The aims of the study are to a) identify individuals with a poor response to influenza vaccination and b) identify factors associated with a poor response to influenza vaccination.

This is a population-based prospective cohort study. Potential participants, males and females between 65 and 80 years of age, were selected randomly through the resident registration office in Hannover city, Germany and invited with a personalized letter to participate in the study.

Initially, a blood sample (40 ml) will be drawn from each participant (day 0). Furthermore, participants will be vaccinated against influenza with FLUAD 2014/2015. FLUAD is a trivalent, surface antigen, inactivated influenza virus vaccine adjuvanted with MF59C.1. Additional five blood samples will be collected during the study period of four months (at days 3, 7, 21, 70 and 130). Information about current and past infections, chronic diseases and basic sociodemographic data will be collected through a self-administered questionnaire.

Inclusion Criteria:

• Individuals between 65 and 80 years of age

Exclusion Criteria:

• Individuals with a known hypersensitivity to any of the excipients and to eggs, chicken Protein, kanamycin and neomycin sulphate, formaldehyde, and cetyltrimethylammonium bromide
• Individuals, who have an acute infection during the visit at the study Center
• Individuals with cognitive impairment
• Individuals already vaccinated with influenza vaccination in the influenza season 2014/15

Males and females aged 65 and 80 years from the general population