The Health, Labor and Welfare Ministry has begun a full-fledged study into developing a vaccine production method using recombinant DNA technology to fight the possible mutation of the avian influenza into a new form affecting humans, ministry officials said Thursday.

With the recent resurgence of bird flu in Vietnam and Thailand, the ministry said the prospect of a new form of human flu emerging is a "realistic" and urgent issue.

Last year, the H5N1 strain of bird flu hit Asia particularly hard, killing chickens and people.