Aim: To investigate the association between physical activity and immunogenicity among SARS-CoV-2 seropositive patients with autoimmune rheumatic diseases prior to and following a 2-dose schedule of CoronaVac (Sinovac inactivated vaccine). Methods: This was a prospective cohort study within an open-label, single-arm, phase 4 vaccination trial conducted in Sao Paulo, Brazil. In this substudy, only SARS-CoV-2 seropositive patients were included. Immunogenicity was assessed by seroconversion rates of total anti-SARS-CoV-2 S1/S2 immunoglobulin G (IgG), geometric mean titers of anti-S1/S2 IgG, frequency of positive neutralizing antibodies, and neutralizing activity before and after vaccination. Physical activity was assessed through a questionnaire. Model-based analyses were performed controlling for age (<60 or ≥60 y), sex, body mass index (<25, 25–30, and >30 kg/m²), and use of prednisone, immunosuppressants, and biologics. Results: A total of 180 seropositive autoimmune rheumatic disease patients were included. There was no association between physical activity and immunogenicity before and after vaccination. Conclusions: This study suggests that the positive association between physical activity and greater antibody responses seen in immunocompromised individuals following vaccination is overridden by previous SARS-CoV-2 infection, and does not extend to natural immunity.