Flu Vaccine #2
Traditional influenza vaccine is manufactured using three potentially threatening strains of flu (as designated by WHO). In the graphic these are shown as blue, red and purple virions. The green virion represents a standard strain that grows easily in chicken eggs.
The fate of the purple strain is shown in more detail (although the same process is happening in parallel with all three epidemic strains). The purple and green viruses are cultured together in eggs to create a reassortant (shown as small purple particles). This vaccine strain is then grown in millions of eggs. The vast amount of virus produced is illustrated as an array of purple particles emerging from the bottom layer of eggs. This latter process is shown for each of the selected wild strains (blue and red particle arrays). Ultimately, these three vaccine strains are treated to make them inactive (basically smashed up) and form the new (trivalent) inactivated flu vaccine for that year. This is a killed virus vaccine. A similar process is used to create a live virus vaccine but in this case the standard virus would be one that is weakened (attenuated) and grows at lower temperatures.