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The flu vaccine is a vaccine produced every year to protect against the highly variable Influenza virus.
Each year the influenza virus changes and different strains become dominant. Due to the high mutability of the virus a particular vaccine formulation usually only works for about a year. The World Health Organization co-ordinates the contents of the vaccine each year to contain the most likely strains of the virus to attack the next year. The flu vaccine is usually recommended for anyone in a high-risk group who would be likely to suffer complications from influenza.
The traditional injectable vaccine is grown in fertilized chicken eggs and the nasal spray, FluMist produced by MedImmune, is grown in chick kidney cells which makes both contraindicated for those with sensitivity to egg or chicken proteins.
The production of the vaccine requires a lead time of about six months before the season. It is possible that by flu season a strain becomes common for which the vaccine does not provide protection. In the 2003-2004 season the vaccine was produced to protect against A/Panama, A/New Caledonia, and B/Hong Kong. The strain A/Fujian was discovered after the vaccine was in production therefore did not provide protection against this strain.
On October 5, 2004, Chiron Corporation, a corporation contracted to deliver half of the expected flu vaccine for the United States and a significant portion to the UK, issued a press release [1] (http://www.chiron.com/investors/pressreleases/press_release100504.pdf) that stated it was unable to dispense its stock for the 2004-2005 season, due to suspension of the corporation's license to produce the vaccine by the Medicines and Healthcare Products Regulatory Agency. However, the Centers for Disease Control and Prevention took action to enlist the help of other companies such as Aventis Pasteur to supply the vaccine in high-risk populations in the United States.
Health Controversy
In the late 1990s, a controversy arose from the use of thimerosol, a preservative containing mercury, in vaccines. This preservative was proported to have a link to autism. However, the flu vaccine is not routinely administered to children under the age of 2, and all recent scientific evidence does not support a link between autism and vaccines.
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