The annual flu shot is largely ineffective at preventing recipients from getting the flu and researchers believe they have now found out one reason why. A recent report in the journal PLOS Pathogens details how the process used to create the vaccines may be the crux of the problem.
The flu vaccine has been around for 70 years and it is made by injecting the flu virus into a chicken egg and allowing it to replicate. The fluid is then purified and combined with other ingredients to make the vaccine. However, scientists at The Scripps Research Institute have discovered that when the virus is injected into the egg it begins to mutate. By the time virus has completed its replication process and is ready to be included in the vaccines it no longer resembles the original strain of flu that was initially injected.
While there are multiple strains of the influenza virus, research for this study centered around the examination of the H3N2 virus because it is one of the most widespread and considered one of the most common causes of the seasonal flu.
Research Associate Dr. Nicholas Wu used high-resolution imaging in his examination. He was able through X-ray crystallography to see how the H3N2 subtype mutates a key protein to better attach to receptors in bird cells when grown in eggs.
This mutation affects a portion of the protein that is generally recognized by our immune system. As a result, the vaccine with the mutation is not able to trigger the effective immune response hoped for by the vaccine makers. This leaves the body unprotected from the original H3N2 strain.
Researchers believe current flu vaccines are only about 33 percent effective and that number appears to be trending downward. The issues raised in this study are causing scientists to look for alternative approaches to grow the virus in their quest to improve the efficacy of these vaccines.
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