In a double-blind phase 3 clinical trial, a vero-cell-cultured-derived trivalent influenza vaccine was found to provide a similar level of protection as the egg-based influenza vaccines currently in use. During the 08-09 flu season, half were assigned to receive the vaccine in trial and the other half were assigned to receive the placebo among 7250 participants. They found the efficacy of the vaccine to be about 78.5% and found no serious side effects from the vaccine. To test the efficacy, the analysis was based on intention to treat.
If this vaccine further proves to be as efficacious as the egg-based vaccine, this will give an edge to humans in the war against the influenza virus. Because the egg-based vaccine takes about 6 months to prepare, scientists have to make predictions as early as possible. Since the strain for the next year's flu epidemic tends to surface at the end of the current year's flu season, scientists base their predictions on this latest strain. However, waiting until the end of the epidemic is not a feasible option because the vaccines need to be in production earlier. Therefore, if the cell-culture derived vaccine, which will be manufactured more efficiently and quickly, is proven to provide similar levels of protection as the egg-based vaccine, we can make more reliable predictions regarding the new strain that will surface in next year's epidemic.