TRENTON, N.J. - A small study conducted by federal scientists shows Novavax Inc.'s experimental vaccine against swine flu, produced in just weeks versus several months for standard methods, is effective in animals, the company said Tuesday.

But it won't be approved and ready for commercial use in the U.S. for at least a couple years, meaning the vaccine won't be available to help here in the current epidemic of novel H1N1 influenza, company officials said.

Novavax, based in Rockville, Md., makes vaccine using what's called virus-like particle technology to build a structure like a virus, but without the genetic material inside that a virus needs to reproduce. The particles -- sets of proteins assembled through genetic engineering -- are injected and attach to immune cells, which recognize the particles like they would a virus.

That stimulates a strong immune response, the company said.

Traditional influenza vaccines, which have their key ingredient incubated in chicken eggs, take several months to produce.

Chief Medical Officer Dr. Penny Heaton told The Associated Press that Novavax was able to produce its vaccine in less than four weeks.

"It demonstrates what might be possible in the next pandemic" -- or in this one if the virus became much more lethal and the government deemed it an emergency, she said.

Three of the five companies that supply seasonal flu vaccine to the U.S. market have begun testing swine flu vaccine on people in recent weeks. All those makers have been taking orders from governments in wealthy countries, and the companies have promised the World Health Organization that some of their vaccines will be reserved for poor nations.

Heaton said there still will be need for swine flu vaccine in poor countries, and her company is in talks with some about possible sales sometime in the future.

Because Novavax does not yet have any vaccines licensed in the U.S., the company would have to go through a lengthy process to get both its products and manufacturing facilities approved before it could sell its first product here.

That would take at least two to three years, Heaton said.

Novavax plans to begin testing its vaccine in people later this year, said Tom Johnston, vice president of strategy.

According to the company, scientists at the Centers for Disease Control and Prevention tested its vaccine at different doses in ferrets, which react to influenza much like people do.

Ferrets injected with a high vaccine dose that then had H1N1 virus inserted in their nose did not develop flu symptoms and had no detectable virus in respiratory secretions three days after being exposed to the virus. Ferrets that got a low dose had no detectable virus after five days, but those that got no vaccine developed fever, became lethargic and had flu virus in their secretions for up to six days.