Safety and Immunogenicity of a First-in-Human Mosquito Saliva Peptide Vaccine: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Safety and Immunogenicity of a First-in-Human Mosquito Saliva Peptide Vaccine (NCT03055000), a randomized phase 1 study. The primary outcome is AEs Grade 3 or Higher.

2. Clinical Question

3. Trial Design

This was a randomized, double-blind, placebo-controlled, Phase 1 study with a parallel-group model and quadruple masking recorded in the registry. The study is titled as a first-in-human evaluation of AGS-v in healthy volunteers. Its stated focus was safety and immunogenicity, meaning the safety profile and the immune response following vaccination. Enrollment was 49, and the study status is completed. The recorded start date is 2017-02-15 and the primary completion date is 2018-12-28.

Participants were assigned to receive unadjuvanted AGS-v, AGS-v with adjuvant, or placebo. Each arm description specifies two administrations, on Day 0 and Day 21. The registry summary describes monitoring after vaccination, follow-up visits, blood and urine testing, and a later mosquito-feeding visit. It also describes symptom diaries after vaccination. These planned activities provide context for the safety and immune measurements, but the registry record does not report the full visit schedule as an analysis plan or identify which specific visits contributed to every posted outcome.

The primary endpoint timeframe is 1 year after vaccination, with the endpoint described as grade 3 or higher adverse events within 1 year after 2 vaccinations 21 days apart. The listed primary population is all subjects who received vaccination. The record posts results for three arms, but it does not report an allocation ratio, the number randomized to each arm before exclusions, or a detailed account of missing observations and analysis-set construction. Arm-specific counts attached to individual outcomes can differ, so they should be interpreted as the denominators for those posted results rather than treated as a single universal analysis population.

Although randomization and masking can reduce some sources of bias, those design features do not substitute for a reported statistical analysis plan. The registry record does not report the randomization method, masking procedures, or prespecified inferential comparisons. No reported analyses are listed. The posted results are therefore best read as registry-reported arm summaries and exploratory outcome information, not as a complete account of the trial's planned statistical tests.

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

Analysis population for the primary outcome, as defined in the registry: All subjects who received vaccination

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.

6. Primary Endpoint

The registry lists the primary outcome as AEs Grade 3 or Higher, measured over 1 year after vaccination (study duration).

The primary endpoint is the mean number of adverse events graded 3 or higher, identified within 1 year after the two vaccinations. Grade 3 or higher describes the event-severity threshold chosen for this endpoint; the registry record does not provide further grading definitions in the result entry. A mean event count summarizes the average number of qualifying events per person in the stated population. It is not the same quantity as the proportion of participants who experienced at least one event: a participant may contribute more than one event to a count, whereas a participant-level proportion classifies each person according to whether an event occurred.

Safety is an important focus in a first-in-human Phase 1 study. Reporting more severe events over a stated follow-up period can describe the observed safety experience while participants receive and are followed after vaccination. However, the endpoint alone does not establish whether an event was caused by vaccination, nor does a group mean reveal the range or timing of individual experiences. The registry record does not report event-level details or a formal comparison for this primary outcome.

The posted arm summaries are means with 95% confidence intervals. A confidence interval conveys uncertainty around an estimated mean under the method used to construct it; it is not a range containing every participant's event count. Because this endpoint is presented as an arm-level mean and not as a reported contrast, the result supports descriptive reading of each arm. It does not by itself supply a precise estimate of how the vaccine compares with placebo.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry reports arm-level means and 95% confidence intervals for the primary endpoint. A mean is the arithmetic average of the measured event counts in the stated analysis population. It summarizes the center of the data, but can conceal differences between participants and does not reveal whether events were concentrated in a few people or distributed across the group. The registry record does not report a distribution of individual counts, a median, or the statistical method used to calculate these confidence intervals.

What does a confidence interval describe?

A confidence interval expresses uncertainty around an estimate. In general, narrower intervals indicate greater precision and wider intervals indicate less precision, conditional on the method's assumptions. A 95% confidence interval is not a guarantee that the true value lies within the displayed limits, and it does not describe the spread of individual observations. For the primary endpoint, the interval is attached to each arm's mean, not to a contrast between arms. A formal comparison would ordinarily require an estimated difference or another defined contrast with its own uncertainty measure; the registry record does not report such a primary comparison.

The secondary cytokine outcomes are continuous measurements reported as means with standard deviations. The standard deviation describes how dispersed individual measurements are around the mean. It is not the standard error, which concerns the precision of an estimated mean, and it is not a confidence interval. Greater variability can make an estimate less precise, particularly when the outcome analysis includes relatively few observations. This is a general statistical principle; it does not establish why a particular cytokine value varied in this study.

How should the recalculated comparisons be read?

For selected secondary outcomes, the posted contrast is a recalculated, unadjusted mean difference between an active arm and placebo. The calculation uses the arm-level summary statistics posted in the registry. It is not identified as an analysis reported by the investigators, and no reported analyses are listed. The contrast's confidence interval indicates uncertainty around that difference under the recalculation; an interval spanning zero is compatible with values on either side of no difference. This does not prove that the groups are identical. It indicates that the posted summaries do not provide a precise distinction from zero at the interval level.

The associated p-values are unadjusted. A p-value measures how incompatible the data are with a specified null model under the assumptions of the analysis; it is not the probability that the null hypothesis is true, nor a measure of clinical importance. The registry record does not report the investigators' model, test, or prespecified threshold for the secondary contrasts. The recalculated values therefore provide a limited descriptive comparison, not a replacement for a full trial analysis. Because several outcomes and arm comparisons are posted, interpreting any one unadjusted p-value without the wider testing context risks overstating chance patterns.

What do the planning illustrations mean?

The planning illustrations use the observed contrast as a starting point and show participant counts per arm for 80% power and 90% power under stated assumptions: a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. Rows describe planning for 100%, 75%, or 50% of the observed effect. These are hypothetical design illustrations, not observed results and not evidence that the completed trial had a particular power. Their values depend on the observed effect, which may be unstable in a small study. The registry record does not report that these assumptions were used to design the trial, or that the sample-size illustrations reflect the trial's own design.

More generally, a planning calculation asks how much information a future study might need to detect a chosen effect under assumed conditions. It does not correct limitations in the existing data, and it should not be interpreted as a recommendation for a particular study. If the observed effect is noisy, calculations based on it can be especially uncertain. The sample-size assumptions also specify equal allocation for the two-arm illustrations, while this trial has three arms; the planning exercise is therefore not a reconstruction of the original design.

Why does outcome type matter?

Event counts and continuous cytokine measurements have different data structures. A count may be skewed or contain many low values, and its variability may not follow the assumptions of a simple normal model. Continuous measurements may also be skewed or have unequal variance across groups. In general, over-dispersion occurs when count data vary more than a chosen model expects; accounting for it can affect uncertainty estimates. The registry record does not describe a count model, a transformation, or other distributional checks for the primary endpoint. The posted means and intervals can still be read descriptively, but the missing method details restrict assessment of how well the interval construction reflects the data.

All interpretation should keep the distinction between descriptive summaries, recalculated contrasts, and investigator-reported analyses in view. The record contains arm-level outcome values and selected recalculations, but no reported analyses. It does not report adjustment for baseline values, covariates, repeated measurements, or multiplicity. Those methods should not be assumed. The results are most defensible as a description of what was posted, with inferential conclusions kept cautious where the analysis procedure is not documented.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists multiple secondary outcomes, including cytokine levels and the number of adults developed from 100 eggs. The record does not report a multiplicity adjustment, a prespecified order for testing outcomes, or a distinction between confirmatory and exploratory secondary hypotheses. When many outcomes are examined, the chance of at least one apparently notable result can rise even if the underlying effects are absent. This is a general statistical concern, not a claim that a particular posted finding is false. It is why unadjusted secondary p-values should be interpreted cautiously and in the context of the full set of outcomes.

The registry record does not report a statistical analysis plan, interim analyses, a sample-size justification, or details of any outcome-specific analysis populations beyond the primary population description. It also does not report how missing data were handled, whether any participants were excluded from particular outcome analyses, or whether the analysis followed randomized assignment or vaccination received for each endpoint. The stated primary population is all subjects who received vaccination, while the posted arm denominators vary by outcome. These differences make it important not to assume one common set of participants or one uniform missing-data rule across the results.

Without a reported missing-data approach, it is not possible to judge whether missing measurements could have affected an arm summary or contrast. In general, results may be sensitive to why measurements are absent; methods that rely on different assumptions can produce different estimates. The registry record does not report reasons for missingness or sensitivity analyses. Nor does it report details about the handling of repeated measurements, if applicable to the underlying data. These are limitations in assessing robustness, not grounds to impute a particular result.

The record lists no reported analyses. Therefore, the posted summaries do not establish which tests were prespecified, how the investigators intended to control false-positive findings, or whether the displayed comparisons were part of the original analysis plan. The recalculated unadjusted contrasts can help orient a reader to the arm summaries, but they cannot fill those documentation gaps. Confirmatory interpretation would require a clearly described analysis strategy and complete outcome reporting.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent non-serious adverse event terms

The registry's separate safety summary reports zero serious adverse events affecting participants in each arm, with zero deaths recorded in each arm. It also reports other adverse events affecting 16 in the AGS-v group, 17 in the AGS-v With Adjuvant group, and 15 in the Placebo group. These are event-group counts, not the primary endpoint's mean count of grade 3 or higher adverse events. The categories and summaries should not be substituted for one another.

No serious events listed in these groups is a descriptive finding for this study, not proof that serious events are impossible or that the arms have equivalent safety. A small Phase 1 study can describe events observed during its follow-up but has limited ability to characterize uncommon harms. The registry record does not list top serious-event terms, provide individual event narratives, or report a comparative statistical analysis of these safety counts. It also does not establish causality for other adverse events. Interpretation should remain limited to the posted counts and their stated populations.

12. What the Result Does, and Does Not, Mean

The results describe what was recorded in a randomized Phase 1 study of AGS-v, with and without adjuvant, compared with placebo in healthy volunteers. The primary outcome is an arm-level mean count of grade 3 or higher adverse events over the stated follow-up. The posted values and confidence intervals offer a descriptive account of that endpoint, while the separate safety summary reports serious and other adverse events using participant counts.

These entries do not establish whether AGS-v prevents mosquito-borne disease. The study's stated purpose was to assess safety and immune response, and the listed primary endpoint is not a clinical disease outcome. The registry summary describes a possible broader rationale for targeting mosquito saliva proteins, but a rationale is not evidence of clinical benefit. The posted results also do not establish that observed adverse events were caused by vaccination or that any arm is safer than another.

The secondary cytokine outcomes provide immune measurements, but their recalculated comparisons are unadjusted and are not reported investigator analyses. They should not be treated as confirmatory evidence. The absence of a reported primary comparison, multiplicity plan, and missing-data approach limits the strength of inferential conclusions. Likewise, confidence intervals that overlap or contrasts whose intervals cross zero do not demonstrate equivalence; they indicate uncertainty in the available estimates.

In general, a small early-phase study can supply useful descriptive information and help identify questions for further research, but precision and generalizability depend on the data and analysis. The registry record concerns healthy adults in the stated age range and does not provide evidence for other populations. The findings should therefore be understood as registry-reported safety and immunogenicity information from this study, not as a definitive assessment of clinical effectiveness or a basis for individual medical decisions.

13. Why This Trial Matters Statistically

This trial is statistically notable because it places several types of evidence side by side: a mean count for a safety endpoint, participant counts for serious and other adverse events, and continuous cytokine measurements. Those summaries answer different questions. Separating them prevents the common mistake of treating an average event count as a risk percentage, or of using an immune marker as a substitute for a clinical outcome.

The posted primary results also illustrate the difference between an estimate and its precision. Arm means can look distinct while their confidence intervals remain broad and overlapping. Without a reported comparison, the mean values alone cannot establish a between-group effect. The secondary comparisons further illustrate why unadjusted analyses in a collection of outcomes should be regarded as exploratory, especially when no analysis plan or multiplicity strategy is reported.

Planning illustrations can help show how a future study's required size depends on the effect chosen for detection and on assumptions about design and analysis. They do not describe the power of this completed study, and they do not recover a missing sample-size justification. Treating planning estimates as conditional scenarios, rather than as evidence about observed performance, is essential to a sound reading.

Finally, the registry record makes visible an important reporting issue: design labels and outcome values do not replace details of the statistical plan. Information about analysis populations, missing data, prespecified comparisons, and multiplicity is needed to judge how robust an inferential claim would be. This study is useful for learning how early-phase registry findings can be described carefully without overstating what they establish.

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 registry record leaves several trial-specific uncertainties. It does not report the statistical analysis plan, the sample-size justification, randomization procedures, or the detailed masking procedures. Although the study is described as randomized and quadruple-masked, those labels alone do not show how allocation and masking were implemented or maintained.

The primary endpoint is a mean count, but the record does not explain the distribution of individual event counts, the interval calculation method, or any model used. It gives no event-level breakdown for the primary outcome. The separate adverse-event entry does not list serious-event terms, and the registry record does not report a detailed account of event timing, severity grading, or attribution. This limits assessment of the clinical context behind the summaries.

Outcome denominators vary, and the record does not explain the reasons for those differences or how missing observations were handled. It does not identify whether analyses were based on randomized assignment, vaccination received, or another rule for each endpoint. For the secondary outcomes, no investigator-reported analyses are listed, and the recalculated contrasts are unadjusted. The record also does not report a strategy for multiplicity or identify which secondary outcomes were intended to be confirmatory.

Finally, this was a Phase 1 study in healthy volunteers, and the posted results do not include a clinical disease-prevention endpoint. The summaries therefore have limited scope for conclusions about other populations or clinical outcomes. The study's status as completed does not resolve the uncertainty created by missing analysis details. These limitations do not negate the descriptive results; they define how cautiously those results should be interpreted.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Safety and Immunogenicity of a First-in-Human Mosquito Saliva Peptide Vaccine — NCT03055000.
• Registry record last updated 2020-08-11; status last verified 2018-12.
• Results first posted 2020-08-03.
• 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.

18. Record Summary

NCT03055000 is a completed randomized, double-blind, placebo-controlled, Phase 1 study of AGS-v in healthy volunteers. It compared unadjuvanted AGS-v, AGS-v with adjuvant, and placebo, with the arm descriptions specifying vaccinations on Day 0 and Day 21. The primary endpoint was the mean number of grade 3 or higher adverse events within 1 year after vaccination, among all subjects who received vaccination.

The registry posts arm-level primary summaries, separate adverse-event counts, and selected secondary outcomes, including cytokine measurements. It does not list investigator-reported analyses or provide a primary between-arm comparison. Recalculated secondary contrasts are unadjusted and exploratory. Missing-data handling, multiplicity procedures, and the statistical analysis plan are not reported in the registry record. The findings are therefore most appropriately read as descriptive safety and immunogenicity information, with substantial limits on confirmatory interpretation.