1. Introduction
Acute gastroenteritis due to norovirus infection represents in a significant global health burden, with high levels of morbidity across all ages, and the possibility of mortality in at-risk groups, such as the very young, very old, and the immunocompromised [
1]. Prophylactic vaccination is a potential strategy for preventing norovirus gastroenteritis, and several candidate vaccines are in clinical development [
2]. The most advanced candidate is HIL-214 (formerly TAK-214), a bivalent virus-like particle (VLP) vaccine containing two VLPs targeting the predominant norovirus genogroups responsible for most human disease, GI.1 and GII.4 [
3]. As antigenic drift has resulted in multiple variants of GII.4, the vaccine GII.4 VLP consists of a consensus sequence (GII.4c) constructed from three different naturally occurring GII.4 genotype variants, 2002 (Houston), 2006a (Yerseke), and 2006b (Den Haag). The construct is intended to induce a broad immunity against diverse variants within the GII.4 genotype [
4,
5].
Several clinical trials have demonstrated immunogenicity and an acceptable safety profile in adults and older-adult volunteers for various compositions of HIL-214, which contain different ratios of the two VLP antigens and are adjuvanted with aluminum hydroxide (Al(OH)
3) with or without monophosphoryl lipid A (MPL) [
6,
7,
8]. From those trials, a single-dose composition, comprising 15 μg GI.1 and 50 μg GII.4c VLPs with 0.5 mg Al(OH)
3, was selected for adults. No added benefit to immunogenicity was observed from a second dose or from the inclusion of MPL in the vaccine composition [
7,
8]. This single-dose composition was subsequently evaluated in a proof-of-concept study involving US Navy recruits, where the vaccine efficacy against moderate-to-severe gastroenteritis associated with any norovirus genotype was estimated to be 61.8% (95.01% CI, 20.8–81.6) [
9].
The current Phase 2 study was designed to assess the long-term immunogenicity of HIL-214 in adult participants pooled from three previous clinical trials, up to five years after vaccination. This Phase 2 study considered fifteen different regimens because two of the three trials were dose-finding in design [
7,
8]. However, in this report, the immunogenicity analysis focuses on the 15/50/0 composition (i.e., dose quantities in µg of GI.1 VLP/GII.4c VLP/MPL) administered as a single dose, because these VLP quantities and this regimen were selected for further clinical development. The analyses of the one-dose 15/50/15 regimen and the two-dose 15/50/0 regimen were conducted to support the analysis of the one-dose 15/50/0 regimen, and as with the one-dose 15/50/0 regimen, both regimens were used in at least two of the previous trials [
6,
7,
8]. The primary analysis relied on an assay for titering serum antibodies that block VLP binding to histoblood-group antigens (HBGA)—sugar moieties on intestinal enterocytes that can bind human norovirus [
10]. Although human norovirus can now be cultured in intestinal organ cultures, the HBGA-blocking assay is considered as a quasi-neutralization assay that remains better suited for high-throughput processing [
11].
2. Methods
2.1. Study Design
This long-term follow-up Phase 2 study, designated as NOR-213, is registered on ClinicalTrials.gov (NCT03039790) and EudraCT (2016-004288-37). The study population consisted of adults who had previously participated in 1 of 3 trials (NOR-107, NOR-204, and NOR-210) conducted at 11 trial sites—2 in Belgium and 9 in the United States—between 21 February 2017 and 22 July 2021. The vaccine candidate in those trials, initially developed and supplied by Takeda Vaccines as TAK-214, is currently being advanced through clinical development by HilleVax as HIL-214. All participants completed and signed a new informed consent for this study. The protocol was approved by the ethics committees of the respective study sites and conducted according to current guidelines of the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use and good clinical practice. The three initial trials were as follows:
NOR-107 (NCT02038907 [
7]) was conducted at 2 sites in Belgium between 28 March 2014 and 19 June 2015 in 420 adults aged 18 to 64 years. Participants received 1 or 2 doses of 11 different compositions of GI.1 and GII.4c with or without 15 µg or 50 µg of MPL and/or 167 µg or 500 µg Al(OH)
3 as adjuvants—see
Table 1. Participants from NOR-107 entered the present study during their third year after vaccination.
NOR-204 (NCT02661490 [
8]) was conducted at 10 sites in the US, mainly involving 294 older adults aged ≥60 years, with a control group of 26 adults aged 18 to 49 years, who received 1 or 2 doses of 15 µg GI.1 and 50 µg GII.4c with 500 µg Al(OH)
3, with or without 15 µg MPL—see
Table 1. Participants from NOR-204 entered the present study during their second year after vaccination.
NOR-210 (NCT02475278 [
6]) was conducted at 1 site in the US in 50 adults aged 18 to 49 years, who received 1 dose of 15 µg GI.1 and 50 µg GII.4c with 500 µg Al(OH)
3. Participants from NOR-210 entered the present study during their second year after vaccination.
For inclusion in the present study, male or female volunteers aged over 18 years must have previously received at least 1 intramuscular dose of HIL-214 in 1 of the previously mentioned trials and must not have received any investigational product from any other clinical trial within 30 days prior to the start of this study. Acceptance into the study was also contingent on the investigator’s assessment that the volunteer would complete the follow up, provide the required blood samples, and had no behavioral or cognitive impairment or psychiatric condition that might interfere with their participation. For inclusion into the initial trials, all participants had been required to be in good health, or in a medically stable health condition.
2.2. Objectives
Primary and secondary objectives were to evaluate the humoral immune response annually for up to five years after at least one dose of HIL-214, as measured by HBGA-blocking and pan-Ig assays, respectively. An assessment of antibody-secreting cell (ASC) frequency was included as an exploratory objective.
2.3. Endpoints
The primary immunogenicity endpoints were the geometric mean titers (GMTs) of GI.1-specific and GII.4c-specific HBGA-blocking antibodies. Secondary endpoints were GMTs of GI.1-specific and GII.4c-specific pan-Ig antibodies. Exploratory endpoints included the frequency of GI.1-specific and GII.4c-specific ASCs. All primary, secondary, and exploratory evaluations were performed at yearly intervals up to 5 years after primary vaccination.
2.4. Procedures
At the initial trial visit, a baseline blood sample was taken from each participant, with further blood draws occurring on Day 28 or 56 (one month after the first or second dose) and at six months (Day 208 or 211 depending on the study). In this extension study, blood samples were drawn at two years and then at one-year intervals until the fifth anniversary of their first HIL-214 dose. At each study visit, participants were interviewed to determine if any serious adverse events (SAEs) had occurred since the previous visit. These SAEs were assessed by the investigator for severity and potential causality related to the vaccine. Participants were instructed to report any SAE immediately or within 24 h to the investigator for further investigation. A data monitoring committee, which was already in place to oversee the risks, benefits, and scientific validity of the entire HIL-214 development program, had oversight of the present study.
2.5. Immunogenicity Assays
Sera were prepared immediately from blood draws at each study visit and shipped at −20 °C to the PPD Bioanalytical Laboratory (Richmond, VA, USA). HBGA-blocking antibodies were measured as described previously [
7,
10]. Pan-Ig antibodies were measured by the enzyme-linked immunosorbent assay. Both assays were performed with 2-fold dilutions of serum samples, where a titer represents the reciprocal of the dilution. ASCs were identified in an ELISpot assay of cultured peripheral-blood mononuclear cells (PBMCs), largely based on a previously published method [
12] and performed as a service by CEVAC—Ghent University (Ghent, Belgium). Briefly, memory B cells were induced to differentiate into plasma cells by culturing PBMCs with R848 (InvivoGen, Toulouse, France) and recombinant human IL-2 (R&D Systems, Abingdon, UK) for 5 days at 37 °C/5%CO
2. Cells were then transferred into (96-plate) culture wells coated with 100 µL of GI.1 or GII.4c VLPs at 10 µg/mL or with 100 µL goat–anti-human IgG at 50 µg/mL (Affinipure, Jackson ImmunoResearch Europe Ltd. Ely, UK) to enumerate GI.1- or GII.4c-specific antibodies or IgG-secreting plasma cells, respectively. The antibody/antigen spots formed were detected by a conventional immunoenzymatic procedure. The results were expressed as frequencies of GI.1- and GII.4c-specific memory B cells per million of IgG-producing memory B cells.
2.6. Statistics
Data from participants who received a given HIL-214 composition were pooled for each time point for the analysis (see
Table 1). For this trial, there were two analysis sets defined: the full analysis set (FAS), which consisted of all participants with data from at least one follow-up time point, and the per-protocol set (PPS), which included all participants in the FAS with no major protocol deviations that could potentially confound the primary (immunogenicity) endpoint. An additional post hoc analysis of the immunogenicity data was performed, excluding data from participants considered to have had a natural norovirus infection from the time point after the infection occurred. Natural infection was indicated by a ≥4-fold increase in titer, over the most recent previously collected titer, for either antibody assay (HBGA-blocking or pan-Ig) or either GI.1 or GII.4c specificity. A third subset, the ASC subset, consisted of participants originally included in the cell-mediated immunity (CMI) subsets from the NOR-107 and NOR-204 trials and was analyzed descriptively for ASC frequencies. Safety data, including the occurrence of serious adverse events or deaths, are presented descriptively. All statistical analyses were generated using SAS Version 9.4 (SAS Institute Inc., Cary, NC, USA).
3. Results
3.1. Disposition and Demographics
In total, 528 individuals were enrolled into this long-term follow-up study comprising participants from NOR-107, NOR-210, or NOR-204 clinical trials (
Figure 1;
Table 1). Fifty-three participants discontinued the study, including twenty-two lost to follow-up, twenty-one who withdrew, six who died, and four who discontinued for unspecified reasons. In both the FAS and the PPS, 105 participants were 1-dose 15/50/0 recipients (Arm 8A), 67 were 2-dose 15/50/0 recipients (Arm 8B), and 52 were 1-dose 15/50/15 recipients (Arm 5A). A subset analyzed for ASCs consisted of 234 participants exclusively from NOR-107 and NOR-204, including 34 recipients from Arm 8A who received a single dose of 15/50/0.
Overall, the mean age was 54 years, with the majority of participants (77%) aged between 18 and 64 years (
Supplementary Table S1). Sixty-one percent of participants were female. In terms of race, most participants identified as White (97%). In terms of ethnicity, most participants (65%) did not report a category, and 32% reported being not Hispanic or Latino. For recipients of the 15/50 GI.1/GII.4c compositions, mean ages differed: in Arm 8A, the mean age was 54 years, compared with 64 and 62 years in Arms 8B and 5A, respectively (
Table 2). Additionally, fewer participants were female in Arm 8A compared with Arms 8B and 5A (48% versus 57% and 65%, respectively). During the study, 421 out of 528 participants (80%) reported ongoing medical conditions. The four most frequently reported conditions, categorized by the MedDRA System Organ Class, were (1) musculoskeletal and connective tissue disorders (35%), (2) vascular disorders (30%), (3) immune system disorders (30%), and (4) metabolism and nutrition disorders (27%). Additionally, fifteen pregnancies were reported during the study.
3.2. Immunogenicity by HBGA-Blocking Antibodies (Primary Objective)
In the one-dose 15/50/0 recipients (Arm 8A), GI.1-specific and GII.4c-specific HBGA-blocking antibodies appeared to persist up to five years post-vaccination. These antibodies increased from baseline to peak at four to eight weeks, then plateaued above baseline after three years (
Figure 2), and showed greater fold changes compared with baseline for GI.1 GMTs than for GII.4c GMTs. This latter difference stemmed from lower baseline GI.1 GMTs, likely reflecting less recent immune exposure and lower prevalence of GI.1 genotypes compared with GII.4 genotypes. Hence, from 3 to 5 years, GI.1 GMTs ranged between 53 (95% confidence interval (95%CI), 40–71) and 60 (95%CI, 46–77; N = 69–97), remaining below the peak GMT of 229 (95%CI, 161–326; N = 81), but approximately 2-fold higher than baseline GMTs of 24 (95%CI, 20–28; N = 105). GII.4c GMTs ranged between 103 (95%CI, 77–138) and 114 (95%CI, 86–152; N = 70–97), below the peak GMT of 623 (95%CI, 372–1042; N = 53), yet consistently above baseline, but by less than 2-fold (70 (95%CI, 53–92); N = 105). After 3 to 5 years, median GI.1-specific titers (122–136) and GII.4c-specific titers (52–70) were also higher compared with their respective baseline median titers of 59 and 15.
The HBGA-blocking GMTs at three to five years were also higher than baseline when excluding data from vaccine recipients considered to have had a natural norovirus infection between two and five years after vaccination (i.e., ≤19% of one-dose 15/50/0 recipients had either a GI.1-like or GII.4-like infection;
Supplementary Figure S1). For recipients of the one-dose 15/50/0 regimen (Arm 8A), the trends in the HBGA-blocking GMTs remained consistent when analyzed by initial trial (i.e., NOR-107, NOR-210, and NOR 204) and by age within NOR-204 (
Supplementary Figure S2). All GI.1-specific HBGA-blocking GMTs at 3 to 5 years were higher than those at baseline, except for 1 GMT (in the 60- to 94-year age group from NOR-204), and GII.4c-specific HBGA-blocking GMTs at 3 to 5 years were also higher than those at baseline.
The trends in the HBGA-blocking GMTs of recipients of the two-dose 15/50/0 (Arm 8B) and the one-dose 15/50/15 (Arm 5A) regimen were similar to those of the one-dose 15/50/0 recipients (
Figure 2). In recipients of the two-dose 15/50/0 regimen, GI.1-specific and GII.4c-specific HBGA-blocking GMTs measured three to five years after dosing were higher than at baseline. For GI.1, GMTs ranged between 69 (95%CI, 51–95) and 82 (95%CI, 60–110; N = 40–62) after 3 to 5 years, compared with 25 (95%CI, 20–32; N = 67) at baseline. For GII.4c, GMTs ranged between 117 (95%CI, 78–174) and 157 (95%CI, 110–223; N = 41–62) after 3 to 5 years, versus 91 (95%CI, 66–127; N = 67) at baseline. In recipients of the 1-dose 15/50/15 regimen (Arm 5A), GI.1 GMTs 3 to 5 years after dosing were higher than at baseline (41 (95%CI, 28–61) to 50 (95%CI, 37–69; N = 31–47) versus 20 (N = 52)). GII.4c GMTs were higher than baseline only at 3 years within the 3-to-5-year period (119 (95%CI, 80–176; N = 31–47) versus 92 (95%CI, 61–141; N = 52)).
3.3. Immunogenicity by Pan-Ig Antibody-Binding Assay (Secondary Objective)
GI.1- and GII.4c-specific pan-Ig-binding antibodies also appeared to persist up to five years after vaccination, similar to what was observed with HBGA-blocking antibodies (
Figure 3). In recipients of the one-dose 15/50/0 regimen (Arm 8A), the magnitude of the fold change after three to five years compared with baseline was greater than two-fold for both GI.1 and GII.4c GMTs. For GI.1, GMTs after 3 to 5 years were 1.7 × 10
3 (N = 71–97), whereas the GMT at baseline was 0.5 × 10
3 (N = 105). For GII.4c, GMTs after 3 to 5 years ranged between 1.4 and 1.7 × 10
3 (N = 71–97), whereas the GMT at baseline was 0.6 × 10
3 (N = 105).
For recipients of the one-dose 15/50/0 regimen (Arm 8A), the trends in the pan-Ig GMTs remained consistent when analyzed by the initial trial and by age in NOR-204. All GI.1 GMTs at 3 to 5 years were higher than those at baseline, and except for 1 GMT (in the 18- to 49-year group from NOR 204), all 3- to 5-year GII.4c GMTs were higher than those at baseline (
Supplementary Figure S3).
The trends in the pan-Ig GMTs were similar when excluding data from vaccine recipients who were considered to have had a natural norovirus infection between two and five years after vaccination (
Supplementary Figure S4).
The trends in the pan-Ig GMTs of recipients of the two-dose 15/50/0 regimen (Arm 8B) and the one-dose 15/50/15 regimen (Arm 5A) were similar to those of the one-dose 15/50/0 recipients (
Figure 3). In recipients of the two-dose 15/50/0 regimen (Arm 8B) and the one-dose 15/50/15 regimen (Arm 5A), all GI.1 GMTs were approximately two-fold higher, and all GII.4 GMTs were less than two-fold higher, respectively, three to five years after dosing, compared with the baseline.
3.4. Antibody-Secreting Cell Responses (Exploratory Objective)
There was evidence of B-cell memory to HIL-214 vaccination three to five years after dosing (
Figure 4). For the 1-dose 15/50/0 recipients (Arm 8A) in the ASC subset, stratified by former trial, all 3- to 5-year GI.1-specific median ASC frequencies, except 1 median (from the 60- to 94-year group from NOR-204), were greater than those at baseline. Similarly, all 3- to 5-year GII.4c-specific ASC frequencies, except 2 medians (from NOR-107 and the 60- to 94-year group from NOR-204), were greater than those at baseline. From 3 to 5 years, GI.1 median ASC frequencies ranged between 0.6 and 2.9 × 10
3 per million ASCs (N = 5–16), compared with baseline median frequencies ranging between 0.4 and 0.8 × 10
3 per million ASCs (N = 5–17). GII.4c median ASC frequencies ranged between 0.4 and 1.0 × 10
3 per million ASCs (N = 5–16), whereas baseline median frequencies ranged between 0.1 and 0.6 × 10
3 per million ASCs (N = 5–17).
3.5. Safety
Although there was no safety objective in the study, life-threatening and fatal SAEs, potential vaccine-related SAEs, potential immune-mediated events, events of medical significance, and any procedure-related medical occurrences were monitored during the follow-up period (1–5 years after vaccination;
Table 3). Overall, there were 26 adverse events reported by 18 participants (3.4%), including 21 SAEs reported by 16 participants, including 6 deaths. One SAE (metastatic renal cell carcinoma) led to the withdrawal of one participant, and it was ultimately fatal. The investigators did not consider that any of the AEs, including SAEs and deaths, were related to the study vaccinations administered in the previous trials. However, one adverse event was causally related to the blood draw in this trial, and this was reported as a mild-intensity post-procedural complication.
4. Discussion
This two- to five-year follow-up Phase 2 study of adult HIL-214 recipients from three previous clinical trials (NOR-107, NOR-210, and NOR-204) identified evidence that norovirus vaccine immunogenicity persisted up to five years, notably marked by HBGA-blocking titers, pan-Ig titers, and ASC frequencies remaining above pre-vaccination baseline values. The analysis was descriptive and focused on the 1-dose 15/50/0 arm, which comprised 105 of the 528 participants recruited. This dosage was selected as the preferred one for adults in two previous trials (NOR-107 and NOR-204). Participants, enrolled at two sites in Belgium and nine sites in the US, were considered immune experienced to norovirus. The mean age at vaccination was 54 years, with 77% of participants aged between 18 and 64 years, 97% identifying as White, and 61% being female. SAEs reported during follow-up were considered unrelated to vaccination and consistent with expectations based on the demographics and prior medical conditions of the study population.
The evidence supporting persistent vaccine immunogenicity was derived from primary and secondary analyses of serum HBGA-blocking titers and pan-Ig titers, respectively. Although no inferential statistics were applied and the GMTs from three to five years post-vaccination were only approximately two-fold or less than two-fold greater than baseline (pre-vaccination), several aspects of the analyses reinforced the study’s main conclusion. These aspects included (i) the GMT relationship identified at the three-, four-, and five-year time points, suggesting that GMTs had plateaued at a steady-state level higher than the pre-vaccination baseline, (ii) the GMT relationship generally held when analyzed with respect to subgroups based on previous trial allocation, (iii) the GMT relationship persisted when data from putatively infected participants were excluded, and (iv) similar GMT relationships were observed with related dosages (two-dose 15/50/0 and one-dose 15/50/15). Additionally, the analysis of a smaller ASC subset suggested that circulating B cells in peripheral blood may have contributed to the sustained production of serum antibodies throughout five years.
The absence of a placebo control group for monitoring long-term changes from baseline titers due to natural infections during the study was a limitation of the analysis. Estimates suggest a norovirus disease rate of approximately 5% of the adult population per year [
13,
14,
15]. The baseline GMTs prior to vaccination reflected immune experience to norovirus, particularly to GII.4-specific over GI.1-specific genotype norovirus strains. The mitigation step to remove data by the final year from up to 19% of vaccine recipients with putative natural GI.1-specific or GII.4-specific norovirus infections inevitably resulted in lower post-vaccination GMTs, as a putative infection was defined by an increase in a GI.1- or GII.4c-specific titer. This mitigation may have biased the results toward underestimating the true difference from baseline, especially with GII.4c-specific GMTs. Nevertheless, as stated above, the adjusted GMTs generally remained above the respective pre-vaccination baselines.
Another limitation was that antibody titers and ASC frequencies (in a smaller subset) in peripheral blood provided only a narrow view of anti-norovirus immunity and an indirect assessment of cellular immune memory [
16]. Nevertheless, it is reasonable to assume that both factors would play a role in an anamnestic response to norovirus infection. Moreover, HBGA-blocking antibodies (the primary endpoint measure) may be clinically relevant because these antibodies potentially neutralize norovirus infection of enterocytes in the gut, and the incidence of norovirus gastroenteritis is lower in individuals with mutations that prevent the synthesis of HBGA [
11,
17,
18,
19,
20]. However, a clear association with responses to vaccination and the prevention of norovirus gastroenteritis remains to be identified [
9,
21].
5. Conclusions
This study provided evidence that in adults, the immunogenicity of a single dose of the norovirus vaccine HIL-214 persisted up to five years. This was indicated by HBGA-blocking titers, pan-Ig titers, and ASC frequencies remaining above pre-vaccination baseline values.
Supplementary Materials
The following supporting information can be downloaded at:
https://www.mdpi.com/article/10.3390/vaccines13010082/s1. Table S1: Demographic characteristics in the FAS, PPS and ASC subset; Figure S1: HBGA-blocking GMTs without data from participants putatively infected with norovirus; Figure S2: HBGA-blocking GMTs in recipients of a single dose of 15/50/0 by preceding trial; Figure S3: Pan-Ig GMTs in recipients of a single dose of 15/50/0 by preceding trial; Figure S4: Pan-Ig GMTs without data from participants putatively infected with norovirus.
Author Contributions
Conceptualization, J.P.C. and A.B.; methodology, G.L.-R., R.L.A., J.P.C. and A.B.; formal analysis, I.E. and A.B.; investigation, G.L.-R. and R.L.A.; resources, J.P.C., I.E. and A.B.; data curation, I.E. and A.B.; writing—original draft preparation, A.B.; writing—review and editing, all authors; supervision, J.P.C. and A.B.; project administration, J.P.C., I.E. and A.B.; funding acquisition, J.P.C. and A.B. All authors have read and agreed to the published version of the manuscript.
Funding
The trial was sponsored and funded by Takeda Vaccines, Inc. (MA, USA). Scientific writing in the preparation of the manuscript was funded by HilleVax, Inc. (Seattle, WA 98101, USA).
Institutional Review Board Statement
The trial protocol, protocol amendments, informed consent form (ICF), and other information that required approval were reviewed and approved by the institutional review board (IRB) of each clinical site.
Informed Consent Statement
Written informed consent was obtained from each participant prior to performing any trial-specific procedures.
Data Availability Statement
The clinical study report (NOR-213) and associated data on which this manuscript is based are available upon request from Takeda Pharmaceuticals International AG, Switzerland.
Acknowledgments
The authors thank the participants of the NOR-213 clinical study. The authors thank Frank Baehner and Taisei Masuda (former employees of Takeda, Switzerland, at the time NOR-213 was underway), Nancy Le Cam (consultant for Takeda at the time NOR-213 was underway), and John Treanor (the principal investigator of NOR-204 at the Department of Medicine, University of Rochester Medical Center, Rochester, NY, USA) for their contributions to the design and conduct of the clinical trials feeding NOR-213. The authors also thank Frances Chen (Takeda Vaccines Inc. USA) for data management and statistical support in completing the NOR-213 clinical study report on which this manuscript is based. Matthew Morgan (MG Science Communications, Belgium) provided scientific writing services.
Conflicts of Interest
At the time of this report, G.L.R. is (or has been in the past three years) a consultant for Curevac, HilleVax, ICON Genetics, Minervax, Novavax, Osivax, Quantoom, and Sumitomo Pharma, Virometix. R.A. has received research support from Takeda Vaccines, Inc. and HilleVax, Inc., and at the time of this report serves as a consultant to HilleVax, Inc. At the time of this report, I.E. is a full-time employee of Takeda Vaccines and holds Takeda stock. At the initiation and running of the study, J.K. and A.B. were full-time employees of Takeda Vaccines, and at the time of this report, A.B. is a full-time employee of HilleVax Inc.
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Figure 1.
Schematic description of participant disposition for all eligible and enrolled participants entered in the follow-up study from the initial trials NOR-107, NOR-210, and NOR-204. Participants from NOR-210 and NOR-204 entered the follow-up study at the beginning of Year 2 (i.e., one year after vaccination), whereas participants from NOR-207 entered at the beginning of Year 3. The disposition is shown for (A) the full analysis set (FAS) for the entire study population and (B) for the FAS for Arms 5A, 8B, and 8A. The light-grey boxes indicate participants who discontinued, and the reasons for discontinuation. The numbers in the light-grey boxes represent cumulative totals, in accordance with the directions of the arrows. PPS = per-protocol set.
Figure 1.
Schematic description of participant disposition for all eligible and enrolled participants entered in the follow-up study from the initial trials NOR-107, NOR-210, and NOR-204. Participants from NOR-210 and NOR-204 entered the follow-up study at the beginning of Year 2 (i.e., one year after vaccination), whereas participants from NOR-207 entered at the beginning of Year 3. The disposition is shown for (A) the full analysis set (FAS) for the entire study population and (B) for the FAS for Arms 5A, 8B, and 8A. The light-grey boxes indicate participants who discontinued, and the reasons for discontinuation. The numbers in the light-grey boxes represent cumulative totals, in accordance with the directions of the arrows. PPS = per-protocol set.
Figure 2.
GI.1-specific and GII.4c-specific HBGA-blocking geometric mean titers (GMTs; left and right graphs, respectively) over a five-year period from prior to dosing (Week 0, W0) in the preceding trials to the end of the present follow-up study (Year 5, Y5) in the per-protocol set (PPS) without data from participants putatively infected with norovirus (with either a GI.1-like or GII.4-like genotype and identified by a ≥4-fold increase in antibody titer at a subsequent visit during the follow-up period). Three dosage regimens are shown: (i) one dose of 15/50/0 (either at W0 or W4; grey arrows), (ii) two doses of 15/50 (at W0 and W4; black arrows), and (iii) one dose of 15/50/15 at W4 (black arrows). GMTs and 95% confidence intervals are represented by colored round symbols (and value above the plot) and error bars, respectively. Medians, 25 and 75 percentiles, and minimum and maximum values are represented by grey box and whisker plots.
Figure 2.
GI.1-specific and GII.4c-specific HBGA-blocking geometric mean titers (GMTs; left and right graphs, respectively) over a five-year period from prior to dosing (Week 0, W0) in the preceding trials to the end of the present follow-up study (Year 5, Y5) in the per-protocol set (PPS) without data from participants putatively infected with norovirus (with either a GI.1-like or GII.4-like genotype and identified by a ≥4-fold increase in antibody titer at a subsequent visit during the follow-up period). Three dosage regimens are shown: (i) one dose of 15/50/0 (either at W0 or W4; grey arrows), (ii) two doses of 15/50 (at W0 and W4; black arrows), and (iii) one dose of 15/50/15 at W4 (black arrows). GMTs and 95% confidence intervals are represented by colored round symbols (and value above the plot) and error bars, respectively. Medians, 25 and 75 percentiles, and minimum and maximum values are represented by grey box and whisker plots.
Figure 3.
GI.1-specific and GII.4c-specific pan-Ig geometric mean titers (GMTs; left and right graphs, respectively) over a five-year period from prior to dosing (Week 0, W0) in the preceding trials to the end of the present follow-up study (Year 5, Y5) in the per-protocol set (PPS). Three dosage regimens are shown: (i) one dose of 15/50/0 (either at W0 or W4; grey arrows), (ii) two doses of 15/50/0 (at W0 and W4; black arrows), and (iii) one dose of 15/50/15 at W4 (black arrows). GMTs and 95% confidence intervals are represented by colored round symbols (and value above the plot) and error bars, respectively. Medians, 25 and 75 percentiles, and minimum and maximum values are represented by grey box and whisker plots. Note, the GMTs in the figure are expressed in a scientific notation that includes a 103 multiplier.
Figure 3.
GI.1-specific and GII.4c-specific pan-Ig geometric mean titers (GMTs; left and right graphs, respectively) over a five-year period from prior to dosing (Week 0, W0) in the preceding trials to the end of the present follow-up study (Year 5, Y5) in the per-protocol set (PPS). Three dosage regimens are shown: (i) one dose of 15/50/0 (either at W0 or W4; grey arrows), (ii) two doses of 15/50/0 (at W0 and W4; black arrows), and (iii) one dose of 15/50/15 at W4 (black arrows). GMTs and 95% confidence intervals are represented by colored round symbols (and value above the plot) and error bars, respectively. Medians, 25 and 75 percentiles, and minimum and maximum values are represented by grey box and whisker plots. Note, the GMTs in the figure are expressed in a scientific notation that includes a 103 multiplier.
Figure 4.
GI.1-specific and GII.4c-specific median antibody-secreting cell (ASC) frequencies per million antigen-secreting cells (ASCs; left and right graphs, respectively) over a five-year period from prior to dosing (Week 0, W0) in the preceding trials to the end of the present follow-up study (Year 5, Y5) for recipients of a single dose of 15/50/0 (Arm 8A) at W4 (black arrows) in the ASC subset. Medians and minimum and maximum values are represented by colored round symbols (and value above the plot) and error bars, respectively. * The maximum value reported at this time point was 2.3 × 106 and hence potentially erroneous (>million GI.1-specifc ASCs per million ASCs). Note, the median ASC frequencies in the figure are expressed in a scientific notation that includes a 103 multiplier. Note also that blank entries in the graphs reflect that sampling was not performed at those time points (i.e., in NOR-107).
Figure 4.
GI.1-specific and GII.4c-specific median antibody-secreting cell (ASC) frequencies per million antigen-secreting cells (ASCs; left and right graphs, respectively) over a five-year period from prior to dosing (Week 0, W0) in the preceding trials to the end of the present follow-up study (Year 5, Y5) for recipients of a single dose of 15/50/0 (Arm 8A) at W4 (black arrows) in the ASC subset. Medians and minimum and maximum values are represented by colored round symbols (and value above the plot) and error bars, respectively. * The maximum value reported at this time point was 2.3 × 106 and hence potentially erroneous (>million GI.1-specifc ASCs per million ASCs). Note, the median ASC frequencies in the figure are expressed in a scientific notation that includes a 103 multiplier. Note also that blank entries in the graphs reflect that sampling was not performed at those time points (i.e., in NOR-107).
Table 1.
Arm assignment by former trial and HIL-214 composition and doses.
Table 1.
Arm assignment by former trial and HIL-214 composition and doses.
Arm | HIL-214 Components (µg) | Doses | Number of Participants from Former Trial b | Total Number of Participants |
---|
GI.1 | GII.4c | Al(OH)3 | MPL | NOR-107 | NOR-210 | NOR-204 |
---|
1A | 15 | 15 | 500 | 50 | 1 | 25 | | | 25 |
2A | 15 | 50 | 500 | 50 | 1 | 19 | | | 19 |
3A | 50 | 50 | 500 | 50 | 1 | 27 | | | 27 |
4A | 15 | 15 | 500 | 15 | 1 | 27 | | | 27 |
5A a | 15 | 50 | 500 | 15 | 1 | 23 | | 29 | 52 |
6A | 50 | 50 | 500 | 15 | 1 | 27 | | | 27 |
7A | 15 | 15 | 500 | 0 | 1 | 25 | | | 25 |
8A a | 15 | 50 | 500 | 0 | 1 | 28 | 24 | 53 | 105 |
9A | 50 | 50 | 500 | 0 | 1 | 22 | | | 22 |
10A | 50 | 150 | 500 | 0 | 1 | 28 | | | 28 |
11A | 15 | 50 | 167 | 0 | 1 | 21 | | | 21 |
5B | 15 | 50 | 500 | 15 | 2 | | | 35 | 35 |
8B a | 15 | 50 | 500 | 0 | 2 | 25 | | 42 | 67 |
10B | 50 | 150 | 500 | 0 | 2 | 24 | | | 24 |
11B | 15 | 50 | 167 | 0 | 2 | 24 | | | 24 |
Table 2.
Demographic characteristics in Arms 5A, 8B, and 8A of the PPS.
Table 2.
Demographic characteristics in Arms 5A, 8B, and 8A of the PPS.
Category | 5A: 15/50/15, 1-Dose | 8B: 15/50/0, 2-Dose | 8A: 15/50/0, 1-Dose |
---|
| | N = 52 | N = 67 | N = 105 |
---|
| | Mean (SD) |
Period from 1st Dose to Last Visit (years) | 4.9 (0.5) | 4.9 (0.4) | 4.9 (0.4) |
Age (years) | Overall | 62.3 (16.8) | 63.6 (19.4) | 53.9 (21.2) |
| | | n (%) | |
Age range: | 18–64 | 30 (57.7) | 28 (41.8) | 72 (68.6) |
(years) | 65–84 | 17 (32.7) | 29 (43.3) | 22 (21.0) |
| ≥85 | 5 (9.6) | 10 (14.9) | 11 (10.5) |
Female | 34 (65.4) | 38 (56.7) | 50 (47.6) |
Ethnicity: | Not Reported | 23 (44.2) | 25 (37.3) | 28 (26.7) |
| Not Hispanic or Latino | 28 (53.8) | 39 (58.2) | 69 (65.7) |
| Hispanic or Latino | 1 (1.9) | 3 (4.5) | 8 (7.6) |
Race | White | 51 (98.1) | 64 (95.5) | 94 (89.5) |
| Black or African American | 1 (1.9) | 3 (4.5) | 8 (7.6) |
| Asian | 0 (-) | 0 (-) | 1 (1.0) |
| Native Hawaiian or Other Pacific Islander | 0 (-) | 0 (-) | 1 (1.0) |
| Multiracial a | 0 (-) | 0 (-) | 1 (1.0) |
Table 3.
Adverse events during Year 2 to Year 5 after primary vaccination.
Table 3.
Adverse events during Year 2 to Year 5 after primary vaccination.
| FAS (N = 528) |
---|
| Events, ne | Participants, n (%) |
---|
Any Adverse Event | 26 | 18 (3.4) |
| 1 | 1 (0.2) |
| 0 | 0 (-) |
| 1 | 1 (0.2) |
| 6 | 3 (0.6) |
| 19 | 14 (2.7) |
| 1 | 1 (0.2) |
Potential Immune-Mediated Event | 6 | 5 (0.9) |
| 0 | 0 (-) |
| 0 | 0 (-) |
Serious Adverse Events (SAEs) | 21 | 15 (2.8) |
| 0 | 0 (-) |
| 1 | 1 (0.2) |
Deaths (All Unrelated to Prior Trial Vaccines) | 6 | 6 (1.1) |
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