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Objectives To assess the levels of IgG response after the second dose of SARS-CoV-2 vaccination in Thai SLE patients compared with healthy controls, and to explore factors associated with low immunogenicity to SARS-CoV-2 vaccine.Methods In this cross-sectional case-control study, adult Thai SLE patients and age- and sex-matched healthy controls were enrolled following two SARS-CoV-2 vaccine doses under the Thai national immunization program. SARS-CoV-2 spike protein IgG was measured using electro-chemiluminescence immunoassay. Low immunogenicity was defined as IgG <15 U/mL.Results Among 92 SLE patients and 41 controls, IgG levels were not significantly different (median: 221.3 vs. 196.8 U/mL, p=0.41). The mRNA and viral vector vaccines yielded higher antibody levels than inactivated vaccines in SLE patients. Factors such as active lupus nephritis and moderate-to-high dose corticosteroid use appeared to be associated with lower IgG responses, though not statistically significant.Conclusions Thai SLE patients demonstrated an immune response comparable to that of healthy controls. A stronger immune response was observed in SLE patients who received viral vector and mRNA vaccines, compared to those who received inactivated vaccines. Both vaccine type and disease-related factors may influence the magnitude of the immune response, emphasizing the need for tailored vaccination strategies in this population.