AB1353 SAFETY OF UPDATED XBB.1.5 SARS-CoV-2 VACCINE BOOSTERS IN PATIENTS WITH INFLAMMATORY JOINT DISEASES ON IMMUNOSUPPRESSIVE THERAPIES

Background: Patients with inflammatory joint diseases on immunosuppressive therapies are vulnerable to severe COVID-19 and are recommended to receive targeted vaccine boosters. Since these patients were excluded from phase 3 vaccine trials, it is important to evaluate safety of the updated XBB.1.5 vaccine as a 3rd booster dose in this patient group. Knowledge on the frequency of vaccine side effects is also helpful to inform patients and alleviate vaccine hesitancy. Objectives: To compare the safety of a booster dose with the updated monovalent XBB.1.5 vaccine to that of the previous bivalent vaccine type (BA.1/BA.4/5). Methods: The present analyses included patients with inflammatory joint diseases participating in the observational prospective Nor-vaC study [1,2], who received six vaccine doses while using immunosuppressive therapies. Patients received vaccines according to the national Norwegian vaccination program. After primary vaccination with three doses and a first booster dose, the further 2nd booster was bivalent (BA.1/BA.4/5) and the 3rd booster was monovalent (XBB.1.5). Data on adverse events within two weeks from vaccination were self-reported through questionnaires. The safety data following the 2nd bivalent and the 3rd monovalent booster were compared with Fisher's exact test. Results: Between September 14th 2022 and December 21th 2023 a total of 371 arthritis patients (192 rheumatoid arthritis, 100 psoriatic arthritis, 79 spondyloarthritis) on immunosuppressive therapy (Table 1) received a 2nd and a 3rd booster dose. In total, 239/371 (64%) of patients responded to questionnaires asking for adverse events within two weeks following the 2nd booster, and 141/371 (38%) following the 3rd booster dose. A total of 47/239 (20%) vs 17/141 (12 %) reported any adverse event after a 2nd booster dose (bivalent), compared to the 3rd booster (monovalent) (p=0.07). The most frequent adverse events following the 3rd booster were pain at injection site (5%, n=7), fever (4%, n=6) and flu-like symptoms (4%, n=6). However, these adverse events were less frequent compared to after the 2nd booster (pain at injection site (13 %, n=30, p=0.02), fever (5 %, n=11, p=1.00) and flu-like symptoms (10 %, n=23, p=0.07)). In total (4 %, n=6) of patients reported a disease flare after receiving the 3rd, monovalent booster, compared to (6 %, n=14) after the 2nd, bivalent booster (p=0.63). No new safety signals emerged. Conclusion: There were less adverse events overall following the monovalent, 3rd booster, compared to the bivalent, 2nd booster, although not significant, indicating that the XBB.1.5 vaccine is safe in patients with inflammatory joint diseases. REFERENCES: [1] Syversen S.W. et al Arthritis Rheumatol 2022. [2] Bjørlykke K.H. et al Lancet Rheumatol 2022. Acknowledgements: We thank the patients who have participated in the Norwegian study of vaccine responses to COVID-19, and the patient representatives in the study group, Kristin Isabella Kirkengen Espe and Roger Thoresen. We thank all study personnel, laboratory personnel, and other staff at the clinical departments involved. Disclosure of Interests: Hilde S. Ørbo: None declared, Ingrid Jyssum: None declared, Anne Therese Tveter: None declared, Ingrid E. Christensen: None declared, Joe Sexton: None declared, Kristin Hammersbøen Bjørlykke Janssen-Cilag, Tore K. Kvien Grünenthal, Janssen, Sandoz, AbbVie, Gilead, Janssen, Novartis, Pfizer, Sandoz, UCB, AbbVie, BMS, Galapagos, Novartis, Pfizer, UCB, Espen A. Haavardsholm Pfizer, UCB, Novartis, Abbvie, Pfizer, Eli Lilly, Kristin Kaasen Jørgensen Bristol-Myers Squibb, Roche, Sella Aarrestad Provan: None declared, Silje Watterdal Syversen: None declared, Guro Løvik Goll AbbVie/Abbott, Galapagos, Pfizer, UCB.