Seasonal influenza vaccination was used to assess whether induction of immunity as well as the rate of side effects is influenced by the timing of the last training session before vaccination. Healthy athletes were vaccinated with the tetravalent influenza vaccine and blood samples were collected before, 1, 2 and 26 weeks after vaccination. The athletes were randomly assigned to vaccination within 2 hours after the last training session ("2h") vs. vaccination after a resting period of at least 26 hours ("26h"). All participants documented side effects and training restrictions. Influenza-specific T-cells were quantified after stimulation with the vaccine based on intracellular cytokine staining. Antibodies were quantified by ELISA and neutralisation assay.

Inclusion Criteria:

• performance-oriented training on at least five days a week, healthy athletes

Exclusion Criteria:

• current acute infection, allergy to the vaccine, immunosuppression, pregnancy, rheumatic diseases