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.