Cold, Flu, & Cough Health Center

French Bird Flu Vaccine No Panacea

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.

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.