French Bird Flu Vaccine No Panacea
Immune Boost Lowers Vaccine Dose, but Much More Work Ahead
WebMD News Archive
The Good/Bad News continued...
At the highest dose tested, the plain-vanilla version of the vaccine
elicited levels of anti-bird-flu antibodies expected to be effective in 52% of
volunteers. When given with alum, the high-dose vaccine was 67% effective.
Unexpectedly -- and disappointingly -- the alum adjuvant did not boost
immune responses to lower doses of the vaccine. That may be because alum is
simply not a very good adjuvant, suggests immunologist David Topham, PhD, of
the University of Rochester, N.Y.
"Anything approved for human use is judged on side effects and
reactions," Topham tells WebMD. "If it is benign in not causing a lot
of negative reactions, it gets approved. Alum is good in that regard. But as an
adjuvant, it is not very good at all. It is arguable whether it is better than
not using an adjuvant at all, judging from this data. And it didn't work at all
at the lower doses."
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.