HONG KONG (Reuters).- An experimental bird flu vaccine that uses DNA from various strains of the H5N1 virus appears to trigger a strong immune response in mice after it is injected straight into the muscles, a study has shown.

In the journal Cell Research, scientists in Taiwan and the United States said the vaccine protected mice fully against H5N1 strains from Vietnam, Turkey and China's eastern Anhui province.

"We injected it into mice and after more than a week, the mice were immunized and we challenged the mice with live virus strains from Vietnam, Indonesia, Turkey and Anhui," Chi-Huey Wong from The Genomics Research Center in Taiwan's Academia Sinica told Reuters by telephone.

"The mice were fully protected from the strains from Vietnam, Turkey and Anhui, while 80 percent (of mice) were protected from the Indonesian strain, but that's still very high."

Another group of mice which were not immunized all died within days of being infected with lethal doses of the virus.

Vaccines using DNA are a departure from the traditional way vaccines are made -- painstakingly grown in chicken eggs, which could well be in very short supply in the case of a pandemic.

The H5N1 avian influenza virus currently mostly affects birds and is endemic in flocks in many parts of Asia. It has also swept through flocks in Africa and occasionally in Europe.