Factors associated with disease flare following SARS-CoV-2 vaccination in people with inflammatory rheumatic and musculoskeletal diseases: results from the physician-reported EULAR Coronavirus Vaccine (COVAX) Registry.

Objectives: To investigate the frequency and factors associated with disease flare following vaccination against SARS-CoV-2 in people with inflammatory/autoimmune rheumatic and musculoskeletal diseases (I-RMDs).

Methods: Data from the European Alliance of Associations for Rheumatology Coronavirus Vaccine physician-reported registry were used. Factors associated with flare in patients with I-RMDs were investigated using multivariable logistic regression adjusted for demographic and clinical factors.

Results: The study included 7336 patients with I-RMD, with 272 of 7336 (3.7%) experiencing flares and 121 of 7336 (1.6%) experiencing flares requiring starting a new medication or increasing the dosage of an existing medication. Factors independently associated with increased odds of flare were: female sex (OR=1.40, 95% CI=1.05 to 1.87), active disease at the time of vaccination (low disease activity (LDA), OR=1.45, 95% CI=1.08 to 1.94; moderate/high disease activity (M/HDA), OR=1.37, 95% CI=0.97 to 1.95; vs remission), and cessation/reduction of antirheumatic medication before or after vaccination (OR=4.76, 95% CI=3.44 to 6.58); factors associated with decreased odds of flare were: higher age (OR=0.90, 95% CI=0.83 to 0.98), non-Pfizer/AstraZeneca/Moderna vaccines (OR=0.10, 95% CI=0.01 to 0.74; vs Pfizer), and exposure to methotrexate (OR=0.57, 95% CI=0.37 to 0.90), tumour necrosis factor inhibitors (OR=0.55, 95% CI=0.36 to 0.85) or rituximab (OR=0.27, 95% CI=0.11 to 0.66), versus no antirheumatic treatment. In a multivariable model using new medication or dosage increase due to flare as the dependent variable, only the following independent associations were observed: active disease (LDA, OR=1.47, 95% CI=0.94 to 2.29; M/HDA, OR=3.08, 95% CI=1.91 to 4.97; vs remission), cessation/reduction of antirheumatic medication before or after vaccination (OR=2.24, 95% CI=1.33 to 3.78), and exposure to methotrexate (OR=0.48, 95% CI=0.26 to 0.89) or rituximab (OR=0.10, 95% CI=0.01 to 0.77), versus no antirheumatic treatment.

Conclusion: I-RMD flares following SARS-CoV-2 vaccination were uncommon. Factors associated with flares were identified, namely higher disease activity and cessation/reduction of antirheumatic medications before or after vaccination.