Researchers have announced in this week's New England Journal of Medicine the development of a new bird flu vaccine which can be multiplied easier and faster. The traditional way of making vaccines is by using the embryos of hens' eggs, a method which has an inherent disadvantage: chickens lay most of the eggs in the spring. Thus, production in other times of the year is extremely difficult.

With the classical vaccine production method, using the embryos of hens' eggs, it takes around 22 weeks for the vaccine to be made. This can be too long should a pandemic break out. The researchers developed a method which involves green monkey cell lines, yielding the vaccine in just 12 weeks.

The new H5N1 vaccine was tested by Baxter Bioscience researcher Hartmut J. Ehrlich, MD, and colleagues on 275 people. They noticed the two-shot series provided 76 percent immunity to the bird flu virus, much better than other vaccines. The explanation lies in the fact that Ehrlich's team used whole virus that has been killed by chemicals and ultraviolet light, rather than virus fragments as is the case with competing vaccines.

Baxter is one of many companies rushing to develop an effective and easy to produce bird flu vaccine, which might be a gold mine should a pandemic occur. Baxter's vaccine, called Celvapan, is made in Bohumil in the Czech Republic under strict safety conditions, in biosafety level 3 laboratories.