http://www.medscape.com/viewarticle...p_wir&uac=169258FZ&spon=17&impID=953908&faf=1 This section caught my eye... "Many individuals report discomfort and adverse events after vaccination that can include fatigue, nausea, and achiness. The researchers were surprised to find molecular evidence for the patient-reported phenomena of developing influenza symptoms after an influenza vaccination. Approximately one quarter of individuals in the human immune response dynamics cohort reported medium-high levels of such adverse events. Dr Sobolev and colleagues found that these individuals had a distinct gene expression profile that could be traced back to the presence of transitional B cells in the blood before vaccination. This small difference in the immune system thus appeared to underlie the generalized adverse effects described by some people when they receive a vaccination."