It's easiest to just go straight to the source for this info: http://www.cdc.gov/flu/professionals/vaccination/vaccine_safety.htm http://www.cdc.gov/flu/profess

It's easiest to just go straight to the source for this info: http://www.cdc.gov/flu/professionals/vaccination/vaccine_safety.htm http://www.cdc.gov/flu/professionals/vaccination/vaccine_saf... The two key points: 1. "The most frequent reactions reported after vaccination in children and adults are pain and other injection-site reactions. Up to 64% of people vaccinated with IIV experience pain at the injection site, which usually resolves in <2 days without treatment." 2. "Fever, malaise, myalgia, and other systemic symptoms that can occur after vaccination with IIV most often affect persons who have had no previous exposure to the influenza virus antigens in the vaccine (e.g., young children). In adults the rate of having these events is similar after IIV and after a placebo injection." So other than your arm aching for <2 days where injected, the 'symptoms' are no more common than a placebo injection.