objective: To evaluate immunogenicity and safety of an inactivated SARS-CoV-2 vaccine in systemic autoimmune myopathies (SAMs) and the possible influence of baseline disease parameters, comorbidities, and therapy on immune response. methods: This prospective controlled study included 53 patients with SAMs and 106 non-immunocompromised control group (CTRL). All participants received two doses of the Sinovac-CoronaVac vaccine (28-day interval). Immunogenicity was assessed by anti-SARS-CoV-2 S1/S2 IgG seroconversion (SC), anti-S1/S2 IgG geometric mean titer (GMT), factor increase GMT (FI-GMT), neutralizing antibodies (NAb) positivity, and median neutralizing activity after each vaccine dose (D0 and D28) and six weeks after the second dose (D69). Participants with pre-vaccination positive IgG serology and/or NAb and those with RT-PCR confirmed COVID-19 during the protocol were excluded from immunogenicity analysis. results: Patients and CTRL had comparable sex (P>0.99) and age (P=0.90). Immunogenicity of 37 patients and 79 CTRL naïve participants revealed at D69, a moderate but significantly lower SC (64.9% vs. 91.1%, P<0.001), GMT [7.9 (95%CI 4.7-13.2) vs. 24.7 (95%CI 30.0-30.5) UA/mL, P<0.001] and frequency of NAb (51.4% vs. 77.2%, P<0.001) in SAMs compared to CTRL. Median neutralizing activity was comparable in both groups [57.2% (IQR 43.4-83.4) vs. 63.0% (IQR 40.3-80.7), P=0.808]. Immunosuppressives were less frequently used among NAb+ patients vs. NAb- patients (73.7% vs. 100%, P=0.046). Type of SAMs, disease status, other drugs or comorbidities did not influence immunogenicity. Vaccine-related adverse events were mild with similar frequencies in patients and CTRL (P>0.05). conclusions: Sinovac-CoronaVac is safe and has a moderate short-term immunogenicity in SAMs, but reduced compared to CTRL. We further identified that immunosuppression is associated with diminished NAb positivity. background: #NCT04754698.