P054 Effectiveness and waning of SARS-CoV-2 booster vaccination against COVID-19 hospitalisation and death in adults with immune-mediated inflammatory diseases: a nested case-control analysis of linked primary care, hospitalisation and mortality data from England

Background/Aims There is limited evidence on the effectiveness of SARS-CoV-2 vaccine boosters in patients with immune mediated inflammatory diseases (IMIDs) and the durability of protection offered. We undertook a nested case-control study to assess the association between hospitalisation or death due to COVID-19 and booster vaccinations among UK adults with IMIDs. Methods Using data from the Clinical Practice Research Datalink Aurum linked to hospitalisation and mortality records, we ascertained adults (≥18 years) diagnosed with IMIDs prescribed steroid sparing immune-suppressing drug, and with ≥1 vaccination against COVID19 before study start. Cases were hospitalised for or dying due to COVID-19 between September 2021 and March 2023 and were matched with up to ten controls on age, sex, and follow-up duration. Adjusted odds ratios (aORs) were estimated using multivariate unconditional logistic regression for the association between COVID-19 hospitalisation or death and the number of boosters, individual booster vaccinations, and time since latest booster. Analyses were adjusted for demographic factors, comorbidities, deprivation, healthcare utilisation, corticosteroid use, and prior COVID-19. Prespecified subgroup analyses assessed effects stratified by: age (>65 years), sex, IMID category, and immunosuppressant class. Results We included 2,178 cases and 17,750 controls (mean age 65.5 years; 60.2% women, 39.8% men). Hospitalisation or death due to COVID-19 was negatively associated with three (aOR: 0.42, 95% CI 0.33-0.52), two (aOR: 0.48, 95% CI 0.40-0.57), and one booster (aOR: 0.68, 95% CI 0.59-0.78) respectively compared to no boosters. Comparable effects were observed in those older than 65 years. The negative association was present for individual booster doses, with aOR (95% CI): 0.60 (0.51-0.71) for the Autumn 2021, 0.54, (0.44-0.67) for the Spring 2022, and 0.37, (0.29-0.48) for the Autumn 2022 boosters respectively. Vaccine effectiveness waned with time since last booster: aOR 0.54 (0.46-0.64) at 14-90 days, and 0.71 (0.61-0.83) at 91-180 days, with no significant protection beyond six months (0.91; 0.75-1.11). Conclusion SARS-CoV-2 booster vaccination was associated with protection against hospitalisation and death due to COVID-19 in IMIDs prescribed immunosuppressant drugs. These findings support six-monthly booster vaccinations in this high-risk population. Disclosure N.S. Kumar: None. G. Nakafero: None. A. Abhishek: None.