SAN FRANCISCO – McAfee Inc. is in the business of preventing computer viruses. But the flu vaccine shortage has forced the California company and thousands of other firms around the country to scramble for alternative methods to protect their employees against people-borne viruses.

Among other things, those firms are ordering more hand-sanitizer dispensers, extolling the virtues of green tea extract and holding wellness meetings with employees.

When British regulators on Oct. 5 suddenly shut down the Chiron Corp. factory in Liverpool that supplied half of the U.S. supply of influenza vaccine, it also scrubbed plans by hundreds of thousands of companies to administer flu shots to employees.

About 60 percent of the companies that are members of the Society for Human Resource Management planned to offer onsite flu vaccines to employees this year. But the flu shot shortage curtailed those plans, said Jen Jorgensen, spokeswoman for the 190,000-member organization.

As a protective measure, McAfee has ordered more germ-killing hand-sanitizer dispensers and lotion to augment regular bathroom soap dispensers at its offices in Santa Clara and Sunnyvale. The company also had building engineers increase water pressure so that warm water, which cleans hands more thoroughly than cold water, flows more quickly into bathroom taps.

Laser instruments-maker Coherent Inc., which had to cancel its annual flu vaccine days, is spending about $1,500 to install new automatic hand sanitizers made by a Northern California firm in high-traffic areas like employee break rooms, gyms, copy rooms and mailrooms in facilities in Santa Clara and Auburn.

“The way we look at it, it’s going to save us in the long run from having employees going out ill,” Coherent spokesman Peter Schuman said. “All it takes is one person to start spreading it, and all of a sudden your whole department is out ill.”

Jorgensen of the Society for Human Resource Management said many employers are stepping up flu prevention education, such as counseling employees against coming to work when they are sick just because they “feel they need to suck it up and come into the office through rain, sleet, snow or flu. It’s the fastest way to spread it to the rest of the workplace.”

Some employers like the University of California’s president’s office in Oakland are still scheduling flu shots, but only for employees who signed affidavits stating they are part of a group considered at greater risk of serious flu complications, such as people 65 and older and pregnant women.

Other firms are trying more unusual methods. For example, TW Creative Communications of Tampa, Fla., is providing employees with a concentrated green tea extract from Pure Inventions LLC of New Jersey to bolster their immune systems.

“The benefits of the drink cannot be overlooked at any time, but especially during this upcoming flu season,” said TW Creative spokeswoman Natalie Cacciatore.

Coherent Inc. is installing automatic hand-sanitizer dispensers made by Best Sanitizers Inc. of Penn Valley to encourage employees to keep their hands clean at all times.

“Some people are good hand washers, and some are not,” said Best Sanitizers President Hillard Witt. “Everyone’s using the same copiers and fax machines. We’re constantly shaking hands, using the same restrooms.”

Sue Felt, associate epidemiologist at San Francisco General Hospital, said the hospital has canceled its annual immunization clinic for workers and sent letters urging them to take precautions with their patients, including giving outpatients with influenza-like symptoms a surgical mask as well as keeping them separated from other patients as much as possible.

The workers themselves have been asked to continue exercising proper hygiene, such as covering their mouths when they sneeze and washing their hands frequently.