Background/Purpose: In the begining of pandemic and till spring 2021 there were no clinical and laboratory data regarding sefety and efficacy of mRNA vaccines against Covid 19 in patients (pts) with systemic sclerosis (SSc), particularly treated with DMARDs (conventional [cs] and biological [bDMARD]). Our aims were to assess the humoral response to 2 doses of mRNA vaccine against Covid 19 and the impact of vaccination on SSc disease features in pts treated with DMARDs.

Methods: Consecutive SSc pts treated at our rheumatology institute who received their 1^st SARS-CoV-2 (Pfizer) vaccine were recruited to the study and reassessed 4-6 weeks, 24-28 weeks after the 2^nd dose of vaccine and the 3^rd dose of vaccine (“booster”). Pts were assessed for SSc manifestations and activity, data on vaccine side effects and actual therapy, and blood samples were obtained for serology test at each three visit. Neutralizing IgG Antibodies (Ab) against the spike receptor-binding domain of SARS COV2 virus were detected using the SARS-Cov-2 IgG II Quant (Abbott) assay (positive >50AU/ml).

Results: Fifty seven SSc pts (mean age [SD] 58.5 [12.3]), disease duration 9.6 [6] years; 51 (89.5%) female; 28 (49.1%) diffuse SSc; 13 (22.8%) had Overlap with other connective tissue diseases). Thirty-six pts (63%) received csDMARDs (19 [33%] were on mycophenolate mofetil [MMF]), 16 (28%) received bDMARDs (7 pts recieved rituximab, RTX), 6 (10%) – csDMARDs and bDMARDs combination, and 18 (32%) – steroids. Forty-five (79%) pts developed significant humoral response (mean [SD] 7717.6 AU/ml [10148.6], median [IQR] 3045 [170-40000] AU/ml). Among 12 pts without humoral response 4 pts received MMF; 4 – MMF combined with abatacept (2 pts) or with RTX (3 pts), and 2 with RTX only. Humoral response was re-evaluated 24-26 weeks after the 2^nd vaccine in 22 out of 45 “seropositive” pts. The level of neutralizing IgG antibodies significantly declined from mean [SD] 5977.2 [8059] AU/ml to to mean [SD] )782.2 [938] AU/ml, from median [IQR] 2506 AU/ml to median 418 AU/ml respectively (p=0.005). Five pts with a previous negative humoral response received “booster” vaccine 24 weeks after the 2^nd dose of vaccine with a substantial raise of the neutralizing IgG antibodies titer 4 weeks afterwards (mean [SD] 13518.7 to 16294.3 AU/ml and median 3799 to 26946 AU/ml respectively, p=0.003). “Seronegative” RTX treated patient, remained negative despite the booster vaccine. Low grade fever and injection site reactions were reported in third of patients. The rheumatic disease remained stable in all SSc pts.

Conclusion: The vast majority of SSc pts developed a significant humoral response to 2 doses of the Pfizer mRNA vaccine against Covid-19. A significant decline of the humoral response was noted 24 weeks afterwards. “Booster” vaccine was effective in 50% of “seronegative pts but not in RTX treated pts. Only minor side effects and no apparent impact on SSc activity was noted.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/bnt162b2-mrna-vaccine-against-covid-19-humoral-response-safety-and-efficacy-in-scleroderma-patients/