Clinical Trial Evaluating Efficacy and Safety of One Dose Versus Two Doses of Influenza Vaccination

"Patients will be randomized at 1:1 rate and open label fashion, according to centers, and time elapsed since transplant and type of organ transplanted to one of this two interventions :~A arm (usual treatment): Influenza vaccine (split virion, inactivated) suspension for injection 0.5ml at the baseline.~B arm (experimental branch): Influenza vaccine (split virion, inactivated) suspension for injection 0.5ml at the baseline and 5 weeks after the first dose.~The follow-up of both arms will be at 5, 10 and 15 weeks and one year after the baseline."