A flu virus contains eight gene segments. One of the gene segments codes for the surface antigen hemagglutinin (HA), and another codes for the surface antigen neuraminidase (NA). Each year, researchers predict which flu strains will be most prevalent and select three—two influenza A strains and an influenza B strain—to be included in that year’s vaccine.
The goal of reassortment is to combine the desired HA and NA antigens from the target strain (flu strain 1) with genes from a harmless strain that grows well in an egg (flu strain 2).
The illustration details the following steps in creating the vaccine:
Credit: This image is in the public domain. Please credit the National Institute of Allergy and Infectious Diseases (NIAID). Illustrator: Links Studio. Download: high resolution version of Reassortment illustration
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Last Updated January 14, 2011