Influenza constitutes a serious problem for healthcare and social services worldwide, owing to its pattern and the severity of its complications in some categories of subjects at risk, such as the elderly and immunocompromised individuals. The only really effective means of combating influenza is vaccination. The elderly and immunocompromised subjects are refractory or low responders to vaccination. The need for ever more immunogenic and efficacious influenza vaccines, especially for subjects at risk, has prompted the development of adjuvated vaccines. With a view to enhancing the immune response in the elderly and in subjects at risk, the possibility of co-administering immunostimulants as Thymosin ?-1 (T?1) with influenza vaccines has been investigated. T?1 is a biologically active peptide made up of 28 amino acids that can enhance T-cells, dendritic cell and antibody responses, modulate cytokines and chemokines production. Several studies were conducted and showed that T?1 ameliorate the performance of influenza vaccination in elderly and subjects at risk. Although further studies on co-adjuvants are necessary, the future prospects of producing ever more efficacious influenza vaccines appear very promising.