Abstract
Immune-modifying treatment in inflammatory bowel disease (IBD) impairs the humoral response. The role of T lymphocytes in this setting is still unclear. This study aims to assess if a booster shot (third dose) of BNT162b2 mRNA COVID-19 vaccine enhanced the humoral response and elicited cellular immunity in IBD patients on different immuno-therapy regimens compared to healthy controls (HCs). Five months after a booster dose, serological and T-cell responses were assessed. The measurements were described using geometric means with 95% confidence intervals. The differences between study groups were assessed by Mann-Whitney tests. Seventy-seven subjects (n = 53 IBD patients and n = 24 HCs), who were fully vaccinated and not previously SARS-CoV-2 infected, were recruited. Regarding the IBD patients, 19 were affected by Crohn's disease and 34 by ulcerative colitis. During the vaccination cycle, half of the patients (53%) were on stable treatment with aminosalicylates, and 32% were on biological therapy. No differences in antibody concentrations between IBD patients and HCs, nor T-cell responses, were found. Stratifying IBD patients based on the type of treatment (anti-TNFα agents vs. other treatment regimens), a decrease only in antibody titer (p = 0.008), but not in cellular response, was observed. Even after the COVID-19 vaccine booster dose, the TNFα inhibitors selectively decreased the humoral immune response compared to patients on other treatment regimens. The T-cell response was preserved in all study groups. These findings highlight the importance of evaluating T-cell immune responses following COVID-19 vaccination in a routine diagnostic setting, particularly for immunocompromised cohorts.