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Objectives 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). Conclusion 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. CLINICAL TRIAL REGISTRATION NUMBER #NCT04754698

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