HANOI (Reuters) - Vietnam has started clinical trials fordeveloping a human vaccine for the H5N1 virus, researchers saidon Thursday in the Southeast Asian country that has recorded 52deaths from bird flu.

Eleven volunteers, all researchers, received their seconddosage of the trial vaccine on Thursday inside spotlessly-cleanmedical rooms of a company run by the National Institute ofHygiene and Epidemiology in Hanoi.

Dr Nguyen Tuyet Nga, the epidemiologist and virologistheading the clinical trial, said researchers were using thehighly-pathogenic strain of H5N1 taken from humans in 2004 inVietnam and known as VN1194.

The strain is being studied worldwide by scientists intheir quest for a vaccine for the bird flu virus that haskilled 238 people globally out of 376 confirmed cases since2003, according to the World Health Organization.

"I think this is complicated but very important work and wehave some support from outside experts," Nga said. "We willtest it for cross-protection in a later clinical trial but notnow."

She said the U.S. Centers for Disease Control and the WorldHealth Organization (WHO), a United Nations agency, had helpedwith project development, but there was no foreignpharmaceutical partner.

The dosages for the clinical trial range from 3.75micrograms to 45 micrograms per dose and two doses 28 daysapart, Nga said. She said there were no boosters planned forthe trial.

"We´ll see how long protection lasts," Nga said afterreceiving a dosage and administering it to other volunteerswearing white or green medical coats and blue surgical caps atthe company known as Vabiotech.

"It feels and looks like any other vaccine," said Hoang AnhDuc, 25, one of the volunteer researchers.

Last month, a military official said the Vietnam Ministryof Health had approved another trial to start later in April atthe Military Medical Academy in Ha Tay province near Hanoi.

Researchers at Vabiotech, or Company for Vaccine andBiological Production No.1, said on Thursday that up to 30military personnel were expected to volunteer for that trialonce it was approved by the Ministry of Defense.

WHO in Vietnam said it was not directly involved in theCommunist-run country´s development of a human vaccine for theH5N1 virus, but was satisfied that health authorities hadrigorous guidelines for quality control.

GlaxoSmithKline said last month that a vaccine it designedto protect people against H5N1 may be effective in warding offa few different sub-types of the virus.

A vaccine designed using a current H5N1 strain might notoffer protection against other strains and might even beuseless in any eventual pandemic because viruses mutate all thetime.

Still, experts say the process of making vaccines will laydown the necessary infrastructure so that the time used to makean eventual pandemic vaccine -- anywhere between 4 to 6 monthsafter a pandemic begins -- can be shortened.

(Additional reporting by Nguyen Nhat Lam; Editing by JohnChalmers)