Real-world immune response to SARS-CoV-2 vaccination in Thai patients with systemic lupus erythematosus: a cross-sectional observational study

Background Immunogenicity to SARS-CoV-2 vaccination in patients with SLE varies by vaccine type and immune-modulating therapy. However, data in Southeast Asian populations, especially among Thai patients with SLE, remain limited. Objective To assess the levels of IgG response after the second dose of SARS-CoV-2 vaccination in Thai patients with SLE 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 patients with SLE and age-matched and sex-matched healthy controls were enrolled following two SARS-CoV-2 vaccine doses under the Thai national immunisation programme. SARS-CoV-2 spike protein IgG was measured using electro-chemiluminescence immunoassay. Low immunogenicity was defined as IgG<15 U/mL. Results Among 92 patients with SLE and 41 controls, IgG levels were not significantly different (median: 221.3 vs 196.8 U/mL, p=0.41). The messenger RNA (mRNA) and viral vector vaccines yielded higher antibody levels than inactivated vaccines in patients with SLE. 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 patients with SLE demonstrated an immune response comparable to that of healthy controls. A stronger immune response was observed in patients with SLE who received viral vector and mRNA vaccines, compared with those who received inactivated vaccines. Both vaccine type and disease-related factors may influence the magnitude of the immune response, emphasising the need for tailored vaccination strategies in this population.