Clinical Trial to Assess the Influenza Vaccination of the Hospitalized Adults

Inclusion Criteria: * Age ≥ 18 year * Affiliated with social security health insurance * Written informed consent * Patients hospitalized for at least 24 hours for one of the reasons indicated in Table 1 of protocol * Presence of Influenza-like syndrome before the hospitalization (even if symptoms are not present at the time of inclusion), or less than 48 hours after the hospitalization * Rapid completion of nasopharyngeal sample after hospitalization without exceeding 7 days after the onset of Influenza-like syndrome Exclusion Criteria: * Realization of nasopharyngeal sampling more than 7 days after the onset of symptoms * Contraindication for influenza vaccine (Hypersensitivity to the active substances, to any of the excipients and to trace eg eggs, including ovalbumin, chicken protein) * Patients institutionalized without regular community interaction * Previously tested positive for any influenza virus in the current season (RT-PCR, multiplex RT-PCR) * Patient under curatorship or under guardianship whose sample was obtained as part of their medical care but not complying with the conditions of Article L1121-8 of the Code de la Santé Publique. * Patient under curatorship or under guardianship whose sample was not obtained as part of their medical care.