French Bird Flu Vaccine No Panacea
Immune Boost Lowers Vaccine Dose, but Much More Work Ahead
Dose-Sparing Technology -- or Different Technology?
Fortunately, Topham says, better adjuvants are being tested by his
colleague, John Treanor, MD, who leads clinical trials of some experimental
flu vaccines in the U.S. Saville says Sanofi Pasteur is also
exploring the use of better adjuvants.
Of course, better adjuvants mean stronger immune responses -- and probably
more side effects.
"There are a lot of adjuvants out there, but whether they can get FDA
approval is not clear," Topham says. "If there were a pandemic, we
might tolerate some side effects we would otherwise not accept."
Adjuvants are only one way that bird flu vaccines might be improved. In an
editorial accompanying the French report, CDC researcher Suryaprakash Sambhara,
PhD, and Mayo Clinic researcher Gregory A. Poland, MD, note a few alternatives
are now on the drawing board.
Vaccine proteins might be incorporated into immune-stimulating complexes
(ISCOMs) or into fat bubbles (liposomes) that stimulate strong immune
responses. Or a live-virus vaccine -- such as the currently approved FluMist --
might be adapted for bird flu use.
These strategies may be important, as bird flu has now divided into two
separate lineages or clades. Emerging evidence suggests that vaccines against
one clade may not work against the other.
But what might be considered "effective" is also open to debate.
Saville and colleagues note that seasonal flu vaccines have to prevent
infection or disease in order to be effective. A bird flu vaccine, however,
might be considered effective if it only prevented severe disease and death
during a pandemic.
Even so, the new report shows that bird flu vaccines still have a long way
to go before they offer more than a passing chance of protection for a
relatively small number of people.