Live,+Attenuated+Vaccines

   **Classical Reassortment:**  Here, the 'wild type' influenza virus must be crossed with a compatible 'carrier' virus. This carrier virus is much less virulent than the wild type virus, so the hybrid virus will not cause a bad infection. In order to create attenuated vaccine like this, the HA and NA of the wild type virus must be transferred and the other 6 genome segments of the carrier virus must be contained in the new 'hybrid' virion.

The 'wild type' and 'carrier' virus are placed inside a fertilised chicken egg and then they are able to swap genome segments and mutate.

In order to then collect the virions with the correct genetic makeup, they are separated, usually through the use of a centrifuge (Robertson et al. 2011, p 1837).



 ** Reverse Genetics: **  This process which produces a virus with predefined genetic characteristics. This method relies on seperating the HA and NA genes from the 'wild type' virus and transporting into a cell culture. Once the antigenic HA and NA genes have been removed, they are combined with the other 6 segments from a carrier virus. Using this approach the resulting genetic combination is highly predictable.(Robertson et al. 2011, p 1837).