ABSTRACT
OBJECTIVES: To assess immunogenicity of a heterologous 4th dose of a mRNA (BNT162b2) SARS-CoV-2 vaccine in autoimmune rheumatic diseases (ARD) patients with poor/non-response to inactivated vaccine (Sinovac-CoronaVac). METHODS: 164 ARD patients who were COVID-19 poor/non-responders (negative anti-SARS-CoV-2 S1/S2 IgG and/or neutralising antibodies-NAb) to the 3rd dose of Sinovac-CoronaVac received an additional heterologous dose of mRNA (BNT162b2) three months after last dose. IgG and NAb were evaluated before and after the 4th dose. RESULTS: Significant increases were observed after 4th dose in IgG (66.4% vs 95.1%, p< 0.001), NAb positivity (5.5% vs 83.5%, p< 0.001) and GMT (29.5 vs 215.8 AU/ml, p< 0.001), and 28 (17.1%) remained poor/non-responders. Patients with negative IgG after 4th dose were more frequently under rituximab (p= 0.001). Negative NAb was associated with older age (p= 0.015), rheumatoid arthritis (p= 0.002), systemic sclerosis (p= 0.026), leflunomide (p= 0.016), and rituximab use (p= 0.007). In multiple logistic regression analysis, prednisone dose ≥7.5 mg/day (OR = 0.34; p= 0.047), leflunomide (OR = 0.32, p= 0.036) and rituximab use (OR = 0.19, p= 0.022) were independently associated with negative NAb after the 4th vaccine dose. CONCLUSIONS: This is the largest study to provide evidence of a remarkable humoral response after the 4th dose of heterologous mRNA SARS-CoV-2 vaccination in ARD patients with poor/no-response to the 3rd dose of an inactivated vaccine. We further identified that treatment, particularly rituximab and prednisone, impaired antibody response to this additional dose. TRIAL REGISTRATION: ClinicalTrials.gov, https://clinicaltrials.gov, CoronavRheum #NCT04754698.