Influenza vaccine

The flu vaccine is a vaccine produced every year to protect agains 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.

Due to contamination concerns, one of the primary vaccine producers was unable to dispense its stock for the 2004-2005 season, leading to severe shortages in the US and UK