The U.S. Senate on Wednesday unanimously approved legislation to encourage drug and vaccine makers to develop countermeasures against a potentially devastating bioterror attack.

The $5.6 billion 10-year Project BioShield program, approved 99-0, creates incentives for research and basically guarantees a market for treatments, antidotes and vaccines that would otherwise not find a viable commercial niche.

The government will purchase and stockpile vaccines or treatments for potential bioterror agents such as smallpox, anthrax, botulism and ebola. The bill also will encourage more research in both the public and private sectors.

The legislation also allows the government to make experimental treatments available in an emergency, even if they have not completed the usual Food and Drug Administration approval process.

The U.S. House of Representatives passed similar legislation last year, and lawmakers said they expected to work out minor differences quickly so it can be signed into law. President Bush called on Congress in 2003 to create Project Bioshield.

Senate action caused several biotech companies stocks to rise. Among the companies analysts have cited as potentially benefiting are Brisbane, California-based VaxGen, which is working on anthrax, and San Diego-based Hollis Eden, which has developed a drug for use after a nuclear attack.

“We have to put the threat in context, and regrettably the context is serious,” said Sen. Judd Gregg, a New Hampshire Republican and chairman of the Senate Health, Education, Labor and Pension Committee and a lead sponsor of the bill.

“There is no commercial demand for this kind of commodity,” Gregg said. “We had to set up a structure where we make it viable for our private sector…to invest extraordinary amounts of money to invest in this.”