HONG KONG: Scientists at the University of Hong Kong now prepare to move to the next phase of testing of the vaccine that could protect the world against a deadly bird flu pandemic.

The research team headed by microbiologist Leo Poon, buoyed by the knowledge that their vaccine is effective, inexpensive and capable of rapid mass production, soon will begin laboratory tests on monkeys.

The announcement late last month that scientists from the University of Hong Kong and a team of American scientists had developed a vaccine capable of protecting humans from the deadly H5N1 avian flu virus brought immense relief around the world.

H5N1 has proven lethal to more than half the human victims who came into contact with infected birds. The greater fear however was that the virus, according to the nature of all influenza viruses, could mutate, so as to become transmissible from human to human, thus unleashing a global scourge that could kill millions.

Doctor Poon from the University of Hong Kong says one of the principal virtues of the new vaccine is that it derives from smallpox vaccine which already has been proven safe for humans.

The vaccine also offers several other advantages for addressing the H5N1 threat and staving off a pandemic should the virus mutate.

Existing bird flu vaccines are expensive, toxic and dependent on a supply of eggs, while their effectiveness in treating humans is unproven, Dr Poon said. The new vaccine promises effective protection for humans, he added.

"A single dose will provide rapid protective immune responses," he claimed.

Mass production of the new vaccine could be achieved using cell-cultures instead of having to rely on an available supply of eggs, Dr Poon said.

The vaccine could also be manufactured with existing vaccine production facilities to help reduce the costs, he added.

In laboratory tests, the new vaccine provided complete protection to mice injected with the H5N1 virus.

The incorporation of a kind of human gene in the tests also improved antibody and cellular immune responses of mice against H5N1.

"The new vaccine can offer a solution in case of an outbreak of a bird flu pandemic," he said.

He said a few H5N1 bird flu vaccines have been licensed in Hong Kong but they are not yet on the market.

He said it falls to pharmaceutical companies to determine the per dosage cost of the new vaccine, but he stressed it would be less expensive than current options.

The next target of the research group is to test the safety and protection of the new vaccine on monkeys. The testing will be carried out over the next two to three years.

The teams will also extend their research, endeavouring to identify a "universal influenza vaccine" that provides protection against a range of subtypes of the bird flu virus.

According to the World Health Organization, the H5N1 bird flu virus has infected over four hundred people around the world. More than half who have contracted the virus died.

There have been no known cases of human to human infection from the H5N1 virus.

The three-year study that led to the vaccine was carried out in collaboration with scientists at the National Institute of Health, USA. Results of the study were published in the March 2009 issue of The Journal of Immunology.

(HK Edition 03/10/2009 page1)