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Vaccine Shows Promise Against H5N1 Avian Influenza

Regimen using wild-type virus grown in Vero cell culture could reduce lead time for production

WEDNESDAY, June 11 (HealthDay News) -- Two doses of a whole-virus vaccine against H5N1 avian influenza produced on Vero cell cultures induced neutralizing antibodies against multiple H5N1 strains, indicating its usefulness against this virus with pandemic potential, according to research published in the June 12 issue of the New England Journal of Medicine.

Hartmut J. Ehrlich, M.D., of Baxter BioScience in Vienna, Austria, and colleagues analyzed data from 275 volunteers who were each given two doses of vaccine 21 days apart. Participants were randomized to receive formulations containing 3.75 μg, 7.5 μg, 15 μg or 30 μg of hemagglutinin antigen with alum adjuvant, or 7.5 μg or 15 μg without adjuvant.

The investigators found that the formulations without adjuvant resulted in the largest responses to the vaccine strain. The 7.5-μg formulation resulted in a 76.2 percent neutralizing-antibody response, or the equivalent to a 69 percent seroconversion rate. The vaccine created a response not just to the clade 1 strain, but also clade 2 and 3 strains. The most common adverse events for all formulations were mild injection site pain and headache.

"Our study provides initial safety and immunogenicity data for a whole-virus H5N1 vaccine produced on Vero cell culture. It also shows that a broadly reactive immune response to clade 2 and clade 3 of H5N1 virus can be obtained with the use of a low-dose clade 1 vaccine without adjuvant. Since we observed no significant dose-response relationship, the 7.5-μg formulation without adjuvant has been chosen for further development," the authors write.

The study was supported and designed by Baxter; Ehrlich and a number of co-authors are employees of the company.

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