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Bypassing Eggs, Flu Vaccine Grown in Insect Cells Shows Promise

The vaccine against influenza is typically grown in chicken eggs. But an experimental vaccine made in insect cells appears to be as safe and effective as conventional vaccines.

In research led by John Treanor of the University of Rochester Medical Center in New York, an insect virus known as baculovirus was used to grow key components of the flu virus in cells originally derived from caterpillars. Treanor says it's safer than the current approach, which uses live flu virus. "Working with the live pandemic virus to make vaccines carries with it some risk that you won't contain it well," he says, explaining the risk can be lessened somewhat by manipulating the viruses so they're not so pathogenic. "But the nice thing about the baculovirus approach is that there's no influenza involved at all, it's just the gene for the important vaccine antigen."

It also does not require eggs, which could be in short supply as the world faces the threat of pandemic bird flu.

Treanor says another advantage of using insect cells is speed; the new method is quicker. "You might get to the point where you had the vaccine in vials ready to administer to people a few weeks earlier using this approach, rather than the traditional approach," he says, adding "that's useful because there's a very limited window of opportunity to get people vaccinated every year, and even saving just a few weeks could have an impact of vaccination programs."

The vaccine was tested on a small group of healthy volunteers, ages 18 to 49. The researcher says, "If you compare the number of people who got flu in the placebo group, people who had not been vaccinated, with the number of people who got the flu in the vaccine group, the vaccine reduces the rate of flu by 85%." That compares favorably to what you might see with the regular flu shot.

Treanor says the next step is to repeat the study with a larger group of subjects. Results of the initial study appear in the current issue of the Journal of the American Medical Association.