French Bird Flu Vaccine No Panacea
Immune Boost Lowers Vaccine Dose, but Much More Work Ahead
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 bird 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.