Immunogenicity, Efficacy and Safety of Recombinant Herpes Zoster Vaccine in Frail Patients

Herpes zoster (HZ) is a serious health problem whose incidence and severity increase with the decline of cell-mediated immunity (CMI) because of age and immunocompromised (IC) status. Subclinical reactivation are described and may boost the adaptive specific immunity. T cells play a major role in preventing reactivation of Varicella Zoster virus (VZV), with a contribution of both CD4 and CD8 T cells. Accordingly, the suppression of VZV-specific T cells preceded the occurrence of HZ. Moreover, several observations support a role of B cells in contributing to the overall protection against HZ as patients with primary antibody deficiency, common variable immunodeficiency, or patients treated with B-cell depleting therapies or Janus Kinase inhibitors (JAKis) show a higher risk of HZ. The functional effectiveness of CMI can be significantly affected by different diseases (e.g. cancer and immune-mediated inflammatory diseases, IMIDs) and/or by ongoing immune-targeted therapy, giving these patients at high risk for VZV reactivation. The new recombinant zoster vaccine (RZV) reduces the risk of HZ, and vaccination is encouraged in IC individuals, including those with cancer and IMIDs. Despite the efficacy and safety of RZV in healthy adults, data on IC patients are scarce. In particular, the immunogenicity of the new vaccine in frail subjects is not fully understood. On the one hand, immunosuppressive treatments can compromise the residual immunity to VZV but also the response to RZ . Several therapies are known to affect B cell response such as Rituximab or CAR T cells; other treatments reduce the T cell functionality, such as T-cell inhibitors (Cytotoxic T-lymphocyte Antigen 4-Immunoglobulin, CTLA4-Ig; abatacept), the JAK is, as well as by chemotherapy. To date, the vaccination is not approved in paediatric patients. However, the investigation of the VZV-specific immunological profile in frail paediatric patients could represent a valuable tool for understanding the potent