Animal tests show Novavax flu vaccine works: company

WASHINGTON (Reuters) - A new kind of influenza vaccine works against the new swine flu virus in animals, Novavax Inc reported on Tuesday.

The company said it made the vaccine, which uses so-called virus-like particles, in fewer than four weeks after getting the genetic sequence of the H1N1 swine flu virus, which is now causing a pandemic. Most flu vaccines take five to six months to make.

Shares of Novavax shot up on the news, and were up 7.5 percent during mid-morning trading on Nasdaq at $4.86.

Novavax would have to get U.S. Food and Drug Administration approval before it could test its new vaccine in people. Years of testing are likely to be required before such a new formulation of a vaccine could be widely used in people.

The virus-like particles are a mock version of the virus, made using the genetic sequence released by the U.S. Centers for Disease Control and Prevention.

Novavax said the vaccine protected ferrets against the new pandemic strain. Ferrets are the closest animal to humans when it comes to being infected with influenza.

"The ferrets received a 3.75, 7.5, or 15 microgram dose of the 2009 H1N1 virus-like particle vaccine or a placebo and were boosted with a second dose after three weeks," the company said in a statement.

Researchers at the CDC infected the animals with H1N1 taken from a California patient. "By day five after challenge, immunized ferrets at all vaccine dose levels had cleared the H1N1 virus and showed no sign of disease," the company said.

Unimmunized ferrets became ill.

OLD-FASHIONED TECHNOLOGY

Clinical trials of H1N1 vaccine made the old-fashioned way, with chicken eggs, are under way, and five companies are making it for the U.S. market -- AstraZeneca's MedImmune unit, CSL, GlaxoSmithKline Plc, Novartis AG and Sanofi-Aventis SA.

Also on Tuesday, China's Sinovac Biotech Ltd reported China's Center for Disease Control had completed a clinical trial of its H1N1 vaccine in 1,614 people and showed it provided an immune response without adverse side-effects.

Novavax, based in Rockville, Maryland, has been using its new technology to develop a vaccine against H5N1 avian influenza.

Most influenza vaccines use either a weakened but live flu virus or a killed virus to stimulate the immune system. They must be reformulated every year to match the constantly mutating flu strains and are made using specially grown live chicken eggs.

Novavax grows the vaccine in lab dishes of caterpillar cells in a process the company says is quicker. It uses a decoy of the virus called a virus-like particle. The body recognizes the particle as a virus but it cannot infect cells and replicate.

The World Health Organization declared H1N1 a pandemic in June, and the virus has spread to about 180 countries. World health officials have said people should receive the two-dose swine flu vaccination as well as the single-dose seasonal flu vaccination this year.

In July, U.S. advisers said about half the U.S. population, or 160 million people, should get vaccinated against the new pandemic influenza strain, with pregnant women and healthcare workers at the front of the line.

But the U.S. Health and Human Services Department has said it can only get about 45 million doses of flu vaccine by mid-October, and about 20 million doses a week after that.

(Editing by Eric Beech)