Antibody response to BNT162b2 SARS-CoV-2 mRNA vaccine in adult patients with systemic sclerosis

Objectives: Systemic sclerosis (SSc) patients are at risk for a severe disease course during SARS-CoV-2 infection either due to comorbidities or immunosuppression. The availability of SARS-CoV-2 vaccines is crucial for the prevention of this hard-to-treat illness. The aim of this study is to assess the humoral response after mRNA vaccination against SARS-CoV-2 in SSc patients. Method: Seropositivity rate and serum IgG levels were evaluated 1 month (t1) and 3 months (t3) after the second dose of vaccine in a cohort of SSc patients and healthy controls (HC). Differences were made with Student's or Mann-Whitney's t-test and with the chi-square or Fisher exact test. Logistic regression model including immunosuppressive treatments (corticosteroids, CCS; mycophenolate mofetil, MMF; methotrexate, MTX; rituximab, RTX) was built to assess the predictivity for seropositivity. Results: The seropositivity rate was similar in 78 SSc patients compared to 35 HC at t1 but lower at t3. SSc patients had lower serum IgG levels than HC at t1 but not at t3. SSc patients treated with immunosuppressive therapy showed both a lower seropositive rate (t1, 90.3% vs 100%; t3, 87.1% vs 97.9%; p < 0.05) and serum IgG levels than untreated patients both at t1 [851 BAU/ml (IQR 294-1950) vs 1930 BAU/ml (IQR 1420-3020); p < 0.001] and t3 [266 BAU/ml (IQR 91.7-597) vs 706 BAU/ml (IQR 455-1330); p < 0.001]. In logistic regression analysis, only MTX was significant [OR 39.912 (95% CI 1.772-898.728); p < 0.05]. Conclusions: SSc patients treated with MTX had a lower serological response to mRNA vaccine, and even low doses of CCS can adversely affect antibody titer and vaccination response. Key Points • SSc patients are able to produce vaccine-induced antibodies after mRNA vaccination. • In SSc patients, clinical characteristics of disease did not influence seropositivity rate. • In SSc patients, even low doses of CCS can adversely affect antibody titer and vaccination response. • In SSc patients, MTX treatment is mainly associated with reduced seropositivity and lower serum IgG levels.