Bird flu virulence key concern for scientists
No one can predict when or where a bird flu virus will mutate into a human pandemic strain, but scientists are preparing so that when it does, they will be ready to pounce on it, a leading virologist said on Friday.
While surveillance centres dotted around the globe are keeping an eye on changes in the H5N1 bird flu virus, Dr Jim Robertson and scientists at the National Institute for Biological Standards and Controls (NIBSC) in England are working on vaccines in case it becomes highly infectious in humans.
"The big concern about H5 is that it is so virulent, so highly pathogenic. If that virus gets into the human population and retains that virulence you could imagine what would happen,” he told Reuters.
The NIBSC is one of a few centres in the world, which works with the World Health Organisation to provide materials to industry to make vaccines.
If a pandemic strain is identified, NIBSC researchers will be on the front line in developing tools for an effective vaccine.
So far, H5N1, which has killed more than 60 people in Asia, has not mutated to become highly infectious in humans.
But NIBSC scientists have made a vaccine using the H5N1 strain from a Vietnamese patient. They do not know it will work against a pandemic strain but are hoping it will provide some protection until a vaccine against the pandemic strain can be produced, which could take up to six months.
U.S. scientists have also produced an H5N1 vaccine, and early trials have shown it produces an immune response in healthy people.
“If necessary, even before a pandemic, we’ll start making fresh vaccine strains. We will be following it along, and hopefully be keeping up with it. If, when a pandemic strikes and it is H5, we’ll pounce on that virus immediately,” Robertson said.
TOO LITTLE OR TOO MUCH
NIBSC scientists used a technique called reverse genetics to disarm the virus and speed up the vaccine process.
The H5N1 vaccine has been supplied to vaccine manufacturers worldwide who are in various stages of producing it and running clinical trials, he said.
“Because humans have never seen H5 before, the result is we are going to need a much bigger dose of vaccine than you give annually with current human strains.”
Early research suggests it could take six times the normal dose of a seasonal flu shot. Two doses probably will be needed - one to prime the immune system and a second to raise antibody levels.
“What we need now are clinical trials. If we put in too little ... we are going to be underprotected. If we put in too much we are wasting the vaccine, which is going to be a rare commodity if a pandemic comes along,” Robertson explained.
Scientists also do not know if an underlying immunity is being developed in people in southeast Asia who are exposed to the virus but do not get ill or develop symptoms.
“There is a huge question mark. If there is, if people had a tiny bit of immunity, the vaccine would boost it,” Robertson said.
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