Vaccine Design
Flu vaccines are made by creating altered forms of the flu virus that do not infect humans. These altered forms are injected into the human body where they will be detected by the immune system. The immune system will then get sensitized to the altered virus which, if designed correctly, will then also ready the immune system if the infectious virus is encountered. The vaccine is made from a flu virus that has either been killed, broken down or has been genetically modified so that it cannot cause the flu. The modified viruses must be similar enough to the original flu virus so that the immune system can be prepared to attack the original virus.
Allelic Drift
Each year a new version of the seasonal flu vaccine is created. This is because over time the flu virus changes (a procedure known as allelic drift or genetic drift), which means that a vaccine made the year before may not be effective for the new virus. As a result, scientists each year analyze the strains of flu going around and look for changes. They then use reverse genetic technology to apply these new changes into the existing flu vaccine, or make a whole new vaccine. This is done to ensure that the flu vaccine each year is effective against new strains of the flu.
Vaccine Production
Typically, the flu vaccine is made and replicated in other animals. Most of the time the virus is made in chicken egg embryos, where the vaccine is in an ideal environment to grow and replicate. These chicken eggs come from specially certified farms with strict veterinary control. Once the virus has replicated in the eggs, scientists then isolate it and package it into carefully measured doses that can then be shipped out to health clinics and physicians for administration to patients.
