WASHINGTON -- The nation apparently has more smallpox vaccine than previously thought: New research shows 15 million doses in a government stockpile can be stretched to make up to 10 times more inoculations -- and the government may buy millions more doses discovered in a drug company's freezers.

Both discoveries are important because while the nation has ordered 200 million new doses to be made by a British company, they won't arrive until at least year's end -- and then must pass testing to ensure they're effective.

Having more vaccine on hand would buy more time to ensure the new production is done properly.

More immediately, Thursday's studies backing plans to stretch today's vaccine proves the government's stockpiling is on track, Health and Human Services Secretary Tommy Thompson said.

"We hope our smallpox vaccine stockpile will serve as a deterrent to those who may consider using smallpox as a weapon," he said. "We will have the necessary medicine to save and protect every American should there be an outbreak."

The nation quit routine smallpox vaccination in 1972, and the disease was declared eradicated worldwide in 1980.

But the U.S. and Russian governments hold stocks of the deadly virus, and bioterrorism experts worry that samples could fall into terrorists' hands and be used as a weapon, although Thompson said Thursday the risk is low.

If an attack occurred, doctors would quickly vaccinate people in the vicinity, because inoculations up to four days after exposure still offer protection.