Methods

SARS-CoV-2 seronegative and unvaccinated adults were randomly assigned (5:5:2) to receive 25μg or 50μg of SpFN/ALFQ or saline placebo intramuscularly at days 1 and 29, with, an optional open-label third vaccination at day 181. Local and systemic reactogenicity, adverse events, binding (BAb) and neutralizing antibodies (NAb) and antigen-specific T-cell responses were quantified. For safety analyses, exact 95% Clopper-Pearson confidence intervals (CIs) for the probability of any incidence of each reported unsolicited adverse event was computed for each group. For immunogenicity results, CIs for binary variables were computed using the exact Clopper-Pearson methodology, while CIs for geometric mean titer were based on 10,000 empirical bootstrap samples. Post hoc, paired one-sample t-tests were used to assess the increase in mean log-10 Nab titers between days 29 and 43 (post-second vaccination) for the primary SARS-CoV-2 targets of interest.

Findings

Twenty-nine participants were enrolled between April 7, 2021 and June 29, 2021. Neutralizing antibody responses peaked at day 43, two-weeks post second dose. Neutralization activity against multiple Omicron subvariants decayed more slowly than against the D614G or Beta variants through five months after second vaccination. CD4+ T-cell responses were elicited four-weeks after the first dose and were boosted after a second dose of SpFN/ALFQ. Neutralizing antibody titers against early Omicron subvariants and clade 1 sarbecoviruses were detectable after two immunizations and peaked after the third immunization. Neutralizing antibody titers against XBB 1.5 were detected after three vaccinations. Passive IgG transfer from vaccinated volunteers into hamsters controlled replication of SARS-CoV-1 post challenge.

Interpretation

SpFN/ALFQ was well-tolerated and elicited robust and durable BAb and NAb titers against all broad panel of SARS-CoV-2 variants and other sarbecoviruses.

Funding

US Department of Defense, Defense Health Agency.

Study Design

This single-site phase 1, randomized, double-blind, placebo-controlled, clinical trial was designed to address the primary and secondary objectives of tolerability and humoral immunogenicity according to increasing immunogen dosage (25μg, 50μg) with a constant dose (0·5mL) of the ALFQ adjuvant across groups.

Participants

Twenty-nine participants were enrolled between April 6, 2021 and June 29, 2021 and followed through January 2023 (Figure 1). Study visits were conducted at the Clinical Trial Center, Walter Reed Army Institute for Research (WRAIR). The study protocol, was approved by the WRAIR Institutional Review Board. Written informed consent was obtained from all participants. This clinical trial is registered atClinicalTrials.gov (NCT04784767).

Randomisation and Masking

Participants were randomized into groups to active vaccine or placebo at a ratio of 5:1 in a blinded manner. Blinded vaccination occurred on day 1 and day 29 with an optional, open-label third vaccination on day 181 for participants randomized to receive the vaccine. Participants and study staff were unblinded after all enrolled participants had completed the day 57 visit.

Vaccine

SpFN was produced by linkingHelicobacter pylori ferritin to the C-terminal region of the prefusion stabilized ectodomain (residues 12-1158) of the SARS-CoV-2 S protein through genetic fusion. The immunogen was expressed, purified and characterized as previously described (14). Expi293F HEK cells (ThermoFisher) were transiently transfected with plasmid DNA pCoV1B-06-PL (Aldeveron) using Turbo293 transfection reagent (Speed Biosystems). Clarified cell culture harvest was treated with benzonase treated, ultrafiltered/diafiltered, purified by Fractogel DEAE (Millipore) chromatography and a CaptoCore 400 (Cytiva) polishing step, followed by a second ultrafiltration/diafiltration and final sterile filtration at the WRAIR Pilot Bioproduction Facility. Final drug product vialed at 100μg/mL and stored at −20°C.

ALFQ is a unilamellar liposome that contains saturated phospholipids, cholesterol, monophosphoryl lipid A and the saponin, QS-21. It is comprised of dimyristoyl phosphatidylcholine, dimyristoyl phosphatidylglycerol, cholesterol, and synthetic monophosphoryl lipid A (3D-PHAD) (Avanti Polar Lipids) and QS-21 (Desert King). ALFQ was formulated as previously described (14,18). The 3D-PHAD^® dose was 200μg and the QS-21 dose was 100μg. Although the immunogen dose varied by study group, the adjuvant dose remained constant (0·5mL).

Study Procedures

Participants were screened for active or previous SARS-CoV-2 infection at every visit through nasopharyngeal swabs using a real-time RT-PCR qualitative nucleic acid amplification test (NAAT) assay (Panther Fusion SARS-CoV-2, Hologic), serology, and questionnaire.

The immunogen, SpFN, and adjuvant, ALFQ, were mixed in the pharmacy and administered within four hours of preparation. Normal saline was used for placebo administration. Local and systemic AEs and safety laboratory values were graded by the Toxicity Grading Scale for Healthy Adult and Adolescent Volunteers Enrolled in Preventive Vaccine Clinical Trials (19). All other AEs were graded according to a protocol-defined severity scale. Results through day 209 are reported here.

Outcomes

The primary objectives of this study are the safety and reactogenicity of 25μg and 50μg of SpFN/ALFQ and the humoral immune response at day 43, two weeks after the second injection.

Assessment of Binding Antibody Responses

SARS-CoV-2 seronegative status was determined using a total IgM, IgA, IgG nucleocapsid antibody screen, Platelia SARS-CoV-2 Total Ab Assay (BioRad Laboratories, Inc^®). Binding antibody responses against the prefusion-stabilized spike (Spike) (20), receptor binding domain (RBD), andH. pylori ferritin were quantitated as previously described using a validated solid-phase electrochemiluminescence S-binding IgG immunoassay (ECLIA) (21).

Assessment of Neutralizing Antibody Responses

Neutralization of SARS-CoV-2 D614G, Delta, Beta and Omicron BA·1 pseudoviruses were performed at Duke University based on a validated adaptation of the assay utilized by the NIH Vaccine Research Center (22). The pseudovirus assays of neutralization of Omicron subvariants BA·1, BA·2, BA·2·5, BA·2·75, BA·5. BQ·1·1., and XBB.1.5, as well as the more closely related clade 1b sarbecoviruses RaTG13, Pangolin-GX-P2V, Pangolin-GX-P5L, and the more distant clade 1a viruses, SARS-CoV Urbani, SARS-CoV Frankfurt, WIV1, and SHC014 were performed at the NIH Vaccine Research Center. Antigenic cartography maps were constructed as previously described (23) using the R package Racmacs (https://acorg.github.io/Racmacs/, version 1.1.35) to visualize the relative neutralization sensitivity and immune escape of four SARS-CoV-2 variants and seven sarbecovirus species. Data points represent the different pseudoviruses tested in the neutralization assay and each participant’s serum. The distance between each serum and pseudovirus pair was calculated from a titer reduction (log2) against the virus that had the highest titer. Multidimensional Scaling was used to arrange points to minimize Euclidian distances. Maps were generated from the neutralization data of the ten individuals who received three vaccine doses. Neutralization of Middle East respiratory syndrome coronavirus (MERS-CoV) was assessed by a similar pseudovirus neutralization assay at WRAIR (Supplementary Methods).

Cell-Mediated Immunity

CD4+ and CD8+ T-cell responses against the SARS-CoV-2 Spike were quantified by flow cytometry with a validated intracellular cytokine staining assay (24). Overall response to SARS CoV-2 was defined as the sum of the background subtracted responses to each individual pool. (Supplementary Table S1. Cellular polyfunctionality was assessed by COMPASS analysis (25).

Passive IgG Administration to Syrian Golden Hamsters

To assess breadth of cross-protection, IgG antibodies from pooled plasma from placebo recipients and vaccinees receiving three SpFN vaccinations was infused into Syrian Golden hamsters (SGH) prior to SARS-CoV-1 Urbani challenge as described inSupplementary Methods.

Statistical Analysis

Safety analyses were conducted on all participants who received at least one vaccination. The frequency of all unsolicited AEs, categorized by MedDRA^® system organ class, was summarized by group and severity, and the incidence was described by relationship to vaccination. Exact 95% Clopper-Pearson confidence intervals (CIs) for the probability of any incidence of each reported unsolicited AE (by MedDRA^® preferred term) was computed for each group. Serious AEs, medically-attended AEs, new-onset chronic medical conditions, potentially immune-mediated diseases or suspected unexpected serious adverse reactions were summarized as well. The maximum severity of solicited reactogenicity events was summarized by symptom and group, for the reactogenicity period (8 days) post-each dose and post-any dose. Clinical laboratory results were summarized by severity, study day, and group.

Antibody response rates are the proportion of responses greater than or equal to the laboratory-defined, target-specific threshold for positive response for binding antibody titers, or seroconversion. Seroconversion for Nab titers is defined by having an undetectable baseline titer and either a post-vaccination titer greater than the lower limit of detection (LLOD) or having a detectable response at baseline and at least a 4-fold rise post-vaccination, CIs for binary variables were computed using the exact Clopper-Pearson methodology, while CIs for GMT were based on 10,000 empirical bootstrap samples. Post hoc, paired one-sample t-tests were used to assess the increase in mean log-10 Nab titers between days 29 and 43 (post-second vaccination) for the primary SARS-CoV-2 targets of interest.

Sensitivity analyses for responses were completed to make qualitative comparisons against results from the full BAb and NAb immunogenicity population. These excluded participants reporting protocol deviations for the receipt of EUA or approved COVID-19 vaccinations (Supplementary Table S2 andS3), and included only participants who received all three vaccinations. Lung inflammation scores from SGH post SARS-CoV-1 Urbani challenge were analyzed with via unpaired t-test.

Role of Funder

The funder had no role in the study design, data collection, data analysis, data interpretation, or writing of the statistical report. Data cleaning and analysis were conducted by a third party contract research organization (The EMMES Company, LLC).

Study Participants

Participants had a mean age of 36·7 years [Min=20, Max=55, standard deviation=11] and mostly male (72·4%), White (51·7%) or Black (34·5%). Baseline characteristics were qualitatively similar between vaccination groups (Table 1). Fifty-five individuals were assessed for eligibility with 3 eligible but not enrolled and 23 not eligible for enrollment (Figure 1). All 29 randomized participants received the first injection, twenty-eight received the second injection, and ten received the third injection. Within each dose group, twenty participants received two injections with 25μg SpFN/ALFQ at days 1 and 29 and three participants received 50μg SpFN/ALFQ at the same time points. One participant in the 50μg group received SpFN/ALFQ only on day 1 due to a new-onset grade 1 neutropenia that precluded administration of a booster dose, and was subsequently lost to follow-up (LTFU). Five participants received a saline placebo. After unblinding, 10 participants (9 in the 25μg and 1 in the 50μg group) received an optional, open-label third dose of SpFN/ALFQ at Day 181. These 10 participants remained naïve to infection and had not yet received a COVID-19 vaccine grantedan Emergency Use Authorization COVID-19 by the US Food and Drug Administration. Nine participants (2 placebo, 3 recipients of 25μg, and 3 recipients of 50μg of SpFN/ALFQ) either decided to terminate early from the study or were LTFU between days 57 and 209, after the follow-up period for the primary and secondary immunologic endpoint analysis. None of the early terminations or LTFU were due to SpFN/ALFQ vaccination. One participant was excluded after the second vaccination due to undisclosed receipt of an EUA vaccine prior to enrolling in the trial but was monitored through the end of the trial for safety and included in the immunogenicity analysis population after day 43. Twelve participants (9 in 25μg group, 0 in 50μg group, and 3 in placebo) who either reported receipt of an EUA or approved COVID-19 vaccine prior to day 181 were included in the primary immunogenicity analysis after two vaccinations. These participants were excluded from further vaccination, but were followed for safety for the duration of the trial.

Safety

No participants experienced any adverse events of special interest (AESI), related or unrelated SAEs or other significant AEs that precipitated study withdrawal. A formal statistical analysis between groups was not possible given the small number of participants in the 50μg group who received at least two vaccinations (n=3/4).

Forty-six unsolicited AEs were reported (33 among 16 participants in the 25μg group, 7 among 3 participants in the 50μg group, and 6 among 4 participants in the placebo group), 11 of which were possibly related to study vaccination (9 mild and 1 moderate reported among 8 participants in the 25μg group, 1 mild in the 50μg group) (Figure 2). No severe unsolicited AEs were reported in any group, and 10 moderate AEs were reported (6 among 4 participants in the 25μg group, 2 among 2 participants in the 50μg group, and 2 among 2 participants in the placebo group).

Most participants reported at least one solicited event after each study vaccination, with more moderate events reported after the second and third doses than the first. Overall, 88% (n=21/24) of participants who received the vaccine reported one or more solicited AEs of any kind following either the first, second or third dose. The same proportion of participants (88% (n=21/24)) reported at least one local reactogenicity AE (50% (n=12/24) mild; 33% (n=8/24) moderate; 4% (n=1/24) severe) (Figure 1A). Systemic AEs were as common as local solicited AEs (88% (n=21/24) overall; 25% (n=6/24) mild; 58% (n=14/24) moderate; 4% (n=1/24) severe)) (Figure 1b). Two participants, one in each active vaccination group, reported severe reactogenicity events (severe fever post third vaccination in the 25μg group, severe pain post second vaccination in the 50μg group) that both resolved within 72 hours without sequelae. Injection site pain was the most common local AE (88% (n=21/24)), while the most common systemic AEs were myalgia (71% (n=17/24)), fatigue (71% (n=17/24)), headache (58%, (n=14/24)) and rigors (58%, (n=14/24)). Rigors and fever were more commonly reported after the second vaccination. Both fatigue and headache were reported by 40% and 80%, respectively, of participants not in placebo and irrespective of dose group. Collectively, systemic reactogenicity events were self-limiting and resolved within a few days without intervention.

Abnormalities in safety laboratory parameters were infrequent, mostly mild in severity and all interpreted as unrelated to vaccination. Abnormal hemoglobin values were most commonly reported but only mild in severity. One participant in the 50μg group had mild neutropenia at baseline, meeting inclusion criteria, which increased post first vaccination resulting in study discontinuation.

Immunogenicity

Binding antibody IU/mL titers against SARS-CoV-2 Spike and RBD proteins were detected at all post-vaccination time points and increased substantially in the active vaccine groups after first vaccination and were boosted after second vaccination (Figure 3A and3B). The GMT against SARS-CoV-2 Spike protein was 1·4 (95% CI: 0·8-2·8) in the 25μg group and 2·2 (1·1-9·7) in the 50μg group at baseline and increased by day 43 after second vaccination to 7100.2 (5591·7-9146·8) in the 25μg group and 2090·5 (246·8-9187·3) in the 50μg group. Binding antibodies against SARS-CoV-2 Spike declined minimally by day 181. Binding antibody IU/mL titers against SARS-CoV-2 RBD were consistent with those observed against SARS-CoV-2 Spike.

BAb IU/mL titers against SARS-CoV-2 Spike among participants who received a third vaccination (n=9 for 25μg dose and n=1 for 50μg dose) increased two-weeks post-boost at day 195 (13368·1, 7590·1-23243·1 in the 25μg group) and day 209 (11167·3, 6502·8–20023·1) with 100% response rates. There was no detectable antibody against SARS-CoV-2 nucleocapsid (N) protein at any time point for either active vaccine group. Results of the sensitivity analysis comparing the impact of EUA vaccination after two doses of SpFN/ALFQ versus three vaccinations with SpFN/ALFQ on the breadth of BAb responses are provided inSupplementary Table S2 and demonstrated no qualitative difference. There were antibodies detected againstH. pylori ferritin in each of the vaccine groups subsequent to the vaccinations, however, there were no responses against either human ferritin light chain or heavy chain (Supplementary Figure S1).

Neutralizing antibody responses against the SARS-CoV-2 D614G variant, Beta B·1·351, Delta B·1·617·2, and Omicron B·1·1·529 were assessed in available serum samples for all 29 enrolled participants, from baseline through Day 181 (Figure 4A and4B). After the first two vaccinations with the 25μg dose, responses against both SARS-CoV-2 D614G and Delta B·1·617·2 were robust and exhibited similar qualitative patterns as described above for binding antibody responses, with an increase in GMTs from 6·4 (5·0-9·6) for Alpha D614G and 11.8 (7·3-21·3) for Delta at baseline to 134·5 (D614G, 73·4-247·8) and 123.4 (Delta, 55·8 - 268·8), respectively, at day 29, increasing to 8542·9 (D614G, 6396·9 - 11106·8) and 1640.0 (Delta, 1203·1 -2214·2) at two weeks (day 43) after the second vaccination. At this time point, responses against SARS-CoV-2 Beta B.1.351 (264·5, 185·5-344·6) mutation and Omicron B·1·1·529 (132·0, 78·3 – 225·8) were observed, however, at a lower magnitude than for D614G and Delta. Post hoc Wilcoxon signed-rank tests of the per-participant increase in titers from Day 29 to Day 43 (i.e. after the second vaccination) were statistically significant in the 25μg group for all strains tested (D614G, Beta B.1.351, Delta, and Omicron BA1; p<0.001 for each).

For the 50μg group, similar qualitative patterns to the 25μg group were observed with the following geometric mean IC₅₀ titer estimates by variant: D614G (day 29: 170·7, 36·7-794·8, d43:1835·0, 122·9-11407·5), Beta B·1·351 (d29: 30·6; 8·4 – 138·6, d43: 126·6, 14·8-385·7), Delta B·1·617·2 (d29: 76·8, 27·0-225·2, d43: 523·7; 66·7 – 2329·4), Omicron B·1·1·529 (d29: 11·5, 5·0 - 60·1, d43: 57·2, 12·7 - 223·0). NAb responses for D614G were observed two weeks (day 195) after the third vaccination (25μg group: 7867·0, 4115 – 13703·8), which was consistently observed across the variants.

A sensitivity analysis among the participants who received a third study vaccination, excluding observations after reported protocol deviations due to receipt of non-study COVID-19 vaccination, was performed (Supplementary Table S3). While the further-reduced sample sizes (9 in the 25μg and 1 in the 50μg group) reduced power for quantitative comparisons, NAb GMT estimates after excluding those participants were similar prior to Dose 3 and higher post-Dose 3.

All participants showed a robust neutralization antibody response against SARS-CoV-2 D614G at day 43 with 7 participants exhibiting titers greater than 10000 (Figure 4B). Against the Delta variant, half of the participants had titers around 5000 and the rest were somewhat lower. Against Beta, most of the titers were around 1000 at day 43. The response against Omicron BA·1 was more modest with titers ranging from 76·8 to 227·7 for the 25μg group at day 43. The titers against each of these SARS-CoV-2 variants decreased at Day 181 relative to Day 43 in all participants. Nine participants who received a third immunization demonstrated an increase against D614G at the day 195 time point following the third immunization that matched the day 43 levels. For Delta, Beta and Omicron BA·1, the day 195 titers exceeded the day 43 levels in 3, 8 and 7 participants, out of 9, respectively. This increase in neutralizing titers is most striking against Omicron BA·1 where the day 195 values are 1324·1 to 4696·9 (Figure 4B).

Neutralizing antibody responses against other sarbecoviruses are visualized inFigure 4C and4D with a heatmap of reciprocal neutralization titers (ID₅₀), of participants that received the third vaccination on day 181, on day 43, day 181 and day 195 (Figure 4EF). Remarkably, detectable neutralization titers against SARS-CoV-2 XBB 1.5 was detected after three vaccinations (Figure 4D). The sarbecoviruses and SARS-CoV-2 variants and subvariants are presented according to a phylogenetic tree generated using their respective Spike protein amino acid sequence; this is matched to the Spike used in the pseudovirus neutralization assays (Figure 4E-F).

Figure 4F shows neutralization titers against SARS-CoV-2 Omicron sublineages and more distantly related sarbecoviruses from clades 1a and 1b (Supplementary Table S4). Neutralizing antibody responses at day 43 were robust in all participants against RaTG13, the virus most closely related to SARS-CoV-2. The titers were the most modest against the two SARS-CoV variants. The responses against the other viruses were somewhat higher, around 1000, for the rest of the viruses tested. As seen for the variant inFigure 4B, titers dropped by the second time point, but increased after the third immunization reaching levels 16·24 to 19·63-fold higher than after day 43. For the more distantly related WIV1 and SHC014 pseudoviruses the neutralizing titers were intermediate. There was no detectable neutralization of MERS-CoV (Supplementary Table S5).

The half-life (days) of Nab against D614G, Beta, Delta, and Omicron subvariants BA·1, BA·2, BA·2·75, BA·5, and BQ·1·1, from day 43 through day 181 are shown inSupplementary Table S6. For both the 25μg and 50μg doses, there was an inverse qualitative relationship between the half life and peak neutralization titers at day 43. For the 25μg dose, the half-life was 46·85 and 46·45 days against D614G and Delta, respectively. Responses against Beta, Omicron (BA·1), and the other Omicron subvariants had lower rates of decay. For the four participants in the 50μg dose, the decay rate was less, compared to the 25μg group, against the four SARS-CoV-2 variants.

Passive transfer of purified IgG from individuals who received three doses of SpFN/ALFQ controlled replication of SARS-CoV-1 Urbani strain in the Syrian golden hamsters (Supplementary Figure S2). Lung inflammation was significantly reduced in hamsters receiving IgG from SpFN vaccinees relative to PBS (p=0.031) or control IgG (p=0.014) (Supplemental Figure S3AB).

Antigenic cartography demonstrated that following two vaccinations, responses clustered closest to the WA-1 variant, as expected given that the vaccine insert corresponded to the ancestral D614 sequence of SARS-CoV-2 (Supplemental Figure 4A). Omicron was the most distant with a median 100-fold lower neutralizing antibody titer (−6·69 on the log2 scale), reflecting that Omicron B·1·1·529 was the most genetically distant SARS-CoV-2 variant tested and the most resistant at this timepoint (Supplementary Table S7). Following the third vaccination, an increase in neutralization titers against Beta, Omicron and Delta reduced the antigenic distance relative to D614G with the median fold difference reduced to 1·85 (−0·89 in log2), 3·34 (−1·74 in log2) and 3·71 (−1·89 in log2) for Beta B·1 ·351, Omicron B·1·1·529 and Delta B·1·617·2 respectively. A similar pattern was observed when comparing generated antibodies to different sarbecoviruses (Supplemental Figure 4B). Responses were centered around the RaTG13 strain, which is closely related to SARS-CoV-2. After three vaccinations, antigenic distances were reduced, indicative of increased neutralization breadth.

Spike-specific CD4+ T-cells expressing IFN-γ and/or IL-2, considered the primary cytokine mediators of a T helper type 1 (Th1) response, were detected in 88% of participants after the first dose in the 25μg group with a median magnitude of 0·4% of CD4+ T-cells (Supplemental Figure 5A). The response rate increased to 100% after the second dose with a marked increase in the frequency to a median above 1%. There was a similar pattern for the 50μg group, but there were only data available for three participants after the second dose. One placebo participant had a positive response detected at baseline that was consistently detected at each post-vaccination time point. This response was only detected to the Spike-2 subunit and not Spike-1 (data not shown).

This pattern and the presence at baseline suggest a cross-reactive response to another coronavirus. CD4+ T-cells expressing Th2 cytokines (IL-4, IL-5, IL-13) were only detected after the second dose in the 25μg group with a median magnitude of just above 0·05%, more than 10-fold lower than the Th1-type response (Supplemental Figure 5B). Spike-specific CD8+ T-cells were not detected in any group. Spike-specific CD4+ T-cells were polyfunctional, with some cells co-expressing up to five functional markers (Supplementary Figures S6 andS7).

Panel: Research in Context.

Walter Reed Army Institute for Research

Beza Gebrehana, B.S., Melissa E. Greenleaf, BSN., Melinda J. Hamer, M.D., Nathan K. Jansen DO., Xiaotang Jing, BSN., Jael Kagai, B.S., Kamila Kourbanova, B.S., Michael A. Koren, M.D., Monica L. Martin, DVM., Kathryn McGuckin Wuertz, Ph.D., Jason A. Regules, M.D., Aaron D. Sanborn, BSN., David Wallace, B.S., Lei Zhu, BSN., Gregory D. Gromowski, Ph.D.

Henry M. Jackson Foundation for the Advancement of Military Medicine

Courtney Corbitt, B.S., Janice M. Darden, MS., Vincent Dussupt, Ph.D., Emily S. Golub, B.S., Jarrett A. Headley, B.S., Umair M. Jarral, M.D., Jocelyn King, BS., Shelly J. Krebs, Ph.D., Jenny Lay, MPH., Regina Lilly, M.D., Jennifer Lynch, B.S., Elizabeth J. Martinez, B.S., Sandra V. Mayer, Ph.D., Samantha McGeehon, MSc., Hyunna Lee, B.S., Steven Schech, B.S., Mekdi Tadesse, MBA, Paul V. Thomas, Ph.D., Yahel Romem, B.S., Erifile Zografos

Vaccine Research Center, National Institute of Allergy and Infectious Disease

Bob C. Lin, B.S., Sandeep R. Narpala, M.S., Lingshu Wang, Ph.D., Nicole A. Doria-Rose, Ph.D., Robin E. Carroll, B.S.

Duke Human Vaccine Institute, Duke University School of Medicine

Amanda Eaton, MBA.

Office of Regulated Activities (ORA) within the US Army Medical Research and Development Com

Emily D. Badraslioglu, M.S., Jason M. Koontz, Ph.D., Ugo E. Nwaeze M.D.

The EMMES Company

Peter Dawson, Ph.D. Alexander J. Noll, Ph.D., Christine M. Orndahl, Ph.D., Amy Bray, MA.

Texas Biomedical Research Institute

Ricardo Carrion Jr., Ph.D., Jean Patterson, Ph.D., Viraj Kulkarni, Ph.D., Cory Hallam, Ph.D., Olga Gonzalez, DMV, Michal Gazi, Ph.D.

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Supplementary Materials

Data Availability Statement

The Henry M Jackson Foundation for the Advancement of Military Medicine and the US Department of the Army are committed to safeguarding the privacy of research participants.

De-identified participant level data and accompanying research resources are available upon request. Distribution of data will require compliance with all applicable regulatory and ethical processes, including establishment and approval of an appropriate datasharing agreement. The research protocol, informed consent documents, and instructions for submitting data requests are available online.