Dr. Marie-Paule Kieny, director of the WHO initiative for vaccine research said yields of antigen -- the crucial component in vaccine production -- are larger than companies had expected, the Los Angeles Times reported.
"I don't want to say too early that the question has been resolved, but it really seems like we have found a way to go around this problem," Kieny said at a news conference in Geneva.
However, preliminary studies suggest the antigen used in the vaccine for swine flu does not provoke as strong a response as the seasonal flu vaccine and it may be necessary to use two doses -- halving the number vaccines.
European manufacturers are attempting to be able to use one vaccine by using adjuvants -- chemicals that stimulate the body's immune system to react more strongly to the vaccine -- but no flu vaccines containing an adjuvant have ever been approved in U.S. Food and Drug Administration.
