NEW YORK (CNN/Money) - A flu season made worse by a shortage of flu vaccine could cost the U.S. economy about $20 billion in health care costs and employee absences, according to a published report Monday.

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The Wall Street Journal quotes David Cutler, a professor of economics at Harvard University, as saying the $20 billion estimate is up from the $13 billion to $15 billion in direct and indirect costs of a typical flu season. That would represent a rise in costs of between 33 to nearly 50 percent.

The U.S. is facing a shortage of flu vaccine after Chiron Corp. (Research), which the U.S. government had counted on for about half the nation's supply, had its entire stock of the vaccine pulled because of problems discovered by British health authorities inspecting the Liverpool, England, plant that makes the vaccine.

U.S. public health authorities are urging that only those most at risk of health problems from the flu get flu shots this year. But many of those in the at-risk population, including the chronically ill, the elderly and infants age 2 and younger, are not in the work force.

Thus, many of those in the work force who normally get a flu shot will go into this year's flu season without their normal vaccine.

The Journal reports a recent study by ComPsych Corp., a Chicago human resources service firm, found 40 percent of people who don't get shots miss some time at work because of the flu, compared with less than 20 percent of people who receive flu shots.

"If we have a normal flu season and there are no shots available we're going to have a significant number of people miss work," CompPsych CEO Richard Chaifetz told the paper.

The paper reports that about 60 percent of employers had planned to offer flu vaccinations to their employees this year in an effort to cut illness and absenteeism among their work force. But the paper reported nearly all of those company programs are being put on hold or scrapped due to the vaccine shortage and the focus on using available vaccine on high-risk individuals.

Companies will focus on education and such measures as hand-sanitizer units instead of vaccine to do what they can to combat this flu season, the Journal said.