Dr. Nguyen Tuyet Nga, head of the high tech division of the Vietnam's Vaccine and Biological Production No. 1 company gets blood sample of a volunteer at a human vaccine trial for bird flu H5N1 virus in Hanoi April 3, 2008. Vietnam has started clinical trials for developing a human vaccine for the H5N1 virus, researchers said on Thursday in the Southeast Asian country that has recorded 52 deaths from bird flu. REUTERS/Kham (VIETNAM)