June 12, 2008 / 8:26 AM / 10 years ago

New-style bird flu vaccine shows promise

WASHINGTON, June 11 (Reuters) - A new-style bird flu vaccine made using monkey cells instead of chicken eggs appears to be safe and effective, corporate researchers reported on Wednesday.

The vaccine against H5N1 avian influenza, made by Baxter International (BAX.N), is the first bird flu vaccine to be made using cells in a lab dish instead of chicken eggs. This is important because the right type of chicken eggs are difficult to obtain — and because H5N1 kills chickens rapidly.

The trial of more than 250 people was a phase I/II safety trial, but the report, published in the New England Journal of Medicine, showed the vaccine produced a strong immune response in people who received two doses.

Adding an immune system booster called an adjuvant did not make the vaccine work any better, Dr. Hartmut Ehrlich, vice president of global research and development for Baxter’s BioScience business and colleagues, found. This was puzzling as adjuvants have helped other bird flu vaccines,

The H5N1 avian flu virus has become firmly entrenched among birds in much of Asia and parts of Europe, Africa and the Middle East. It rarely infects people but it has killed 241 people in 15 countries, according to the World Health Organization.

Experts fear the constantly mutating virus could change into a form easily transmitted from person to person, perhaps sweeping the world and killing millions.

At least 16 companies are working on vaccines against H5N1. No one knows if they will work against whatever strain might eventually cause a pandemic, but makers agree it is better to be prepared.

One serious hold up had been the use of fertilized chicken eggs, which are used to produce all influenza vaccines.

"Embryonated eggs are available only seasonally, which creates a time constraint in the manufacturing of yearly vaccine and certainly could influence preparedness for a pandemic," Dr. Peter Wright of Vanderbilt University Medical Center wrote in a commentary.

Cell-based vaccines would require less advance planning and could be made year-round, he said.

Baxter also has a seasonal flu vaccine made in cells instead of eggs.

"Cell culture technology could represent the future of influenza vaccine production," virologist Dr. John Oxford of The Queen Mary School of Medicine in London said in a statement.

The vaccine, called Celvapan, is made in Bohumil in the Czech Republic.

Because it is not possible to test whether the vaccine actually prevents infection, the researchers measured antibodies in their volunteers in Austria and Singapore. They said it induced an immune response similar to the body’s defense against a natural virus infection. (Reporting by Maggie Fox, editing by Alan Elsner)

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