Can We Fend Off Bird Flu?

A study being published in Thursdays New England Journal of Medicine provides disappointing news on the avian flu front. The good news is that the study of 451 healthy adults shows that a vaccine manufactured by Sanofi Aventis using current standard techniques is safe. The bad news is that the inoculation will most likely be effective in humans only at the highest doses. Furthermore, the results show that the vaccine — as it is currently constituted — would take two and perhaps three injections to achieve good protection. That is a problem, since the U.S.s already modest stockpile of material to make an avian flu vaccine wont stretch very far. In order to make the vaccine practical for a wider population, the scientific community, business and government must work together to figure out how to make the vaccine more effective at lower doses.

"We had hoped the result would be better than this," says Dr. John Treanor of the University of Rochester in New York. But Treanor, who led the study, says he was neither surprised nor discouraged by the result. A previous test of a more experimental avian flu vaccine reached a similar conclusion last year.

Specifically, the NEJM study showed that it takes 90 micrograms of active ingredient in each of at least two doses of vaccine to get the best result. By contrast, the current seasonal flu vaccine contains 45 micrograms of active ingredient — from three different strains of flu virus — and you need only one shot to achieve good protection against all three strains of the flu virus. "Having a vaccine that would require 90 micrograms times two in and of itself would not and cannot be the answer to where we want to be," Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said in a press teleconference. "Its a step to where we want to be, but it is a small step."

Then there is the matter of having the right strains of virus in the vaccine should a human pandemic ever occur. The virus used to make the Sanofi Aventis vaccine came from a Vietnamese patient who was infected with H5N1 in 2004. The viruses from that sample are part of a group that scientists call clade 1. But the viruses that have recently spread so rapidly among birds from Asia to Europe and Africa are part of a new group called clade 2. Preliminary evidence suggests that theres not a lot of cross-reactivity between the two clades. That means that a person who has become immune — through sickness or inoculation — to an H5N1 virus from clade 1 would still be vulnerable to a clade 2 viral infection.

At least, however, researchers have established a baseline of what is currently possible and what still needs to be done to create an avian flu vaccine for people. Already there are other studies under way to see if the dosage can be reduced by adding so-called adjuvants — like aluminum hydroxide or another compound called MS59 — to boost the vaccines effectiveness. Aluminum hydroxide has been used as an adjuvant previously in the U.S., whereas another compound called MS59 has been used in Europe.