The goal of this clinical trial is to compare responses to Varicella Zoster vaccination between transplant patients on different medication regimens, and their healthy co-habitants. The main questions it aims to answer are:

1. Are there differences in vaccination immunological responses in transplant patients on different immunosuppression regimens?
2. Are there differences in vaccination immunological responses between transplant patients and their healthy co-habitants? Participants will all receive a 2-dose course of SHINGRIX recombinant Zoster vaccination, and have immunological responses measured and compared at 5 timepoints between 1 week to 1 year post-vaccination.

1. Population - Group 1. Healthy co-habitants (n = 30)

   Inclusion criteria:

   • Household co-habitant of transplant recipient in trial
   • Aged >50 years
   • Previous documented infection with VZV (known infection history or positive VZV IgG result)

   Exclusion criteria:

   • Aged <50 years
   • Unable or unwilling to provide informed consent to participate in the trial
   • Known allergy to or intolerance of the contents of the RZV vaccine
   • No previous infection with VZV (chickenpox)
   • History of primary immunodeficiency, documented vaccine hypo-responsiveness, or active immunosuppressive therapy

2. Population - Groups 2-4. Transplant recipients (n = 90)

   Inclusion criteria:

   • Organ transplant recipients

     -- Specific immunosuppression regimen

     • Tacrolimus, mycophenolate, prednisolone (n = 30, Group 2)
     • Tacrolimus, mTORi, prednisolone (n = 30, Group 3)
     • mTORi, mycophenolate, prednisolone (n = 30, Group 4)

   • Aged >18 years

   • estimated GFR > 15 mL/min/1.73m2

   • Previous documented infection with VZV (known infection history or positive VZV IgG result)

   Exclusion criteria:

   • Aged <18 years
   • Unable or unwilling to provide informed consent to participate in the trial
   • No previous infection with VZV (chickenpox)
   • Known allergy to or intolerance of the contents of the RZV vaccine
   • Current pregnancy

3. Population - Group 5. Other (n = 10)

   Inclusion criteria:

   • Immunosuppressed patient receiving single-agent rapamycin immunosuppression
   • Aged >18 years
   • Previous documented infection with VZV (known infection history or positive VZV IgG result)

   Exclusion criteria:

   • Aged <18 years
   • Unable or unwilling to provide informed consent to participate in the trial
   • Known allergy to or intolerance of the contents of the RZV vaccine
   • No previous infection with VZV (chickenpox)
   • Known allergy to or intolerance of the contents of the RZV vaccine
   • Current pregnancy
   • History of primary immunodeficiency, documented vaccine hypo-responsiveness, or active immunosuppressive therapy

4. Population - Group 6. Dialysis group (n = 30)

Inclusion criteria:

• Kidney failure receiving haemodialysis as kidney replacement therapy
• Aged >18 years
• Previous documented infection with VZV (known infection history or positive VZV IgG result)

Exclusion criteria:

• Aged <18 years
• Unable or unwilling to provide informed consent to participate in the trial
• Known allergy to or intolerance of the contents of the RZV vaccine
• No previous infection with VZV (chickenpox)
• Known allergy to or intolerance of the contents of the RZV vaccine
• Current pregnancy
• History of primary immunodeficiency or active immunosuppressive therapy

Identifiable data will not be publicly released, however, de-identified data will be made available in combination with publication of study results either as supplementary material or on public repository. Study protocol and statistical analysis plan will be made available as supplementary material with publication of results.

Data will be made available following publication of trial results, and will be available in perpetuity.

Trial results and supporting information outlined above will be made available through open access publishing.