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As vaccine-makers gear up for the winter flu season, one biotech company is reporting success with an alternative method of developing a flu preventative that it says could work more effectively and be produced more quickly than traditional inoculations prepared in fertilized chicken eggs.
This moves Rockville, Md.–based Novavax, Inc., a step closer to submitting its seasonal flu vaccine candidate to the U.S. Food and Drug Administration (FDA) for approval, and at the same time helping the company move forward with its efforts to develop a vaccine against the H1N1 "swine" flu. The company's vaccine approach in both cases is to use viruslike particles (VLPs) containing surface proteins that make the VLPs resemble a virus, thereby eliciting the proper immune response—even though the VLPs lack the genes needed to replicate themselves.
To prepare a vaccine made in fertilized chicken eggs, scientists crack the shell and inject the influenza virus into the fluid surrounding the embryo. Ideally, the embryo is infected and the virus multiplies. After several days of incubation the eggs are opened and the virus is removed, purified and used to make the vaccine, as a 2004 Scientific American article points out. (The VLP approach bypasses the steps needed to adapt virus strains to grow in eggs.)
There are, however, several drawbacks to this "chicken and egg" approach, which dates back more than 50 years. In order to produce 300 million doses of vaccine, egg-based production would require some 900 million eggs, according to the U.S. Department of Health and Human Services. An outbreak of avian flu in particular could put eggs in short supply, restricting the amount of vaccine that could be produced. In addition, vaccine-makers that use eggs cannot begin developing new vaccines that target new virus strains until the U.S. Centers for Disease Control and Prevention (CDC) creates a live-virus reference strain for these companies to work with, a process that could take several weeks.
Novavax says it can develop a prototype vaccine without the aid of a virus reference strain. Instead, it uses information the CDC posts in the Global Initiative on Sharing Avian Influenza Data (GISAID) database, launched in 2006 by a number of science institutes and universities worldwide (including WHO, the CDC and the Max Planck Institute for Informatics) to encourage data-sharing in response to the global spread of the H5N1 avian flu. The company claims its VLP approach allows it to manufacture a vaccine to match a particular virus strain in about three months.
Novavax says that during Phase IIa of seasonal flu vaccine testing, which began in May, it was able in the majority of people tested to surpass the FDA's requirements for producing enough antibodies to protect the body from the H3N2, H1N1 and B viruses—all of which were common enough a year ago to be used to develop flu vaccines for the 2008 to 2009 flu season. The vaccine was most effective against H3N2, increasing antibody titers (a measure how much antibody is produced after vaccination) fourfold in more than 81 percent of who received it, according to the company.