Enthusiasm over the news that U.S. researchers had proven a vaccine is effective against the H5N1 avian flu strain was tempered yesterday with word that it took massive doses -- roughly 12 times the normal amount -- to produce a protective response in humans.
With global vaccine production capacity already falling far short of what would be needed in a flu pandemic, experts suggested it is critical to increase research into ways to produce the same response with smaller doses of antigen, the substance in a vaccine that activates the immune system.
"I think these results suggest the world is even less prepared than more prepared," said Michael Osterholm, director of the University of Minnesota's Center for Infectious Disease Research and Policy.
"And unfortunately many policy-makers might take this announcement as being 'We've hit the gold mine' -- when in fact I would suggest we are having a hard time even finding water."
In light of the U.S. findings, federal health officials said studies into a yet-to-be-made Canadian H5N1 vaccine will be focused on the role antigen-sparing techniques could play in pandemic vaccine production.
It's hoped those studies will begin late next summer.
"It's something that we are definitely considering in the design, because of what we know, that it could take lots of doses," said Theresa Tam, associate director of respiratory diseases at the Public Health Agency of Canada.
"It's of great interest to us to look at these types of antigen-sparing strategies, whether it be adjuvants or whole viruses."
Adjuvants are chemicals that, when mixed with vaccine, kick the body's immune response up several notches, allowing a smaller dose of vaccine to produce a bigger effect.
Vaccines made of whole viruses, rather than viral particles, are known to provoke greater immune responses as well but are also known to produce more side-effects on administration.
February's federal budget set aside $34-million for production of trial batches of an H5N1 vaccine. But Canada's flu vaccine manufacturer, ID Biomedical, has still not been given the go-ahead to do the work.
"We're close to entering into a contract. Hopefully, it will be done shortly," Health Minister Ujjal Dosanjh said yesterday.
The company has said it would take 12 months from contract signing to vaccine delivery, because it must build and license a special high-biosecurity facility within its existing vaccine plant.
Public Health Minister Carolyn Bennett said yesterday that the apparent success in developing an avian-flu vaccine will not in itself eliminate the risks of a global influenza pandemic.
In a telephone interview from Hong Kong, where she is attending a meeting about pandemics and public-health issues, she noted that mutations of influenza viruses occur rapidly and that the next threat may in fact come from a different strain.
With a report from Jeff Sallot in Ottawa and AP
