Evaluation of antibody response to 13-valent pneumococcal conjugate vaccine in psoriasis patients receiving interleukin 17 inhibitors

Introduction: Psoriasis is a chronic, immune-mediated, and widespread skin disease. The role of the IL-23/Th17 pathway in its pathogenesis has been demonstrated and IL-17 inhibitors developed accordingly have become widely used in treatment. However, biologic therapies may increase the risk of infections due to their immunosuppressive effects. In this patient group, which is at risk for vaccine-preventable infections such as pneumococcal disease, evaluating the antibody response to vaccines is of great importance. There is no study in the literature examining the immune response to pneumococcal conjugate vaccine in psoriasis patients receiving IL-17 inhibitors. Therefore, our study aimed to evaluate the antibody response to 13-valent pneumococcal conjugate vaccine in psoriasis patients receiving IL-17 inhibitors. Materials and Methods: This study included 35 psoriasis patients receiving IL-17 inhibitors (secukinumab or ixekizumab) and 11 adults without immunosuppressive conditions as a control group, who applied to Bezmialem Vakıf University Faculty of Medicine Hospital between September 2024 and April 2025. Anti-pneumococcal IgG antibody levels were measured by ELISA in serum samples collected before and 4-6 weeks after the administration of the 13-valent pneumococcal conjugate vaccine. Results: In the psoriasis group, a significant increase in antibody levels was observed after vaccination (OD450: 0.153 → 0.228; p = 0.001). Based on the cut-off value, the antibody positivity rate increased from 28.6% to 60% in the psoriasis group (p = 0.027). The relative increase rate in antibody levels was 78.8% in the psoriasis group and 66.9% in the control group, and this difference was not statistically significant (p = 0.766). Univariate analysis revealed no significant association between antibody positivity and sex, age, comorbidities, or duration of IL-17 inhibitor treatment. However, antibody positivity rate was found to be significantly higher in patients receiving ixekizumab compared to those receiving secukinumab (OR: 8.00; p = 0.018). In multivariate analysis, this difference remained at the limit of significance (p = 0.084). Additionally, linear regression analysis showed that female sex had a positive effect on the antibody increase rate (p = 0.019). Conclusion: Our study demonstrates that psoriasis patients receiving IL-17 inhibitors develop a significant antibody response to the 13-valent pneumococcal conjugate vaccine. Female sex and the use of ixekizumab were observed to be associated with a stronger antibody response. Keywords: Psoriasis, IL-17 inhibitors, secukinumab, ixekizumab, anti-pneumococcal IgG, pneumococcal conjugate vaccine