P755 Impaired antibody seroconversion after COVID-19 vaccination and negative impact of immunosuppressive treatment in Inflammatory Bowel Disease. Results from a multicentre, prospective study of GETECCU (VACOVEII)

Abstract Background COVID-19 vaccination has been suggested as very effective in patients with Inflammatory Bowel Disease (IBD), but most studies assess antibody levels within a few weeks after vaccination and do not use the most recent recommendations as seroconversion cut-off. The objective of VACOVEII study is to evaluate the antibody response to vaccination at 6 months using these recommendations, the improvement after a booster dose and the effect of the immunosuppressive therapy (IST). We present the intermediate results of the study. Methods Spanish multicentre, prospective and case-control study. 18 years or older IBD patients fully vaccinated against COVID-19 were included. Those with previous COVID infection were not included, but not excluded for the next analyses if the infection was subsequent. Main outcomes were anti-SARS-CoV-2 spike protein antibody (anti S) concentrations and rate of seroconversion (defined above the protection threshold of 260 BAU/mL), measured 6 months after vaccination at a single centralized laboratory. The effect of IST on the main outcomes was analysed, adjusted by age, vaccine type and COVID infection. Groups of treatment considered for the analysis were: patients without IST (without treatment or under salicylates alone), anti-TNF in combination with immunomodulators (IMM), anti-TNF in monotherapy, IMM in monotherapy, ustekinumab and anti-integrin. Results We included 313 patients with IBD (46.5% ulcerative colitis and 52.3% Crohn’s disease, median age 49 years) vaccinated either with non-mRNA vaccines (14%) or mRNA vaccines (86%). Baseline therapy was: 124 patients without IST, 21 with anti-TNF plus IMM, 67 with anti-TNF in monotherapy, 54 with IMM in monotherapy, 28 with ustekinumab and 19 with anti-integrin. Mean anti S concentrations were significant lower in patients with anti-TNF compared with patients without IST (Figure 1). In multivariable analysis, lower antibody concentrations were independently associated with anti-TNF treatment, non-mRNA vaccines and older age. Within the patients with no COVID infection during the follow-up, we found very low rates of seroconversion in patients with anti-TNF (14.1%), ustekinumab (30.8%) and IMM in monotherapy (34.9%), compared with patients without IST (51.5%) (Table 1). In multivariable analysis, anti-TNF treatment, non-mRNA vaccines and older age were independently associated with lower rates of seroconversion, as well as ustekinumab and IMM in monotherapy (Table 2). Conclusion COVID-19 vaccine-induced antibody seroconversion in patients with IBD, measured at 6 months and according to >260 BAU as protection threshold, is clearly lower than previously reported, with a profound impact by some IST therapies, mainly anti-TNF, besides age and type of vaccine.