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Mixed MessageOn Bird-Flu Vaccine
posted by admin on 03/04/06
Effectiveness Is Only in High Doses, Posing Production Difficulty
An experimental bird-flu vaccine under development by the U.S. government and Sanofi-Aventis SA is effective only at high doses, making it difficult to mass-produce in the event of a pandemic, according to a new study.
The findings provided a mixed message of hope for an answer to the deadly disease, but only if manufacturing ramps up ahead of any widespread contagion. Production of avian-influenza vaccines is restricted by the limited capacity of vaccine makers and the fact that the virus particles used to develop the vaccine have to be grown in fertilized hen eggs.
"This is more of a clear indication that we have a way to go," said Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases, in an interview. "This is not the answer in and of itself." Dr. Fauci's agency is spearheading the government research on bird flu.
The study published in this week's New England Journal of Medicine found the vaccine from Sanofi Pasteur, a unit of Paris-based Sanofi-Aventis, was only effective at six times the standard dose. In addition, two doses were needed to get the best result -- and even then it only produced the desired immune response in 54% of the patients tested. The study detected no significant side effects associated with the vaccine.
"Given that this is a new kind of influenza virus for the body to experience, we anticipated it would take more of a punch to elicit an immune response, and that is certainly the case," said William Schaffner, chairman of the department of preventive medicine at Vanderbilt University School of Medicine who served on the safety-monitoring board for the study. "What we learned is it takes a lot more. We anticipated a better response at the low dose."
Dr. Fauci said researchers are turning their attention to figuring out ways to get more of a reaction from the vaccine to reduce the need for huge quantities of it. One method being studied is to add immune-system boosters, known as "adjuvants," to produce a stronger reaction from lower doses of the bird-flu vaccine. Among the adjuvants being studied are aluminum, which is already used in other vaccines, and another substance known as MF59.
Sanofi Pasteur, in a statement, said it is boosting its production capabilities by building a plant in Swiftwater, Pa., that will double its U.S. capacity by 2009, and expanding its facility in Val de Reuil, France. The current world-wide manufacturing capacity is estimated to be such that it can only produce enough vaccine for 75 million people, according to an accompanying editorial in the NEJM.
U.S. health agencies have awarded contracts to Sanofi and Chiron Corp., of Emeryville, Calif., to produce and test vaccines to protect against the H5N1 virus, which has proved to be the deadliest of the 16 subtypes of avian-influenza viruses. There are no approved vaccines for the virus.
The U.S. government has stockpiled enough bulk concentrate of the bird-flu vaccine to immunize 3.8 million people, which is well short of the goal of 20 million set by health officials. The two companies have also produced thousands of experimental doses for clinical trials.
The H5N1 virus was first detected in Hong Kong in 1997. The virus is spread by birds and has continued to move into Europe and Africa from Asia.
Write to David Armstrong at email@example.com
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