Immunogenicity of Quadrivalent Influenza Vaccine for Patients with Inflammatory Bowel Disease Undergoing Immunosuppressive Therapy.

Background and Aims: No reports have described the immunogenicity and boosting effect of the quadrivalent inactivated influenza vaccine (QIV) in adults with inflammatory bowel disease. Methods: Adults with Crohn's disease or ulcerative colitis were randomly assigned to a single vaccination group or booster group, and a QIV was administered subcutaneously. Serum samples were collected before vaccination, 4 weeks after vaccination, and after the influenza season in the single vaccination group. In the booster group, serum samples were taken before vaccination, 4 weeks after the first vaccination, 4 weeks after the second vaccination, and after the influenza season. We measured hemagglutination inhibition antibody (HAI) titer and calculated the geometric mean titer ratio (GMTR), seroprotection rate, and seroconversion rate. Results: In total, 132 patients were enrolled. Twenty-two patients received immunomodulatory monotherapy and 16 received anti-tumor necrosis factor-α (anti-TNF-α) single-agent therapy. Fifteen patients received combination therapy comprising an immunosuppressant and anti-TNF-α agent. Each vaccine strain showed immunogenicity satisfying the European Medicines Agency criteria with a single inoculation. The booster influenza vaccination did not induce additional response. In patients administered infliximab, the seroprotection rate and seroconversion rate tended to be lower in patients who maintained blood concentrations [seroprotection rate: H1N1: OR, 0.37 (95% CI, 0.11-1.21); H3N2: 0.22 (0.07-0.68); seroconversion rate: H1N1: 0.23 (0.06-0.91); H3N2: 0.19 (0.06-0.56)]. Conclusion: Single dose QIV showed sufficient immunogenicity in patients with inflammatory bowel disease, and a boost in immunization by additional vaccination was not obtained. Additionally, immunogenicity was low in patients receiving infliximab therapy.