POS0543 DETECTION OF SARS COV-2 ANTIBODIES FOLLOWING VACCINATION IN PATIENTS WITH RHEUMATIC MUSCULOSKELETAL DISEASE (DECODIR) – A REPORT FROM A DANISH PROSPECTIVE COHORT STUDY

Background The COVID-19 pandemic caused concerns whether patients with rheumatic musculoskeletal disease (RMD) treated with conventional (cs) or biologic (b) disease modifying drugs (DMARDs) and/or prednisolone exhibit an adequate immune response to the applied SARS-CoV2 vaccines.

Objectives We established the DECODIR study to assess and compare the efficacy of the SARS-CoV2 vaccines administered as part of the national vaccine roll-out: BNT162b2 vaccine (Pfizer/BioNTech) and mRNA-1273 vaccine (Moderna). The vaccines were offered as two doses four weeks apart; followed by a booster vaccination six months later. This national regimen included inflammatory rheumatic patients regardless of their respective anti-inflammatory treatment. We used patients’ SARS-CoV2 IgG serum level as proxy for vaccination response (1).

Methods The study was conducted as a longitudinal prospective cohort study. Patients with rheumatoid arthritis (RA), spondyloarthropathies (SpA) or psoriatic arthritis (PsA) receiving their outpatient treatment at the Danish Hospital for Rheumatic Diseases, Sonderborg, and monitored in the Danish DANBIO registry, were included.

Blood samples, Disease activity and treatment information (cs/bDMARD, prednisolone) were collected at baseline (i.e. prior to vaccination), after six weeks, six and twelve months. SARS-CoV-2 IgG levels in serum were assessed by ELISA (Thermo-Fischer), and manufacturer’s cut-off (>=10 EliA U/mL) selected as definition of sufficient IgG response. Antibody response was measured and compared at all four time points.

Associations between antibody response, age, gender, disease (RA/PsA/SpA), treatment (none, cs/bDMARD or prednisolone) and disease activity were tested using proportional odds regression and bootstrapped tests of medians. Results were reported using mean, median (IqR) and bootstrapped 95% confidence interval (CI) of the median.

Results A total of 243 patients were included at baseline and all were followed-up after six weeks; data from 233 patients were available at six months and for 229 patients at twelve months’ follow-up. Those 229 patients had completed the national vaccination programme.

The measurements performed 6 months after baseline demonstrated a per se decrease of IgG levels for the whole study population (median of 2.08 EliA U/mL at 6 months vs. 16 EliA U/mL at 6 weeks). The final measurements performed after twelve months demonstrated a significant increase of IgG levels. Thus, the completed vaccination programme, was followed by a significant increase in IgG levels (median of 100 EliA U/mL at twelve months vs. 16.5 EliA U/mL at six months, p < 0.001).

Sufficient response rates were now recorded in all treatment scenarios, also in patients treated with prednisolone or combination of csDMARD and bDMARD. These two groups were at 6 months characterized by significant lower response rates, when compared with patients without any DMARD treatment.

Conclusion Completed vaccination programme defined as two doses plus booster vaccination resulted in a sufficient vaccination response as measured by IgG levels regardless of RA treatment.

It is noteworthy that IgG levels increased markedly in patients treated with a combination of cs/bDMARD or oral prednisolone, who had low IgG levels (below manufacturer’s cut-off >=10 EliA U/mL) after 6 months. Our results strongly support the efficacy of the complete vaccination programme including the 3rd booster vaccine in patients with inflammatory rheumatic diseases.