Understanding The Flu Vaccine

David P. Calfee, MD, Infection Control Officer, The Mount Sinai Medical Center, recently discussed the flu vaccine: -- What is the seasonal flu shot? The seasonal flu shot is given annually and protects against three common viruses, one influenza A (H3N2) virus, one regular seasonal influenza A (H1N1) virus not the pandemic 2009 H1N1 virus and one influenza B virus.