New flu codes are for the exact antigen you are using. Per Medicare as of Jan 1, 2011 new flu codes are as follows:
Q2035 Afluria "influenza virus vaccine, split virus, when administered to individuals 3 years of age or older, for intramuscular use"
Q2036 Flulaval "influenza virus vaccine, split virus, when administered to individuals 3 years of age or older, for intramuscular use"
Q2037 Fluvinin "influenza virus vaccine, split virus, when administered to individuals 3 years of age or older, for intramuscular use"
Q2038 Fluzone "influenza virus vaccine, split virus, when administered to individuals 3 years of age or older, for intramuscular use"
Q2039 "influenza virus vaccine, split virus, when administered to individuals 3 years of age or older, for intramuscular use" NOT OTHERWISE SPECIFIED