 Metabolic syndrome MetS is a cluster of metabolic conditions associated with obesity that predispose individuals to coronary heart diseases and diabetes but obesity has been shown to increase the risks of other diseases like cancer and asthma. Studies have also shown that obesity increases the risk of severe influenza infection and associated death and reduces the efficacy of influenza vaccine in the obese population but yet, the molecular mechanisms have not been described. The investigators are thus hypothesizing that differences in the innate immune responses between individual with or without metabolic syndrome impact viral infection and vaccine outcome. The investigators will perform seasonal influenza vaccination in people with or without metabolic syndrome to determine if the late adaptive response assessed by antibodies titers is different between the two groups and correlates with the early immune response assessed by gene expression profile in whole blood cells. The project proposed by the investigators will contribute to a better understanding of the inflammatory phenotype associated with metabolic syndrome and establish for the first time if it affects the immune protection against infectious diseases and particularly against influenza virus infection. The results will be important to determine if the population affected by metabolic syndrome should receive anti-influenza treatment in priority in the context of a severe influenza epidemic. 