WebMD
Is the swine flu vaccine brand new? Yes and no. The 2009 H1N1 swine flu vaccine is made exactly the same way as the seasonal flu vaccine, by the same manufacturers using the same materials — except for one shiny new piece.
What has changed is the piece of the virus the vaccine uses to prime the immune system.
Vaccine experts tell WebMD this change isn’t all that new. Every couple of years or so, a new variant of a seasonal flu virus comes along. When that happens, a “new” vaccine is made using the relevant part of the variant virus.