Experts said the successful development of a vaccine virus for the H7N9 bird flu virus means China can use it to produce its own H7N9 vaccine.

"This means we don't have to depend on foreign vaccine viruses for producing H7N9 vaccine," said Li Lanjuan, director of the State Key Laboratory for Diagnosis and Treatment of Infectious Diseases. "Before this, China had not developed a flu vaccine virus, and needed vaccine viruses from abroad to produce vaccines for all kinds of flu, including H1N1 flu.

"It's much slower if we take them from abroad to make vaccines," said Li, a leading researcher from the Chinese Academy of Engineering,