An Australian company said on Monday it was confident the vaccine it was testing in humans could protect against a pandemic form of the H5N1 bird flu virus unless it undergoes major genetic changes.
CSL Ltd, the world’s largest maker of blood plasma products, has begun human vaccine trials using different dosages and hopes to know results by next February.
If the trial is successful, the company says it can produce a vaccine against a pandemic form within three months if H5N1 mutates into a form able to be transmitted human-to-human, and in six months if a totally new strain emerges.
The virus has already killed more than 60 people in Asia and spread to Europe. Scientists say it is only a matter of time before it mutates into a form than can cause a pandemic that could kill millions of people.
“The mutation that would make it spread from human to human, which is what we’re worried about, is probably not enough to render the vaccine ineffective,” said CSL research and development spokeswoman Rachel David.
Other experts, however, have said that the H5N1 strain of bird flu could move too quickly for drugs and vaccines if it begins to easily infect humans.
The H5N1 strain, like all viruses, mutates continually but the changes are usually very small. A pandemic form of the virus can occur through steady mutation or through a process called genetic reassortment.
This occurs when two different strains, for example a human flu virus and a bird flu virus, infect the same cell and swap pieces of genetic material.
David said a vaccine could still be ready within six months if dosage formulations it was using in its vaccine trial were shown to be inadequate or if a completely new strain of the virus emerged somewhere in the world.
“That second scenario is much less likely. The most likely scenario that would blow out the time would be if the dose that we need was higher than expected,” she said.
Otherwise, if the trial proves the vaccine is effective and the dosages are correct, then it could be produced in large quantities within three months.
She said CSL was working on trials using two injections of 7.5 micrograms of viral antigen and two 15-microgram injections while also using adjuvants, or substances which help enhance the body’s immune response to antigens.
Vaccine trials elsewhere, such as in the United States, have not used adjuvants and therefore required much higher levels of antigens which were consequently harder to produce, CSL said.
“We made assumptions about what these doses will be, knowing there is a relationship between the dose’s active ingredient in the vaccine and how quickly you can produce it for a large number of people,” David said.
The Australian government gave CSL A$5 million ($3.8 million) in July to fast-track development of a vaccine.
“Our research goal is actually to vaccinate the entire population,” David said. Australia has 20 million people.
“We could make a vaccine tomorrow that would guarantee immunity in a small number of people but for us that’s useless.
“For us the goal is to vaccinate a large amount of people very, very quickly,” she said.
CSL’s chief scientific officer Andrew Cuthbertson said an alternative to their current approach was to use a weaker vaccine to minimize the severity of the illness but not completely prevent it.
He told The Sydney Morning Herald on Monday that approach might save lives but added it was up to policy makers to decide on what was an acceptable level of protection.