This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Efficacy of Na-GST-1/Alhydrogel Hookworm Vaccine Assessed by Controlled Challenge Infection (NCT03172975), a randomized phase 2 study. The primary outcome is Detectable Hookworm Infection.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT03172975 |
| Phase | Phase 2 |
| Condition | Hookworm Infections |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Quadruple |
| Enrollment | 39 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Baylor College of Medicine |
| Results posted | Yes |
2. Clinical Question
Population
Healthy, hookworm-naïve adults enrolled in a Phase 2 study. The registry record reports enrollment of 39 participants and states that the number analyzed at each weekly visit varies because participants missed visits.
Intervention
Na-GST-1/Alhydrogel, either without an added agonist or co-administered with CPG 10104 or GLA-AF. The listed regimens were administered intramuscularly on study days 0, 56 and 112, followed by controlled infection with 50 infectious Necator americanus larvae on study day 140.
Comparator
Sterile saline placebo administered intramuscularly on study days 0, 56 and 112, also followed by controlled infection with 50 infectious Necator americanus larvae on study day 140. Albendazole is listed as an intervention, but the registry record does not describe it as a randomized comparison group in the arm details.
Primary question
After controlled challenge infection, how many participants had detectable hookworm eggs in fecal samples at any of the specified post-challenge time points, as determined by microscopy using the qualified saline flotation technique? The registry record does not report the group results or an estimated comparison between formulations and placebo.
3. Trial Design
This was a randomized, quadruple-masked, parallel-group Phase 2 study. The registry record lists enrollment of 39 and describes the study as completed. The recorded start date is 2018-03-01, and the primary completion date is 2024-12-31. The study evaluated safety, efficacy and immunogenicity of Na-GST-1 formulations in a controlled human hookworm infection model in healthy, hookworm-naïve adults.
The arm descriptions cover Na-GST-1/Alhydrogel alone, Na-GST-1/Alhydrogel with CPG 10104, Na-GST-1/Alhydrogel with GLA-AF, and saline placebo. The active formulations were given intramuscularly in the deltoid on study days 0, 56 and 112. The descriptions then specify challenge with 50 infectious Necator americanus larvae on study day 140. The listed doses were 100 µg Na-GST-1/Alhydrogel, 500 µg CPG 10104 when included, and 5 µg GLA-AF when included.
Albendazole and Necator americanus larval inoculum are also listed among the interventions. The arm descriptions identify the placebo and vaccine regimens but do not explain an albendazole treatment schedule or its role in the group comparisons. The allocation ratio, randomization procedure, masking procedures, and details of any stratification are not reported in the registry record. These omissions prevent a fuller account of how participants were assigned and how masking was maintained.
4. Participant Flow and Accounting
The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.
Overall Study
| Stage | Na-GST-1/Alhydrogel | Na-GST-1/Alhydrogel + CPG 10104 | Na-GST-1/Alhydrogel + GLA-AF | Saline Placebo |
|---|---|---|---|---|
| STARTED | 10 | 9 | 10 | 10 |
| COMPLETED | 9 | 5 | 10 | 8 |
| NOT COMPLETED | 1 | 4 | 0 | 2 |
Analysis population for the primary outcome, as defined in the registry: The number of participants analyzed each week varies due to participants missing that visit.
5. Baseline Characteristics
The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.
| Characteristic | Unit | Na-GST-1/Alhydrogel | Na-GST-1/Alhydrogel + CPG 10104 | Na-GST-1/Alhydrogel + GLA-AF | Saline Placebo | Total |
|---|---|---|---|---|---|---|
| Participants analysed | 10 | 9 | 10 | 10 | 39 | |
| Age, Continuous | Years | 26.1 (SD 4.6) | 30.4 (SD 8.2) | 24.7 (SD 3.3) | 26.1 (SD 3.45) | 26.7 (SD 5.4) |
| Age, Customized: Age, Continuous | Years | 25.5 (19.0 to 34.0) | 29.0 (21.0 to 44.0) | 23.5 (21.0 to 30.0) | 25.5 (22.0 to 31.0) | 26.0 (19.0 to 44.0) |
| Sex: Female, Male: Female | Participants | 4 | 5 | 6 | 7 | 22 |
| Sex: Female, Male: Male | Participants | 6 | 4 | 4 | 3 | 17 |
| Race/Ethnicity, Customized: Race – American Indian or Alaska Native | Participants | 0 | 1 | 0 | 0 | 1 |
| Race/Ethnicity, Customized: Race – Asian | Participants | 0 | 0 | 4 | 1 | 5 |
| Race/Ethnicity, Customized: Race – Black or African American | Participants | 1 | 1 | 0 | 1 | 3 |
| Race/Ethnicity, Customized: Race – Other | Participants | 1 | 2 | 0 | 2 | 5 |
| Race/Ethnicity, Customized: Race – White | Participants | 8 | 5 | 6 | 6 | 25 |
| Race/Ethnicity, Customized: Ethnicity – Hispanic or Latino | Participants | 1 | 3 | 1 | 2 | 7 |
| Race/Ethnicity, Customized: Ethnicity – Not Hispanic or Latino | Participants | 9 | 6 | 9 | 8 | 32 |
6. Primary Endpoint
The registry lists the primary outcome as Detectable Hookworm Infection, measured over On Study Days 175, 182, 189, 203, 217, 231, 245, 259, 273, and 280..
| Element | Registry entry |
|---|---|
| Result type | Count Of Participants |
| Measure of spread | not applicable |
| Unit | Participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint is detectable hookworm infection, expressed as the number of participants with detectable hookworm eggs in fecal samples at any time point. Microscopy using the qualified saline flotation technique was used to determine egg detection. The registry lists post-challenge assessments on study days 175, 182, 189, 203, 217, 231, 245, 259, 273 and 280.
This endpoint captures whether egg detection occurred during the specified observation period rather than describing the number of eggs in each sample. In general, a participant-level indicator of detectable infection can provide an interpretable summary of whether infection was detected, while fecal egg counts address the amount of egg shedding. The registry also lists fecal egg counts and anti-Na-GST-1 IgG antibody response as secondary outcomes.
The registry record says that the number of participants analyzed each week varies because of missed visits. It does not report the endpoint results, the number with detectable eggs in each group, or how observations from missed visits were handled in deriving any participant-level outcome.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies a clinically specific primary outcome: detection of hookworm eggs in fecal samples after controlled challenge. It also specifies the microscopy method and the post-challenge assessment days. However, it does not report numerical results for this outcome. Group-level counts or proportions, a contrast between vaccine formulations and placebo, and measures of uncertainty are not reported in the registry record. The record lists 0 analyses.
As a result, the registry information does not establish the direction or size of any difference in detectable infection between groups. It also does not support a conclusion about whether any formulation changed the probability of egg detection. Absence of a posted estimate is not evidence of equal outcomes, and it should not be interpreted as evidence that a difference was absent. The registry record simply does not provide the numerical primary-outcome comparison needed to judge that question.
The endpoint definition combines detections across the specified visits by referring to detectable eggs at any time point. Separately, the registry notes that the number analyzed varies by week because of missed visits. Those details matter for interpretation: the pattern of visit attendance can affect which observations contribute, and the record does not explain how missing visits were incorporated into the overall endpoint. It also does not report whether analyses were conducted separately by visit, as an overall participant-level measure, or by another approach.
In general, an effect estimate describes the size and direction of a comparison, while a confidence interval conveys the precision of that estimate under the analysis assumptions. Neither is reported for the primary outcome in the registry record. No p-value or statistical test result is reported either. Without those results and the analysis details, statistical uncertainty and the evidence for between-group differences cannot be assessed from the registry information.
The study includes safety and immunogenicity aims, and the registry lists fecal egg counts and anti-Na-GST-1 IgG antibody response as secondary outcomes. Their numerical results and analysis details are not reported in the registry record. The serious adverse-event counts are available as descriptive safety information, but they do not substitute for the missing efficacy results.
9. Statistical Methods Explained
What does the primary endpoint count?
The registry describes the primary outcome as a count of participants with detectable hookworm eggs, with detection assessed in fecal samples by microscopy. The endpoint description defines the event using detection at any time point during the specified post-challenge assessments. A participant-level event indicator is a binary outcome: each participant either meets the stated detection definition or does not. Reporting a count of participants is not, by itself, a complete comparison. To interpret group differences, readers also need the relevant group denominators and an estimate comparing the groups. Those numerical efficacy results are not reported in the registry record.
In general, binary outcomes are often summarized as group proportions and compared using an effect measure suited to the study design and analysis plan. The choice of effect measure and method should be prespecified and interpreted alongside uncertainty. The statistical method selected for this trial's primary outcome is not reported in the registry record, so no particular test or model can be attributed to the study.
Why do repeated assessment times matter?
The endpoint covers multiple post-challenge assessment days, and the registry separately notes that the number analyzed varies each week because participants missed visits. Repeated observations on the same participant are not generally independent: a person's status at one visit may be related to status at another. In general, an analysis that treats repeated observations as independent can misrepresent uncertainty if that dependence is ignored. A participant-level summary such as detection at any time point, a visit-specific analysis, or a repeated-measures model would answer somewhat different statistical questions. The registry record does not report which approach was used for the analysis, beyond its description of the endpoint.
Missing visits also require an explicit analytic approach. In general, available-visit summaries describe the observations recorded at each visit, while methods that account for missingness rely on additional assumptions. Different assumptions can lead to different interpretations if missingness is related to outcome status or treatment group. The registry record acknowledges variable weekly analysis counts but does not report the reasons for missed visits, a missing-data method, or sensitivity analyses.
How should uncertainty and significance be read?
In general, a confidence interval describes a range of values compatible with the data and analysis assumptions; a wider interval indicates less precision than a narrower interval. A p-value summarizes how unusual data would be under a specified null hypothesis and model, but it does not measure the size or clinical importance of an effect. Neither confidence intervals nor p-values for the primary endpoint are reported in the registry record. No estimate of the primary comparison is available to interpret for magnitude or precision.
The record includes planning assumptions for an illustrative sample-size calculation: a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect defined as a stated fraction of the observed effect. These are described as planning illustrations rather than the trial's own design. The record does not report the actual illustration values or a sample-size justification used to design this trial. Such calculations are not observed power and do not indicate what the trial found.
What does over-dispersion mean?
In general, over-dispersion arises when count data vary more than a statistical model expects. If a count outcome is over-dispersed and a model fails to account for it, estimated uncertainty can be too small. This can be relevant to analyses of count outcomes such as fecal egg counts, depending on their distribution and the model used. The registry record lists fecal egg counts as a secondary outcome but does not report their numerical results, distribution, or analysis method. There is no basis for concluding that a particular count model or over-dispersion adjustment was used in this trial.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 10 outcome measures and identifies fecal egg counts and anti-Na-GST-1 IgG antibody response as secondary outcomes. The primary endpoint also refers to detection across multiple post-challenge assessment days. Considering multiple outcomes, visits, or comparisons can increase the chance of finding an apparently notable result by chance if each is tested separately. In general, a prespecified testing hierarchy or multiplicity adjustment can address this issue, but the registry record does not report a multiplicity strategy, a hierarchy among outcomes, or an analysis plan for multiple comparisons.
The record lists 0 analyses and does not provide numerical results or statistical tests for the primary or secondary outcomes. It is therefore not possible to determine which outcomes were analyzed, whether all planned analyses are reported, or whether any adjustment for multiple testing was applied. The endpoint description and list of outcomes do not establish that a particular test was performed.
Missingness is relevant because the registry says the number analyzed at each weekly visit varies due to missed visits. It does not report the amount or pattern of missing data by group, how missing visits were handled, or whether sensitivity analyses were conducted. The analysis population is also not reported in the registry record. In particular, the record does not specify whether the primary analysis followed an intention-to-treat, per-protocol, or another population definition. These details limit assessment of the potential effect of missing data and the population to which any eventual estimate would apply.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Na-GST-1/Alhydrogel | 0 | 10 | 0.0% |
| Na-GST-1/Alhydrogel + CPG 10104 | 1 | 9 | 11.1% |
| Na-GST-1/Alhydrogel + GLA-AF | 0 | 10 | 0.0% |
| Saline Placebo | 0 | 10 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Na-GST-1/Alhydrogel | 0 of 10 |
| Na-GST-1/Alhydrogel + CPG 10104 | 0 of 9 |
| Na-GST-1/Alhydrogel + GLA-AF | 0 of 10 |
| Saline Placebo | 0 of 10 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Na-GST-1/Alhydrogel | 10 of 10 |
| Na-GST-1/Alhydrogel + CPG 10104 | 9 of 9 |
| Na-GST-1/Alhydrogel + GLA-AF | 10 of 10 |
| Saline Placebo | 10 of 10 |
Most frequent serious adverse event terms
| Event term | Organ system | Na-GST-1/Alhydrogel | Na-GST-1/Alhydrogel + CPG 10104 | Na-GST-1/Alhydrogel + GLA-AF | Saline Placebo |
|---|---|---|---|---|---|
| Hospitalization | General disorders | 0 of 10 | 1 of 9 | 0 of 10 | 0 of 10 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Na-GST-1/Alhydrogel | Na-GST-1/Alhydrogel + CPG 10104 | Na-GST-1/Alhydrogel + GLA-AF | Saline Placebo |
|---|---|---|---|---|---|
| Injection Site Tenderness | General disorders | 10 of 10 | 8 of 9 | 10 of 10 | 6 of 10 |
| Injection Site Pain | General disorders | 10 of 10 | 7 of 9 | 8 of 10 | 6 of 10 |
| Eosinophil Count Increased | Investigations | 8 of 9 | 2 of 5 | 10 of 10 | 8 of 9 |
| Headache | Nervous system disorders | 4 of 10 | 8 of 9 | 2 of 10 | 8 of 10 |
| Application Site Discolouration | General disorders | 8 of 9 | 0 of 5 | 7 of 10 | 6 of 9 |
| Application Site Pruritus | General disorders | 5 of 9 | 5 of 5 | 5 of 10 | 4 of 9 |
| Abdominal Bloating | Gastrointestinal disorders | 5 of 9 | 3 of 5 | 6 of 10 | 5 of 9 |
| Nausea | Gastrointestinal disorders | 4 of 9 | 3 of 5 | 6 of 10 | 6 of 9 |
| Flatulence | Gastrointestinal disorders | 5 of 9 | 1 of 5 | 7 of 10 | 6 of 9 |
| Abdominal Pain | Gastrointestinal disorders | 4 of 9 | 3 of 5 | 6 of 10 | 5 of 9 |
Serious events with the highest arm-level rate: hospitalization (11.1%).
The registry reports serious adverse-event counts by group. Serious adverse events were recorded for 0 of 10 at risk in the Na-GST-1/Alhydrogel group, 1 of 9 at risk in the Na-GST-1/Alhydrogel + CPG 10104 group, 0 of 10 at risk in the Na-GST-1/Alhydrogel + GLA-AF group, and 0 of 10 at risk in the saline placebo group. Deaths were recorded as 0 in each group.
Hospitalization is listed as a top serious adverse-event term at 11.1%. The registry record does not specify in this summary which group the term belongs to or the denominator used for that percentage. It should therefore be read as a registry-reported term and percentage, not as a group-specific comparison.
For other adverse events, the registry records 10 affected among 10 at risk in each group. These descriptive counts do not by themselves show whether events differed in type, timing, severity, or relationship to study treatment. The registry information presented does not include those details or comparative statistical analyses. Counts should be interpreted in their recorded group context and not treated as proof of either safety or harm.
12. What the Result Does, and Does Not, Mean
The registry record documents a randomized, quadruple-masked, parallel-group controlled challenge study evaluating Na-GST-1/Alhydrogel formulations in healthy, hookworm-naïve adults. It defines detectable hookworm eggs in fecal samples as the primary outcome and identifies the microscopy method and assessment days. Those design and measurement details clarify what the study intended to assess.
They do not establish the outcome. Numerical results for detectable infection, group comparisons, confidence intervals, and p-values are not reported in the registry record. Consequently, the posted information cannot show whether outcomes differed between a vaccine formulation and saline placebo, nor can it quantify the size or precision of any difference. Missing numerical results should not be read as proof of no effect or as proof of an effect.
The safety summary records serious adverse events and deaths by group and lists hospitalization as a top serious term. These are descriptive registry data. They do not provide a complete account of event characteristics or establish a causal relationship with a study intervention. The secondary outcomes are identified, but their numerical findings are not reported in the registry record.
In general, a controlled challenge model gives investigators a defined exposure and an outcome measured after that exposure. Results from such a study still need to be interpreted in light of the participants studied, the analysis population, missing observations, and the statistical methods used. Those analysis details are not reported in the registry record. The information available supports a description of the study question and design, but not a conclusion about efficacy or comparative safety.
13. Why This Trial Matters Statistically
This trial is statistically notable for pairing a defined controlled challenge with an endpoint based on detecting hookworm eggs in fecal samples. The registry specifies the microscopy approach and a series of post-challenge assessment days. That makes the outcome concept understandable, while also raising analytic questions about repeated observations and missed visits.
The record says weekly analysis counts vary because participants missed visits, but does not explain the missing-data approach or how the repeated assessment times contribute to the endpoint. In general, these choices affect the interpretation of an estimate and its uncertainty. A transparent account of the analysis population, endpoint derivation, missing-data handling, and statistical model would help readers assess whether the reported comparison matches the research question.
The study also lists secondary outcomes for fecal egg counts and antibody response. These outcomes represent different kinds of measurements and may require different statistical methods. The registry record does not report their results or analysis plans, and it lists 0 analyses. Readers therefore cannot evaluate consistency across outcomes or account for potential multiplicity from the registry information.
The main statistical lesson is the distinction between a clearly defined design and an evaluable result. Randomization, masking, and a specified outcome describe how a trial was structured, but effect estimates and measures of uncertainty are needed to assess what the trial found. In this record, those primary efficacy results are not reported.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The central limitation for statistical interpretation is that the registry record does not report numerical primary-outcome results or a comparison between groups. It also does not report confidence intervals, p-values, or the statistical method used for the primary outcome. Efficacy and immunogenicity conclusions therefore cannot be drawn from the posted results described in the record.
The endpoint spans multiple post-challenge visits, and the number analyzed varies by week because of missed visits. The registry does not explain how those visits were combined, how missing observations were handled, or whether the analysis used all randomized participants or a defined subset. The allocation ratio and randomization procedures are not reported either. These omissions limit evaluation of the analysis and its susceptibility to bias.
Although the study is described as randomized and quadruple-masked, the registry record does not describe the masking procedures, an analysis plan, sample-size justification, interim analyses, or a multiplicity strategy. The sample-size assumptions are explicitly planning illustrations rather than the trial's own design; no illustration value or trial-specific justification is reported. The roles and schedules for listed albendazole are not explained in the arm descriptions.
The registry includes descriptive serious adverse-event counts, but does not provide detailed event-level context or a group-specific interpretation of the hospitalization percentage. These limitations concern what can be established from the registry record; they do not imply that analyses or details were absent from other records.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Efficacy of Na-GST-1/Alhydrogel Hookworm Vaccine Assessed by Controlled Challenge Infection — NCT03172975.
- Registry record last updated 2026-03-12; status last verified 2026-02.
- Results first posted 2025-12-05.
- Data retrieved from ClinicalTrials.gov on 2026-11-09.
- Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.
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18. Record Summary
NCT03172975 is a completed randomized, quadruple-masked, parallel-group Phase 2 study sponsored by Baylor College of Medicine. It enrolled 39 healthy, hookworm-naïve adults and assessed Na-GST-1/Alhydrogel formulations in a controlled human hookworm infection model. The recorded start date is 2018-03-01 and the primary completion date is 2024-12-31.
The primary outcome is detectable hookworm eggs in fecal samples at any specified post-challenge assessment, determined by microscopy using the qualified saline flotation technique. The registry lists fecal egg counts and anti-Na-GST-1 IgG antibody response as secondary outcomes. It reports serious adverse-event counts by group, but numerical primary efficacy results, analysis methods, and measures of uncertainty are not reported in the registry record.