Downtown headquarters, about half of the typical 1,000 employees lined up for recent flu shots because the company was only able to obtain half as many vaccines as usual, said Lisa B. Peters, executive vice president and director of human resources. Mellon had asked employees, who pay for their own shots, to follow Centers for Disease Control and Prevention guidelines and only apply for the shots if they were high-risk.

"We're pretty proud of our employees," who received the vaccines on a first-come, first-served basis, Peters said. "There were no fisticuffs" over the limited number of shots.

Mellon also posted flu prevention tips on its employee Web site including advice to stay home when they are sick, stay in bed and drink plenty of fluids.

"We know with the flu, it's highly contagious and just has the effect of getting other people in the workplace sick," said Peters. "If employees are here and they're sick, they're not as productive. They need to be back here when they're well."

It is true that computer technology allows many Mellon employees to work from home, but Peters doesn't encourage telecommuting for those who are really ill. "If they're too sick to be at work, I don't expect them to log into their computer at home."

At the free flu shot clinic offered to employees the last four years, Downtown accounting firm Alpern Rosenthal usually inoculated about one-third of its 170 workers. So after it was forced to cancel this year's clinic, the firm published flu prevention tips on its internal news site.

More broadly, Alpern Rosenthal is trying to encourage employee wellness and productivity through programs such as an on-site health fair, at which employees can get free cholesterol and blood screenings, and a Weight Watchers program held in its offices at lunch time.

"I do think [the flu vaccine shortage] raised awareness [that being healthy] reduces sick time and that's important to us and to our employees who might spread illnesses to their families," said Elisabeth Leach, a firm principal.

Maybe employers don't have to worry about the flu as much as they think they do -- there likely are other reasons to worry.

A new survey on unscheduled absences reports that 62 percent of workers who call off aren't even sick. They're skipping work because of stress, family issues and other personal reasons, said CCH Inc., a human resources consulting firm that compiled data from 300-plus companies nationwide.

The good news: While the rate at which workers are calling off is the highest in five years, productivity in the United States is at an all-time high, CCH said.