This Monday, the Chinese vaccine maker Sinovac Biotech Ltd. announced that its H5N1 flu vaccine induced immune responses in a midstage study.

The study was conducted on 402 volunteers who were vaccinated with two doses each of 5, 10 or 15 micrograms. It was a phase II clinical trial that proved to be successful. The company intended to obtain in this trial safety and prompting immune responses. The results showed that responses for the 10 and 15 micrograms doses reached European regulatory evaluation standards for seasonal flu vaccines. The first clinical trial had also positive results.

There were no serious adverse reactions among the 402 volunteers aged between 18 and 60.

Last week, another company that works to develop effective vaccines against bird flu, Novavax Inc., Rockville, M.D. based, announced that its early phase trial of an experimental H5N1 flu vaccine proved successful, inducing promising immune responses in patients. Novavax shares fell 3 cents to $3.51, but Sinovac shares rose 14 percents to $4.62.

The H5N1 strain had been found in 2003 when infecting Asian poultry stocks. Since then, about 209 people have died worldwide from this virus, linked to infected birds. Since then, scientists and companies have worked to develop a vaccine that would prove effective in case of pandemic bird flu.