Clinical Trials

Inclusion Criteria:

To be eligible for study participation, an individual must meet all of the following criteria:

1. Ability to understand, and willingness and ability to read and sign, the informed consent form.
2. Ability to understand and follow instructions and study procedures.
3. Willingness to comply with all study procedures and be available for the duration of the study.
4. Ability to take oral medication, and are willing to adhere to study medication regimen.
5. Age 18 years or older.
6. Diagnosed with HZO in one eye based on both of these criteria:
   1. History of characteristic unilateral vesicular rash in the dermatomal distribution of cranial nerve V1.
   2. Medical record documentation of an episode of active dendriform epithelial keratitis, stromal keratitis, endothelial keratitis, and/or iritis due to HZO within the preceding year. This episode of active anterior segment ocular disease may be due to HZO of recent onset (within the preceding 6 months); or chronic HZO (with onset six or more months ago); may be new, worsening, or recurrent disease after a period of inactivity; and may occur after medication was reduced.

   i. Study participants with chronic HZO must be on a stable treatment regimen and off antivirals for at least 30 days before enrollment. Study participants with chronic HZO who do not meet this criterion may be rescreened, if they are able to meet this criterion within 3 months after the study visit. (This is not a requirement for study participants with recent onset HZO, who may be enrolled at any time, preferably after completing recommended acute antiviral treatment, if prescribed, is completed).

7. For females with reproductive potential, willingness to use highly effective contraception (e.g., hormonal contraception, barrier contraception, intrauterine device, or abstinence).

Exclusion Criteria:

An individual who meets any of the following criteria will be excluded from participation in this study:

1. History of immunocompromised status as defined by current CDC contraindications for the vaccine against zoster (44).
   1. Study participants who are diagnosed with leukemia, lymphomas or other malignant neoplasms affecting bone marrow or lymphatic system, unless leukemia in remission and off chemotherapy for at least 3 months.
   2. Study participants who are diagnosed with Acquired Immune Deficiency Syndrome (AIDS) or presents with other clinical manifestations of Human Immunodeficiency virus (HIV) including CD4 count of ≤ 200 cells/ml.
   3. Study participants on immunosuppressive therapy including:
   i. High-dose corticosteroids (greater than equivalent of prednisone 20 mg/day within 1 month) ii. Chemotherapy, other than low dose used for treatment of immune-mediated diseases within 3 months iii. Study participants receiving recombinant human immune mediators and immune modulators, especially antitumor necrosis agents, within 1 month prior to enrollment d. Study participants with unspecified cellular immunodeficiency. e. Study participants with history of hematopoietic stem cell transplantation.
2. Medical history of a systemic disease and thought likely to meet one of the exclusion criteria listed in exclusion criterion #1 during the 18-month study period.
3. Renal insufficiency:
   1. Requires dialysis or has history of renal transplant or
   2. eGFR less than 45, determined within 30 days preceding enrollment.
4. Allergy or adverse reaction to valacyclovir or acyclovir.
5. History of vaccination against zoster within one month prior to enrollment. Study participants who meet this exclusion criterion may be rescreened.
6. Keratoplasty or keratorefractive surgery of the involved eye with zoster.
7. On systemic antivirals with activity against herpes within the past 30 days, including acyclovir, valacyclovir, or famciclovir, for any reason except for treatment of acute HZO, including investigational drug trial.
8. History of another condition that may require treatment with one of these three antivirals listed above in exclusion criterion #7, during the course of the study; study participants who require chronic suppressive antiviral treatment with these medications will be excluded.
9. Sexually active women who are pregnant, nursing, or in their reproductive years who do not agree to use contraception during the 1-year treatment period.
10. Incarceration
11. Any condition or circumstance that in the opinion of the study investigator, would place the study participant in increased risk or affect his/her full compliance or completion of the study.
12. Participation in a clinical study testing a drug, biologic, device or other intervention within the last 30 days from enrollment visit. Study participants who meet this criterion may be rescreened.