Experimental Bird Flu Vaccine Could Be Doubly Promising

Mar 06, 05:00 AM

Current Headlines: By Anita Manning

An experimental pandemic flu vaccine appears to protect against infection with bird flu at very low doses and protects against a variant strain of the virus that doesn't match the one in the vaccine, researchers reported Monday in Hong Kong.

Scientists with GlaxoSmithKline say their vaccine against H5N1, the bird flu virus many believe could cause a human flu pandemic, causes a significant immune response at a lower dose than usually required when it's mixed with an immune booster called an adjuvant. It also protects against mutated bird flu strains, tests in animals indicate.

More studies will be needed before the vaccine can be evaluated for approval by the Food and Drug Administration, company officials said. Those tests will begin this year.

In reports presented at the International Symposium on Respiratory Viral Infections, scientists said an experimental vaccine containing 3.8 micrograms along with the adjuvant was 25 times more powerful than the same dose without the adjuvant. A second study in ferrets found the vaccine not only protected against the Vietnam H5N1 flu strain in the vaccine but also against a newer version that emerged in Indonesia.

"Those are potentially major breakthroughs," says infectious-disease specialist Andrew Pavia of the University of Utah Medical Center, chairman of the Infectious Diseases Society of America's pandemic flu committee. He is not involved with GlaxoSmithKline or its research.

Flu viruses change constantly, a process scientists call "drift." A vaccine that offers "a broad response to a drifted virus after two doses is important," he says. "It means a pre-pandemic vaccine could actually be useful because it doesn't have to be a perfect match."

And being able to make it using such low doses could have a "huge public health impact" by increasing the vaccine supply, Pavia says. "It raises the possibility you could get vaccine for those beyond the developed countries."

Last week, an FDA advisory committee recommended approval of an H5N1 vaccine made by Sanofi Pasteur. That vaccine requires two 90-microgram shots given four weeks apart to prompt an immune reaction strong enough to prevent illness.

But Pavia says the new vaccine still needs to go through FDA review, and because the adjuvant that is crucial to the vaccine's strength is new, "it means there's a lot to learn about safety. The FDA has signaled they're going to look at adjuvants cautiously," he says.

GlaxoSmithKline's Bruce Ennis, vice president of research and development for vaccines, says the license application for the company's vaccine has been accepted for review by European regulators, and "we are in discussion with the FDA" about studies needed for license applications to be made in the USA. (c) Copyright 2005 USA TODAY, a division of Gannett Co. Inc.