(AP) -- U.S. scientists hope to have a key ingredient for a swine flu vaccine ready in early May, but tell The Associated Press that the novel virus grows slowly in eggs - the chief way flu vaccines are made.
Even if all goes well, it still will take months before any shots are available for the necessary safety testing in volunteers.
Dr. Jesse Goodman, the Food and Drug Administration's swine flu chief, said Tuesday that scientists are working, in his words, "at 100 miles an hour" to create good raw material to deliver to vaccine manufacturers.
The researchers must engineer a strain that could trigger the immune system without causing illness. At the Centers for Disease Control and Prevention, flu vaccine chief Dr. Ruben Donis says that work is about a third completed.
©2009 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
Explore further: Scientist considered father of birth control pill dies