Women report more severe local and systemic reactions to influenza virus vaccines [100, 102, 104, [106] [107] [108] . Women also experience worse reactions to vaccine adjuvants [109] , which should be considered for 2009 H1N1 vaccines that are administered with adjuvant [88, 89] . The extent to which adverse reactions to the 2009 H1N1 vaccine differ in either frequency or severity between males and females has not been reported [60] .