Updated

When it comes to preparing for a swine flu outbreak, the top concern for most U.S. business leaders is getting enough vaccine for their employees, according to a new survey.

The Business Roundtable found that most businesses have a plan to deal with the flu, but don't know how or when they will get enough doses of swine flu vaccine for their employees.

It will be months before businesses are given the new vaccine, if they get it at all. Health care agencies will be the first priority, with about 90,000 sites — mainly hospitals, clinics, doctors' offices, county health departments and pharmacies — expected to receive doses.

Business Roundtable President John Castellani said almost 90 percent of the industry group's members — including several Fortune 500 companies — had a plan to deal with flu season that they have updated since the swine flu appeared in April.

"Companies are on top of the situation," Castellani said Wednesday.

Business owners are not the only ones worried about the costs and other damage from a potential outbreak. Another report released Wednesday estimated that closing U.S. schools and day care centers because of swine flu could cost nearly $50 billion.

The Brookings Institution's Center on Social and Economic Dynamics estimated that the cost of closing all schools in the U.S. for four weeks would be between $10 billion to $47 billion. The Washington think tank called that a conservative estimate.

The government is urging schools to close only as a last resort. But as of Monday, there had been at least 187 school dismissals across the country affecting at least 79,678 students, the Education Department said.

Companies are waiting to see how big the economic impact will be, and how much extra sick time they might have to grant, Castellani said. That all depends on the severity of the flu.

About one-third of companies said they want more up-to-date information about the flu's severity, according to the Business Roundtable survey. The businesses were dissatisfied with the World Health Organization's flu pandemic warning system, which tells how far the flu is spreading rather than how sick it is making people.

Companies are stepping up their own efforts to communicate with employees, by e-mailing them updates on sick leave policies and referring them to sources where they can learn more about the flu, according to the survey.

About 225 million doses of the swine flu vaccine are expected to be doled out through this winter. The federal government is covering the cost of the vaccines and related supplies, according to the Centers for Disease Control and Prevention.