Chinese scientists announced on Wednesday that two newly developed vaccines are capable of stopping the spread of the deadly H5N1 strain of the bird flu virus. Experiments show that the vaccines are 100 percent effective.
Chen Hualan, director of the China National Bird Flu Reference Laboratory, based in Harbin, capital of Heilongjiang Province, said the two new vaccines developed by her lab had proved to be a success, having passed a state-level appraisal, and obtained a permit granted by the Chinese Ministry of Agriculture (MOA) to put the vaccines on the market.
"Experiments show that the efficiency rate of the newly developed vaccines in preventing infection by the H5N1 virus is 100 percent," said Chen.
In the meantime, China has developed three new technologies, including the indirect immune fluorescence diagnose and virus antigen capture technology as well as the RT-PCR method that work together to confirm a bird flu epidemic in less than 10 hours. Previously, it took some 72 hours to do this.
More of the two new vaccines have been sent to Gangcha County in northwest China's Qinghai Province in a bid to prevent the deadly avian disease from spreading. Carcasses of migratory birds, confirmed by Chen's lab to have been infected by the deadly H5N1 virus, were found here on May 4.
The Chinese Ministry of Agriculture also made an announcement about the incident last Saturday. It is the first reported bird flu case on the Chinese mainland since last year when China successfully wiped out the primarily avian-borne epidemic disease.
Sources said some of the dead migratory birds discovered in Gangcha County had migrated from Southeast Asia. Migration is blamed for exacerbating the spread of the virus.
There is a high risk of cross-infection from infected migratory birds to waterfowl to domestic fowl and even to humans.
However, there have been no previous reports of vaccines being tested on waterfowl before China began its research. The latest experimental results show that the newly developed vaccines of Chen's lab are equally effective in waterfowl, including ducks and geese, which when inoculated with the vaccines did not develop bird flu symptoms.
"With the vaccines, one activated and the other inactivated, the channel for the spread of bird flu virus can be cut off," said Chen.
Compared with conventional vaccines, the virus-inactivated vaccine provides stronger protection against infection in waterfowl such as ducks and geese upon inoculation, while the effects of inoculation in chickens last an additional four months. The virus-activated vaccine can provide protection within nine months after inoculation.
"The meat of fowl inoculated with the vaccines have been shown not to be affected," said Chen.
An estimate made in February 2004 by UN Food and Agricultural Organization (FAO) said about 100 million domestic fowl died either because they were infected with the H5N1 virus or were culled. Direct economic losses were placed at US$500 million.
At least 52 people in Vietnam, Thailand and Cambodia who were infected with the virus died as a result.
The World Health Organization (WHO) has warned that over one million more people could die if the H5N1 virus were to spread from human to human. Human deaths caused by the common flu each year are between 250,000 and 500,000, but scientists believe mortality rates in the event of a bird flu epidemic in humans could be much higher.
According to Chen, some chicken farms in Vietnam have been conducting safety and effectiveness experiments with the new vaccines.
Agricultural officials in Vietnam said they would inoculate all their domestic fowl with the new bird flu vaccines once the experiments prove positive.
"We will spare no effort in offering support to other countries if necessary," Chen promised.
(Xinhua News Agency May 26, 2005)
