London ? A British company reported Wednesday it had achieved the best results ever seen on an experimental human vaccine for bird flu and said mass production might be possible by 2007.

If future tests are as promising, it would be a major step in the frustrating campaign to protect people from a possible deadly flu pandemic.

The U.S. government’s chief infectious disease scientist was very optimistic.

“The data are really very impressive,” said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases. “It changes the whole complexion of the issue that we have to face of getting enough vaccine for people who might need it in a pandemic.”

Glaxo’s results came from tests on 400 people in Belgium, most of whom developed strong immune responses from very low doses of the prototype vaccine.

Glaxo said two shots of its vaccine provoked strong responses in more than 80 percent of people tested at lower doses than other experimental bird flu vaccines are using. Some received as little as 3.8 micrograms, said Fauci, who has seen the test results on the vaccine.

“It’s pretty strong,” he said.

The Glaxo vaccine includes an immune-system booster that allows it to use less of the main active ingredient, meaning that greater quantities could be produced if the H5N1 bird virus mutates into a form that spreads easily among people and causes a global epidemic.

The vaccine uses an inactivated version of the newer strain of H5N1, which was isolated in Indonesia last year.

“It’s a good and exciting piece of science,” said Dr. David Nabarro, the United Nations’ coordinator for avian and pandemic influenza.

“But as with all new discoveries, quite a lot of work has now got to be done to establish its place in public health and pandemic preparedness.”