Immunogenicity and Safety of the Adjuvanted Recombinant Zoster Vaccine in Chronically Immunosuppressed Adults Following Renal Transplant: A Phase 3, Randomized Clinical Trial

1(See the Editorial Commentary by Miller on pages 191–2.)

2Herpes zoster (HZ) results from reactivation of latent varicella zoster virus (VZV), and usually presents as a painful dermatomal rash. The most common complication of HZ is postherpetic neuralgia, chronic pain that can persist for months or even years after resolution of the zoster rash.

3Diminished cellular immunity to VZV increases the risk of HZ. Compared to healthy individuals, persons with impaired cellular immunity, especially those receiving immunosuppressive therapies after organ transplantation, are at increased risk of developing HZ. In particular, solid organ transplant (SOT) patients have a mixed, but mainly cellular immune deficit, induced by chronic immunosuppressive therapy required to prevent organ rejection.

4The observed HZ incidence rates in SOT recipients are up to 9 times higher compared with those in the general population (22–28 vs 3–5/1000 person-years, respectively). However, HZ incidence varies depending on the type of transplanted organ.

5Although efficacy of vaccines in SOT recipients is often suboptimal, immunization against common infectious diseases is currently recommended for SOT candidates and recipients to reduce the risk of infections. While infection may stimulate the immune system, leading to an increased risk of rejection, there is very limited evidence of a correlation between vaccination and allograft rejection. Nevertheless, this remains a general concern for transplant physicians.

6Currently, 2 vaccines are licensed for the prevention of HZ in different regions worldwide. The live attenuated zoster vaccine (Zostavax) is, however, contraindicated in immunosuppressed individuals, including SOT recipients.

7The adjuvanted recombinant zoster vaccine (RZV; Shingrix) is a nonlive vaccine that consists of a truncated form of VZV glycoprotein E (gE) and the GSK AS01B Adjuvant System. RZV is licensed for the prevention of HZ and postherpetic neuralgia in adults ≥50 years of age; it is highly immunogenic and demonstrated >90% efficacy against HZ in all age groups among adults aged ≥50 years, 68% efficacy in autologous hematopoietic stem cell transplant (HSCT) recipients ≥18 years of age, and 87% efficacy in a post hoc analysis in patients ≥18 years of age with hematologic malignancies. The safety profile of RZV was clinically acceptable in these populations.

8In this study, we evaluated the immunogenicity and safety of RZV in renal transplant (RT) patients ≥18 years of age receiving daily immunosuppressive therapy. As the transplant community has a long-established renal allograft monitoring program and because the immunosuppressive therapies used for RTs are also used for other SOTs, RT was selected as a model for SOTs.

9This was a phase 3, randomized, observer-blind, placebo-controlled, multicenter trial, conducted in 9 countries (Belgium, Canada, Czech Republic, Finland, Italy, Panama, Republic of Korea, Spain, and Taiwan) between March 2014 and April 2017. RT recipients were randomized 1:1 to receive 2 doses of RZV or placebo 1–2 months (M) apart, at visits defined as M0 and M1 visits. The randomization algorithm included the following minimization factors: age (18–29, 30–49, or ≥50 years), gender, participant’s highest panel reactive antibody (PRA) or calculated PRA (cPRA) score at/prior to transplant, and maintenance immunosuppressive therapy (use of mycophenolate compounds, calcineurin inhibitors or sirolimus, or corticosteroids). RT patients ≥18 years of age were eligible for participation at 4–18M posttransplantation if they had received an ABO-compatible allograft, had stable renal function, and were free of any allograft rejection in the 3M preceding the first vaccination.

10RT recipients were excluded from participation if they had a primary kidney disease (PKD) known to have a high incidence of recurrence, a previous allograft loss due to recurrent PKD, multiple organs transplanted, or a condition that could interfere with study-required evaluations. Persons were also excluded if they had any systemic autoimmune or potential immune-mediated disease (pIMD) listed in Supplementary Table 1 (exceptions are listed in the Supplementary Text 1B), had clinical history of HZ or varicella, or received HZ/varicella vaccination within the 12M preceding the first dose of study vaccine/placebo. The full list of inclusion and exclusion criteria is provided in Supplementary Text 1.

11All participants provided written informed consent at enrollment. The study protocol was reviewed and approved by independent ethics committees or institutional review boards. The study was conducted in accordance with the Declaration of Helsinki and the principles of Good Clinical Practice. The study is registered at ClinicalTrials.gov (NCT02058589). Anonymized individual participant data and study documents can be requested for further research at www.clinicalstudydatarequest.com.

12Study participants received 2 intramuscular doses of RZV or placebo 1–2M apart in a deltoid muscle. Each 0.5-mL dose of RZV contained 50 μg of recombinant VZV gE antigen and the GSK proprietary AS01B Adjuvant System (containing 50 μg of 3-O-desacyl-4’-monophosphoryl lipid A, 50 μg of Quillaja saponaria Molina, fraction 21 [QS21, licensed by GSK from Antigenics LLC, a wholly owned subsidiary of Agenus Inc, a Delaware, USA corporation], and liposome). Each 0.5-mL dose of placebo contained 20 mg lyophilized sucrose reconstituted with 150 mM sodium chloride solution.

13Humoral immunogenicity was assessed from blood samples collected from each participant at prevaccination (M0 visit), 1–2M post–dose 1 (M1 visit), 1M post–dose 2 (M2 visit), 6M post–dose 2 (M7 visit), and 12M post–dose 2 (M13). Anti-gE antibody concentrations were measured by anti-gE enzyme-linked immunosorbent assay with a technical cutoff of assay quantification of 97 mIU/mL. Cell-mediated immunogenicity (CMI) was evaluated in a subset of participants at the M0, M2, and M13 visits. The frequencies of gE-specific CD4[2+] T cells (CD4 + T-cells expressing at least 2 activation markers of the 4 markers assessed: interferon-γ, interleukin 2, tumor necrosis factor–α, and CD40 ligand) were measured, after in vitro stimulation with a pool of peptides covering the gE ectodomain, by intracellular cytokine staining and detection by flow cytometry as described previously. The cutoff for the CMI vaccine response analysis was 320 positive cells per 106 CD4 + T cells counted.

14Diary cards were provided to all participants to record solicited local (pain, redness, and swelling at the injection site) and general (fever [body temperature ≥37.5°C/99.5°F], headache, fatigue, gastrointestinal symptoms [nausea, vomiting, diarrhea, and/or abdominal pain], myalgia, and shivering) adverse events (AEs) during 7 days (D) after each vaccination, and unsolicited AEs during 30D after each vaccination. Solicited general AEs, as well as unsolicited AEs, were also recorded during 7D before first vaccination to evaluate the baseline values resulting from the underlying condition of participants. AEs were graded from 0 (none/normal) to 3 (severe). Grade 3 AEs were defined as preventing normal activity (for all unsolicited AEs, and for headache, fatigue, gastrointestinal symptoms, myalgia, and shivering), as significant pain at rest, and preventing normal everyday activities (for pain) and having a surface diameter >100 mm (for injection-site redness and swelling).

15All solicited local AEs were considered causally related to vaccination. The causal relationship to vaccination of all other AEs occurring postvaccination was assessed by the investigator. Allograft function (by routine serum creatinine measurements) was reported from first vaccination to study end.

16Serious AEs (SAEs), including biopsy-proven allograft rejections, and pIMDs were recorded from first vaccination to M13. In addition, SAEs related to study participation were recorded from enrollment to study end. If a clinical event was suspicious for HZ per the investigator’s judgement, it was considered a suspected case of HZ. Suspected cases and HZ complications were recorded from first vaccination to study end and constituted AEs/SAEs, as appropriate.

17Study objectives and their evaluation criteria are presented in Table 1.

18Safety and reactogenicity were assessed in the total vaccinated cohort (TVC), which included all participants with at least 1 administered/documented vaccine dose. The analysis of humoral immunogenicity during the vaccination (up to M2) and persistence (up to M13) phases were performed on the applicable according-to-protocol cohorts, which included all participants who complied with the protocol-specified procedures and for whom data were available. The analysis of gE-specific CMI during the vaccination and persistence phases was performed on the applicable according-to-protocol cohorts of the CMI subcohort, which included the first enrolled participants from designated sites that had access to a GSK-validated peripheral blood mononuclear cell processing facility. Further details on statistical methods, including sample size calculation, are provided in Supplementary Text 2.

19A total of 264 RT patients (RZV: 132, placebo: 132) were included in the TVC. Of these, 260 (RZV: 130, placebo: 130) participated through to the last study visit at M13 (Figure 1). Demographic characteristics were balanced between study groups (Table 2). At dose 1, the mean ages were 52.3 and 52.4 years in the RZV and placebo groups, respectively. Most participants were male (RZV: 71.2%, placebo: 68.9%) and white (RZV: 66.7%, placebo: 73.5%).

20Both confirmatory objectives on humoral immunogenicity were met: The humoral vaccine response rate (VRR) in the RZV group was 80.2% (95% confidence interval [CI], 71.9%–86.9%) at M2 (success criterion: lower limit [LL] of 95% CI ≥60%), and the adjusted anti-gE antibody geometric mean concentration (GMC) ratio (RZV over placebo) was 14.00 (95% CI, 10.90–17.99; P <.0001) at M2 (success criterion: LL of 95% CI >3) (Figure 2).

21Among RZV recipients, anti-gE antibody GMCs increased from 1354.4 mIU/mL (95% CI, 1118.3–1640.4 mIU/mL) at prevaccination to 19 163.8 mIU/mL (95% CI, 15 041.5–24 416.0 mIU/mL) at M2 and persisted through M13 at 8545.1 mIU/mL (95% CI, 6753.7–10 811.5 mIU/mL). Postvaccination anti-gE antibody GMCs and humoral VRRs in the placebo group remained near the prevaccination level. Across time points, no apparent differences in anti-gE antibody GMCs were seen linked to the types of maintenance immunosuppressive therapy (Supplementary Table 2). At each time point, humoral immune responses appeared higher in the 18–49 years of age cohort than in the ≥50 years of age cohort (Figure 2). Within the 18–49 years of age cohort, post hoc analyses revealed humoral immune responses similar for ages 18–29 and 30–49 years (Supplementary Table 3).

22Though CMI was measured in a limited subset of participants, both confirmatory CMI objectives were met: The VRR for CMI responses was 71.4% (95% CI, 51.3%–86.8%) in the RZV group at M2 (success criterion: LL of 95% CI ≥50%) (Figure 3); the geometric mean ratio (RZV over placebo) of gE-specific CD4[2+] T-cell frequencies was 17.26 (95% CI, 5.92–50.36; P <.0001) at M2 (success criterion: LL of 95% CI >1).

23At prevaccination, median CD4[2+] T-cell frequencies were 21.2 and 59.7 in the RZV and placebo groups, respectively. In the RZV group, median frequencies increased to 2149.0 at M2 and remained significantly elevated over prevaccination baseline at M13. Postvaccination CD4[2+] T-cell frequencies and CMI VRRs in the placebo group remained near the prevaccination level. At each time point, CMI responses appeared to be higher in the 18–49 years of age cohort (Figure 3). Within the 18–49 years of age cohort, post hoc analyses revealed CMI responses similar for the age 18–29 and 30–49 years of age groups (Supplementary Table 4).

24During the 7D postvaccination period, injection site pain was the most frequent solicited local symptom, reported by 114 (87.0%) of RZV and 11 (8.3%) of placebo participants (Figure 4). Solicited local symptoms in RZV recipients had a median duration of 4D or less.

25During the 7D postvaccination period, myalgia and fever were reported at higher rates by RZV compared to placebo participants. Myalgia was reported by 65 (49.6%) RZV participants and by 31 (23.5%) placebo participants; and fever by 21 (16.0%) RZV participants and 5 (3.8%) placebo participants (Figure 4). Myalgia, shivering, and fever appeared to be more frequently reported post- than prevaccination in the RZV group (Supplementary Figure 1B and 1C).

26During the 7D prevaccination period, at least 1 unsolicited symptom was reported by 9 (6.8%) RZV participants and 7 (5.3%) placebo participants. No grade 3 unsolicited AEs were reported in either study group during this time period.

27During the longer, 30D postvaccination period, at least 1 unsolicited symptom (any grade) was reported by 51 (38.6%) RZV participants and 44 (33.3%) placebo participants. Grade 3 unsolicited symptoms were reported by 7 (5.3%) RZV and 5 (3.8%) placebo participants (Table 3).

28From first vaccination through M13, SAEs were reported by 26 (19.7%) RZV and 33 (25.0%) placebo participants. Of these, 3 SAEs (febrile neutropenia, mucosal inflammation, and Burkitt lymphoma) were considered as causally related to vaccination and were reported by 1 placebo recipient. Overall, the most frequent SAEs classified by Medical Dictionary for Regulatory Activities System Organ Class were “infections and infestations.”

29Throughout the entire study, 1 fatality (0.8%) was reported in each of the study groups (RZV: purulent meningitis; placebo: coronary artery disease complicated by vein graft thrombosis and myocardial infarction; Table 3). Neither was considered causally related to vaccination by the investigator.

30No biopsy-proven renal allograft rejections occurred from first vaccination up to 30D after the last dose in either group. Throughout the entire study, 4 (3.0%) and 7 (5.3%) biopsy-proven rejections occurred in the RZV and placebo groups, respectively (Table 3). Of these, 1 in the RZV group and all 7 in the placebo group occurred in participants with low rejection risk based on PRA/cPRA predictions (PRA/cPRA, 0–19%).

31Serum creatinine level increases >1.5-fold were detected in 4 (3.1%) of RZV and 4 (3.0%) of placebo recipients. Percentages of participants with >1.75-fold or >2-fold increases were also similar in the 2 study groups (Table 3).

32No pIMDs were reported from first vaccination up to 30D after the last dose in either group. Through M13, pIMDs were reported by 4 (3.0%) RZV and 2 (1.5%) placebo participants (Table 3).

33In the TVC, 3 (2.3%) RZV recipients and 7 (5.3%) placebo participants reported suspected HZ episodes. One of the episodes occurred in a participant who had not yet received both RZV doses.

34Our study demonstrates that RZV was immunogenic in RT patients aged ≥18 years under chronic daily immunosuppression. Humoral and cellular immune responses to vaccination persisted through 1 year after vaccination. No safety concerns were identified in this study. A results summary contextualizing the results and potential clinical relevance is provided in Figure 5 to assist communications to the patient.

35RZV induced robust humoral and cell-mediated immune responses to gE when administered 4–18M after RT. Vaccination took place when RT maintenance immunosuppression levels were achieved, and prior to the rise of HZ incidence in this population. As seen in other RZV trials in immunocompromised populations such as autologous HSCT recipients, patients with solid tumors, and patients with hematologic malignancies, RZV was found to be immunogenic as shown by high VRR for both humoral and cellular immune responses, as well as by anti-gE antibody GMC ratios and CD4[2+] T-cell frequency ratios.

36Anti-gE antibody GMCs and humoral VRRs at 1M and 12M post–dose 2 were in similar ranges with those in autologous HSCT recipients ≥18 years of age. In this study, both RZV-induced humoral and cellular immune responses appeared to be higher in the younger (18–49 years of age) compared to the older (≥50 years of age) age groups across all time points. In the older age group of this study, humoral GMCs and VRRs, as well as CMI VRRs, at 1M and 12M post–dose 2 were lower than in immunocompetent adults of the same age. However, gE-specific CD4[2+] T-cell frequencies at 1M and 12M post–dose 2 in the older age group were in similar ranges with those in immunocompetent adults ≥50 years of age. As VZV-specific cellular immunity is believed to be the main mechanistic driver of protection against HZ, RZV vaccination is expected to reduce the risk of HZ in RT recipients. The responses of adults ≥50 years of age in our study are likely a result of the combined effects of immunosenescence and the use of maintenance immunosuppressive therapy.

37Though the number of participants in each subgroup was low, our results indicate that RZV-induced humoral immune responses were similar in range across the different immunosuppressive regimens assessed.

38In line with the reactogenicity profile of RZV in the pivotal phase 3 efficacy trials, RZV recipients reported solicited local symptoms more frequently than placebo recipients. Compared to placebo, the frequency of solicited general symptom reporting by RZV recipients increased only for myalgia after dose 1 and for myalgia, shivering, and fever after dose 2. Solicited AEs were primarily mild to moderate and transient in nature. In the RZV group, only 1 participant (<1%) withdrew from the study before receiving dose 2, due to an AE (fever) that persisted for 2 days after receiving RZV dose 1.

39Overall, no apparent differences were observed between study groups in the occurrence of unsolicited AEs, SAEs (including fatalities), pIMDs, biopsy-proven allograft rejections, or allograft function changes. Overall, the reported events are consistent with the background disease or concomitant medications. Indeed, RZV does not impact allograft function, as observed through creatinine measurements or rejection rate. A lower rate of suspected HZ cases was reported in RZV vs placebo recipients (3 vs 7 suspected cases).

40Taken together with the clinically acceptable safety profile, the benefit-risk profile of RZV in RT recipients appears favorable, though vaccine effectiveness in this population has not been established.

41Our results should be interpreted considering the study’s strengths and limitations. Study strengths include the fact that randomization was performed using several minimization factors leading to comparable baseline characteristics between the 2 study groups. Considering the high rate of solicited general AEs in the RT population, these were also recorded for 7D before vaccination, to indicate the increase of such AEs due to vaccination. Renal allograft function and rejections were followed up for 1 year. As the study was carried out in a limited number of geographic regions, the racial heterogeneity was not very broad. However, in an earlier study, race did not appear to impact RZV immunogenicity. Furthermore, the analysis by age and by immunosuppressive treatment regimen should be interpreted with caution as the number of participants in each of these subgroups was low. While this study was not designed to establish the immunologic correlates of protection or determine the vaccine efficacy in this population, the study’s safety profile and robust immune responses suggest a favorable benefit-risk assessment for RZV in RT recipients.

42In conclusion, RZV was immunogenic in RT recipients receiving daily immunosuppressive therapy. Humoral and cellular immunogenicity persisted through the 1-year evaluation, while no vaccine-related concerns were identified. No apparent differences were observed between RZV and placebo recipients for allograft function and rejections.

43Supplementary materials are available at Clinical Infectious Diseases online. Consisting of data provided by the authors to benefit the reader, the posted materials are not copyedited and are the sole responsibility of the authors, so questions or comments should be addressed to the corresponding author.