Influenza is a common respiratory virus that is categorized into four types: A, B, C and D. Type C only causes mild infections and type D is not believed to infect humans. However, influenza A and ...

The 1976 'swine flu' shot has been linked to stronger immune ... enhanced immune response against both the 2009 pandemic H1N1 virus and a different H1N1 flu strain that circulated during the ...