Durability of Antibody Responses to SARS-CoV-2 Vaccination over 12 Months in Pediatric Inflammatory Bowel Disease

Background/Objectives: Severe acute respiratory syndrome (SARS-CoV-2) has had a profound global impact and continues to represent a health challenge worldwide. The durability of SARS-CoV-2 vaccine responses in pediatric inflammatory bowel disease (PIBD) patients receiving biologic therapies is unknown. This study aimed to quantify SARS-CoV-2 antibody responses post vaccination in these immunosuppressed patients over 12 months. Methods: Prospective study comparing antibody responses against SARS-CoV-2 spike protein at 1, 3, 6, and 12 months in PIBD patients aged 5–18 years treated with anti-tumor necrosis factor alpha (anti-TNF) therapies with or without an immunomodulator (IM) versus vedolizumab. Results: Between 1 May 2021 and 1 May 2022, 194 participants on anti-TNF monotherapy (n = 78), anti-TNF with IM (n = 83), vedolizumab (n = 15), and steroids (n = 18) were recruited. Anti-SARS-CoV-2 spike levels increased after the first vaccine and were further boosted 1 month after the second dose. Linear mixed-effects modelling showed antibody waning over time (effect difference −2509 IgG AU/mL per week [95%CI: −4998–−20, p = 0.048]), counterbalanced by booster doses (effect difference 184,138 IgG AU/mL per additional vaccine dose [95%CI: 138,342–229,934, p < 0.001]). Receiving anti-TNF therapy contributed to reduced antibody responses compared to vedolizumab (anti-TNF monotherapy effect difference: −212,640 [95%CI: −336,928–−88,351] p = 0.001; anti-TNF with IM: −151,880 [95%CI: −277,309–−26,451] p = 0.018). Seroconversion and breakthrough infection rates were similar between groups, and all infections were mild, without hospitalizations. Conclusions: Although SARS-CoV-2 antibody responses were attenuated in PIBD patients receiving anti-TNF therapy compared with vedolizumab, this did not impact protection, as seroconversion and breakthrough infection rates were similar, with no hospitalizations. These data reinforce the importance of updating vaccines and, in particular, SARS-CoV-2 vaccines in immunosuppressed PIBD patients on advanced therapies.