Scientists are reporting in this week's New England Journal of Medicine that they have made an experimental vaccine against pandemic avian flu that is not only potent, but one that can be stockpiled quickly.  The drug is created using the cells of monkeys instead of chicken eggs.  VOA's Jessica Berman explains.

Millions of doses of stockpiled vaccine to protect people around the globe against a highly virulent H5N1 bird flu pandemic, if and when one should occur, are made using the embryos of hens' eggs. 

"Although it is the best we have, it's probably not in my opinion - and this is very much a perspective that reflects my opinion - is not yet where we want to be in terms of having a vaccine that we want to roll out in the next several months to a year if we had to," explained Peter Wright, a professor of pediatrics at Dartmouth College in Hanover, New Hampshire.

Wright says because chickens lay most of the eggs in the spring the vaccine production method, which was developed a half century ago, limits how many doses can be produced.

The eggs are used to grow the virus to make the vaccine that prompts the immune system to target the disease.

Writing in the New England Journal of Medicine, Wright says an experimental vaccine that's produced using monkey cells begins to address some of the problems with the current stockpiles of avian flu vaccine.

Hartmut Ehrlich, who is with Baxter Bioscience in Vienna, Austria and is the study's lead author, says using primate cells to make the vaccine could significantly reduce the amount of time it takes to manufacture the vaccine. 

"That means from the time we and other manufacturers are getting the pandemic strain for producing the vaccine it will take us about 12 weeks less," he noted.  "So that translates into three months to have vaccine ready to ship out."

In a clinical study involving 275 individuals, the two-dose vaccine protected up to 76 percent of the participants after 21 days.  Ehrlich says other experimental H5N1 vaccines are not as protective.

Meanwhile, global health officials remain concerned that millions of doses of avian flu vaccine that have been stockpiled for years in anticipation of a bird flu pandemic are beginning to lose their potency. 

Officials are calling for adjuvants, or additives, to be set aside to strengthen the vaccines.