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Autoimmune myasthenia gravis is a T helper cell (Th)-dependent autoimmune disease. Autoantibodies directed against the acetylcholine receptor (anti-AChR-Ab) cause muscle weakness with improvement of symptoms with regeneration. Changes in anti- AChR-Ab titers correlate intra-individually with the severity of symptoms. In most cases immunosuppressive treatment and anticholinesterase drugs can control this medical condition well. The Standing Committee on Vaccination at the Robert Koch Institute (STIKO) recommends seasonal influenza vaccination for people with chronic diseases or over the age of 60. Especially neurologic disorders are included since an update of the recommenda- tions in 2010. Prospective studies about influenza vaccination in MG are lacking. Additionally there is neither evidence about the concern of boostering of anti-AChR-Abs by influenza vaccination nor reduced vaccine protection due to immunosuppressive treatment. In our study 62 anti-AChR-Ab-positive patients were randomized to get intramuscular injection of seasonal influenza vaccination (Mutagrip®) or placebo (0.9% NaCl- Solution). Immunosuppressive treatment “yes or no” was considered by balanced rand- omization. Clinical and serologic parameters were determined at baseline and 3 and 12 weeks afterwards (V1, V3, V5). Primary endpoint was the relative change of anti- AChR-Ab-titer at week 12 compared to baseline values. Secondary endpoints were: clinical change assessed by a modified MG-score (mBS), increase of anti-influenza- ELISA-antibodies (Influenza A/B IgA and IgG) three weeks after immunization and changes of immunsuppressive or anticholinesterase treatment. There were no significant differences in AChR-Ab-titer change between the two groups. A decrease of median titers was found in both groups (6,0 % in vaccine group, 2.8 % in placebo group). Changes in mBS between the groups showed no significant differences either. Adverse events did not happen more often in the vaccine group. One serious adverse event occurred which was not related to vaccination. We found significant influenza-ab increase only for Influenza A IgA and Influenza B IgG in the vaccine group. Only one patient achieved a fourfold ab-increase (seroconversion). ￼Our study demonstrates that seasonal influenza vaccination in MG-patients is safe. Because of the low influenza antibody response further investigation concerning vaccine effectiveness and effiacy and changes in vaccine strategy is needed.