Flu Vaccine's Egg-Free Future : The Two-Way As millions of people search in vain for swine-flu vaccine, some have no doubt asked themselves : is there a better way to make flu vaccine than relying on growing the virus in chicken eggs?
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Flu Vaccine's Egg-Free Future

Chinese factory workers check eggs in which flu virus will be grown to make the swine-flu vaccine at the Sinovac Biotech Ltd. plant in Beijing, China, Sept. 15 2009. Imaginechina via AP Images hide caption

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Imaginechina via AP Images

Chinese factory workers check eggs in which flu virus will be grown to make the swine-flu vaccine at the Sinovac Biotech Ltd. plant in Beijing, China, Sept. 15 2009.

Imaginechina via AP Images

As millions of people search in vain for swine-flu vaccine, some have no doubt asked themselves : is there a better way to make flu vaccine than relying on growing the virus in chicken eggs?

After all, one of the reasons there's not enough vaccine at present is that it's taken longer than to grow the virus in eggs than the manufacturers and health officials had expected.

NPR's Robert Siegel, a host of All Things Considered, interviewed Robert Belshe, director of the Center for Vaccine Development at St. Louis University School of Medicine to learn about the future of vaccine production.

The old-fashioned method of making flu vaccine, which has been used for at least 50 years, is the method largely used around the world, requires millions of fertilized eggs into which the virus is injected, then grown.

In 1957, Eli Lilly and Co. workers in Greenfield, Indiana used the same method as that would be used more than 50 years later to make flu vaccine. AP Photo hide caption

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AP Photo

In 1957, Eli Lilly and Co. workers in Greenfield, Indiana used the same method as that would be used more than 50 years later to make flu vaccine.

AP Photo

ROBERT: Part of the process when the country orders up a bunch of vaccine is you've got to get those roosters and hens to work.

BELSHE: That's right. These are not the ordinary eggs you buy in the grocery store which are generally not fertilized. But it requires a fertilized hen's egg.

So you've got to have a rooster and a hen get together, do their thing, then the eggs have to be laid. And then they have to be incubated until 10 days old for the idea culture medium.

It takes one egg to make an injectable dose of flu vaccine but the same egg can produce hundreds of doses of the inhalable form of the vaccine.

Not only is the the egg method time-consuming but it is subject to the vagaries of agriculture. Also, if a pandemic flu of the avian variety arrives on the scene, the chickens who lay all those eggs could be susceptible, further slowing production.

So vaccine manufacturers are working on new methods, which Robert asked about.

For instance, one method would grow the virus used to make the vaccine in tissue culture, like dog kidney cells, Belshe said.

On hearing this, Robert asked the question that was probably on a lot of dog lovers' minds.

ROBERT: Would large numbers of dogs be sacrificed to make a batch of flu vaccine?

BELSHE: No, you don't have to sacrifice the dog in order to make a tissue culture. This tissue culture has been in existence for many, many years and the cells can be grown essentially forever in the laboratory. So no animals need to be sacrificed.

Belshe also mentioned the use of recombinant DNA technology as another approach to speeding up the vaccine manufacturing process. Scientists are also working on using insect cells, specifically from caterpillars, in which to grow the vaccine Belshe said.

In terms of the time to produce the material that's purified into vaccines, with eggs it takes two months and that's if all goes well.

The other methods by contrast can take a few days to achieve the same results, Belshe said.

By the way, it shouldn't have been a surprise that there'd be a shortage of swine-flu vaccine this fall. Last spring, some experts were warning that due to the chicken and egg intensive methods currently used to produce the vaccine in bulk, there could very well be shortages.

Meanwhile, there are some useful material on the web to help those wanting to learn more about new flu vaccine production methods under development.

Novartis, the pharmaceutical company, has this promotional but informative fact sheet on its efforts.

Another article that provides useful background was written by two executives of British biopharmaceutical firms.

Meanwhile, an article on the University of Rochester Medical Center site gives a better understanding of the use of caterpillar cells to make vaccine.