Vaccine Treatment for Ebola Virus in Healthy Adults (V920-001): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Vaccine Treatment for Ebola Virus in Healthy Adults (V920-001) (NCT02269423), a randomized phase 1 study. The primary outcome is Number of Participants With One or More Solicited Local Treatment-Emergent Adverse Events (TEAE).

2. Clinical Question

3. Trial Design

The registry record describes a Phase 1, randomized, single-center, placebo-controlled, dose-escalation study of the V920 Ebola virus vaccine candidate, also identified as BPSC-1001 and VSVΔG-ZEBOV. The study was completed. Its recorded start date is 2014-10-13, and its primary completion date is 2015-08-25. The total enrollment was 39.

The design is listed as randomized and parallel. Three cohorts received different vaccine doses, with a placebo injection in the opposite deltoid; the placebo cohort received placebo in both deltoids. All injections were described as 1-mL intramuscular injections on Day 0. The registry record lists 10 participants in each of the three vaccine cohorts and 9 in the placebo cohort for the primary endpoint.

The registry record’s official title describes the study as double-blind, while its masking field records triple masking. It does not report which specific roles were masked or explain the difference between those descriptions. The design also identifies the study as single-center, but the center’s name is not reported in the registry record.

The stated study purpose was to assess safety and immunogenicity across different vaccine doses in healthy adults. The primary outcome was a count of participants with at least one solicited local TEAE through 14 days postvaccination. Listed secondary outcomes include geometric mean titers of ZEBOV envelope glycoprotein-specific binding antibodies and ZEBOV-specific neutralizing antibodies, counts of participants with vaccine viremia or vaccine shedding/excretion in saliva or urine, and mean vector RNA copy number. Five secondary outcomes are posted in the record. The protocol’s allocation sequence, operational details of dose escalation, and sample-size justification are not reported in the registry record.

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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: All randomized participants who received study vaccination (V920 dose level or placebo).

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 Number of Participants With One or More Solicited Local Treatment-Emergent Adverse Events (TEAE), measured over Up to 14 days postvaccination.

The primary endpoint counts participants who had one or more solicited local treatment-emergent adverse events after injection, with assessment through 14 days postvaccination. The registry definition of a TEAE is an adverse event that starts or worsens on or after the date and time of study vaccination. The specified local signs and symptoms are pain, erythema (redness), and induration (swelling). A memory aid was used to record participant observations.

This endpoint is a participant-level count: a participant is counted if at least one of the specified events occurs. The count does not indicate how many total episodes occurred, how long symptoms lasted, or how severe they were. Those details are not reported for this endpoint in the registry record. The registry also defines an adverse event as an untoward medical occurrence that does not necessarily have a causal relationship with the study vaccine. Therefore, inclusion as a TEAE identifies timing relative to vaccination, not proof that vaccination caused the event.

In a Phase 1 study, a specified short-term safety outcome can describe the observed frequency of particular reactions in the enrolled cohorts. Here, the endpoint concerns local reactogenicity, rather than the systemic adverse-event profile or immune response. The counts alone do not establish how the groups differ statistically, and they do not describe events outside the stated observation window.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The posted primary outcome is binary at the participant level: each participant either had at least one qualifying solicited local TEAE during the observation period or did not. The registered result is expressed as a count of participants in each cohort. The listed cohort sizes provide the context for reading those counts, but no additional rate, risk difference, relative measure, or inferential statistic is reported for this endpoint.

What does a participant count represent?

A count of participants with an event is different from a count of all event episodes. If a participant experienced more than one specified local sign or symptom, the primary endpoint still counts that person once. The registry outcome title and description define the threshold as one or more solicited local TEAEs. The results do not separately report the number of participants with pain, redness, or swelling, nor do they give symptom-level severity or duration.

The outcome is also distinct from an adverse event judged to be caused by treatment. The registry defines a TEAE by its timing: the event starts or worsens on or after vaccination. Its general adverse-event definition says the event does not necessarily have a causal relationship with study vaccine. Thus, the endpoint is useful for describing observed events in the specified period, while causal interpretation requires more than temporal classification.

Why do the cohort sizes matter?

Counts are interpreted in relation to how many participants were observed in each cohort. The primary results record 10 participants in each vaccine cohort and 9 in the placebo cohort. These are small cohorts, so the observed counts describe only the participants enrolled and do not, on their own, give a precise estimate of event frequency in a broader population. General statistical context: estimates from small samples tend to be more uncertain than estimates from larger samples, although the amount of uncertainty depends on the outcome and method.

The study used randomized parallel cohorts, which means participants were assigned to one of the study groups rather than all participants receiving each group’s assigned intervention in sequence. Randomization can help balance factors between groups on average, but it does not guarantee that small groups are balanced on every characteristic. Baseline characteristics and details of the randomization procedure are not reported in the registry record.

What can an inferential comparison add?

A statistical comparison can quantify whether the observed group differences are compatible with a range of underlying differences, given a specified model and assumptions. A confidence interval is one way to express the precision of an estimate. A p-value is one way to summarize how data compare with a stated null hypothesis under a statistical model. Neither is reported for the primary endpoint in the registry record. Without a reported test or interval, the counts should not be described as establishing a statistically significant difference or equivalence.

The results are not presented as adjusted estimates. The statistical model, covariates, handling of repeated events, and any stratification are not reported in the registry record. Because the endpoint is a count of participants with at least one event, it does not require an interpretation of event counts as a rate over person-time; the registry does not report person-time for this endpoint.

How should the dose cohorts be read?

The three vaccine cohorts correspond to 3x10^6 pfu, 2x10^7 pfu, and 1x10^8 pfu. Dose escalation is part of the study title, but the operational rules used to move between dose cohorts are not reported in the registry record. The observed counts can be described in their assigned cohorts. They should not be treated as evidence of a dose-response relationship without a specified analysis and consideration of uncertainty. The registry record does not report a trend test or another formal dose-response analysis for this primary endpoint.

The placebo arrangement also matters when describing the intervention. Participants in a vaccine cohort received a vaccine injection in one deltoid and a placebo injection in the opposite deltoid, while the placebo cohort received placebo in both deltoids. The primary outcome is reported by cohort, not separately by injection site. The record does not explain how events were attributed to one side or the other, so the posted cohort counts cannot be interpreted as site-specific comparisons.

What is the role of planning calculations?

General statistical context: sample-size planning asks how many participants might be needed under stated assumptions to detect a specified effect with a chosen error rate and power. Such planning values are not observed outcomes and do not describe the probability that a treatment effect is true. The registry record does not report the trial’s sample-size justification or its own planned power calculation. Any planning illustration based on the observed effect is separate from the trial’s design rationale and should not be called observed power.

For this endpoint, no sample-size assumptions or target effect used by the study investigators are reported in the registry record. The reported cohort sizes describe enrollment and analysis counts; they do not reveal whether the study was designed to detect a particular difference in local TEAEs. The results are therefore most appropriately interpreted as descriptive counts from a small Phase 1 study, with the inferential limits noted above.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("3x10^6 Plaque-forming Units (Pfu) Vaccine Cohort", "2x10^7 Pfu Vaccine Cohort", "1x10^8 Pfu Vaccine Cohort", "Placebo Cohort")
n      <- c(10, 10, 10, 9)
events <- c(8, 8, 10, 3)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  3x10^6 Plaque-forming Units (Pfu) Vaccine Cohort  10  8  80.0  44.4  97.5  49.0  94.3  48.2  94.0
ARM  2x10^7 Pfu Vaccine Cohort  10  8  80.0  44.4  97.5  49.0  94.3  48.2  94.0
ARM  1x10^8 Pfu Vaccine Cohort  10  10  100.0  69.2  100.0  72.2  100.0  71.5  99.8
ARM  Placebo Cohort  9  3  33.3  7.5  70.1  12.1  64.6  12.2  65.2

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists 14 outcome measures, 12 analyses, and 5 posted secondary outcomes. These counts indicate that the study collected or planned to report several outcomes, but they do not establish how investigators prioritized them or handled the chance of false-positive results across multiple statistical tests. A multiplicity adjustment, testing hierarchy, or prespecified family of hypotheses is not reported in the registry record.

The primary endpoint population is described as all randomized participants who received study vaccination. The posted primary cohort sizes are 10 participants in each vaccine cohort and 9 in the placebo cohort. The record does not report the number screened, the number randomized but not vaccinated, exclusions from the endpoint analysis, or a flow of participants through follow-up. It also does not describe how missing endpoint observations were handled or whether any participants had incomplete observation during the period through 14 days postvaccination.

For the primary endpoint, the registry gives counts by cohort, but it does not report confidence intervals, p-values, adjusted estimates, or a formal comparison with placebo. The reason a particular analysis was not reported is not reported in the registry record. The record does not specify an intention-to-treat analysis, a per-protocol analysis, or a sensitivity analysis for missing data. These omissions limit assessment of how robust the posted results are to analysis choices and incomplete follow-up.

General statistical context: multiplicity matters most when several inferential claims are made from a collection of outcomes or comparisons. Missing-data methods matter when some participants lack outcome observations, because the handling approach can affect estimates. Without details on the planned analysis and completeness of observations, neither issue can be fully evaluated for this result.

12. 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 serious adverse event figures record 0 affected participants in each cohort: the three vaccine cohorts, each with 10 participants at risk, and the placebo cohort, with 9 participants at risk. The death count is also 0 in every cohort. These figures describe the posted serious-event and death counts for the study record; they do not establish that no event could occur outside the period or population captured by the record.

The registry separately records other adverse events affecting 10 participants in each vaccine cohort and 9 in the placebo cohort. These are not the same as the primary endpoint. The primary endpoint specifically counts participants with one or more solicited local TEAEs through 14 days postvaccination, whereas the safety summary’s “other adverse events” category is a broader recorded category. The registry record does not provide further detail in the registry record about the terms, severity, timing, or causal attribution of those other events.

A count of zero is an observed count, not proof that the underlying risk is zero. General statistical context: with small groups, an event that was not observed may still be possible in a broader population. The registry record does not report precision estimates for these safety counts or a formal comparison between cohorts. The counts should therefore be read as a description of events recorded among enrolled participants, not as a definitive estimate of rare-event risk.

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

The primary posted results describe the occurrence of specified local events in four cohorts. The recorded counts were 8 participants in the 3x10^6 pfu cohort, 8 in the 2x10^7 pfu cohort, 10 in the 1x10^8 pfu cohort, and 3 in the placebo cohort. The endpoint covers one or more solicited local TEAEs through 14 days postvaccination and includes pain, redness, and swelling. These counts provide a short-term, cohort-level description of the endpoint as defined in the registry.

They do not show how many individual symptoms occurred, how severe or persistent they were, or whether an event was caused by the vaccine. They also do not establish a statistical difference between any vaccine dose and placebo: no inferential comparison or uncertainty interval for the primary endpoint is reported in the registry record. In particular, the counts should not be used by themselves to claim that one dose is safer or less safe than another.

The trial’s stated aims included evaluating immune response, and its listed secondary outcomes include antibody titers and measures related to vaccine viremia and shedding or excretion. The primary result is not an immunogenicity result. The specific secondary-outcome results are not reported in the registry record, so no conclusion about antibody response or those virologic outcomes follows from the local-event counts.

The findings also do not establish protection against Ebola virus or answer questions about outcomes in people outside the healthy adult study population. The record describes a Phase 1 study with 39 participants distributed across four cohorts, and the primary endpoint covers a limited period after vaccination. General statistical context: early-phase studies can characterize observations in the enrolled groups, but broader inference depends on the population, follow-up, precision, and analysis. Those limits are especially relevant when interpreting small-group safety counts.

The balanced interpretation is therefore narrow: local TEAEs were recorded in the reported counts during the specified observation window, and the serious adverse event and death counts were zero in every cohort. The posted information does not provide the statistical comparisons or longer-term evidence needed to support stronger claims.

14. Why This Trial Matters Statistically

This trial illustrates the difference between describing events and estimating a comparative treatment effect. The registry provides participant counts for a clearly defined short-term local safety endpoint in three dose cohorts and a placebo cohort. Those counts are directly interpretable as observed events among enrolled participants, but they are not accompanied by reported confidence intervals or hypothesis tests for the primary endpoint.

The dose-cohort structure also highlights why design and analysis details matter. Different assigned vaccine doses can motivate questions about how outcomes vary with dose, but a sequence of observed counts is not itself a formal dose-response analysis. The registry record does not report a trend test, dose-selection rule, or prespecified comparisons. Without those details, statistical interpretation should remain descriptive.

The study also makes the distinction between event timing and event causation important. The registry defines TEAEs by whether an event starts or worsens after vaccination, while stating that an adverse event does not necessarily have a causal relationship with study vaccine. Reporting the endpoint using that definition supports consistent counting, but does not prove a treatment caused the events.

Finally, the small cohort sizes and lack of reported precision estimates demonstrate why event counts need context. The observed data can inform an account of what occurred among these participants, while uncertainty about broader event frequency remains. This is a useful statistical lesson for reading early-phase safety results: the definition, observation period, analysis population, cohort size, and inferential information all shape what can responsibly be concluded.

15. 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 primary endpoint is limited to solicited local symptoms and signs through 14 days postvaccination. It does not capture all possible adverse events, and the record does not report symptom severity, duration, or separate counts for pain, erythema, and induration. The endpoint is based on participant reports recorded with a memory aid, as described in the registry.

The study enrolled 39 participants across three vaccine cohorts and one placebo cohort. The posted cohort sizes are 10, 10, 10, and 9. These small groups limit the precision with which the observed counts can characterize event occurrence beyond the enrolled participants. The registry record does not report confidence intervals or a formal primary comparison with placebo.

The record describes the trial as single-center, but the center’s name is not reported. The official title calls the study double-blind, while the masking field records triple masking; the masked roles and explanation for the difference are not reported in the registry record. The randomization procedure, baseline characteristics, and detailed participant flow are also not reported.

The operational details of dose escalation, the investigators’ sample-size justification, and a prespecified statistical analysis plan are not reported in the registry record. Nor are missing-data procedures, multiplicity handling, or sensitivity analyses reported. The primary outcome’s timing definition does not establish causation, and the posted counts are not accompanied by inferential results.

Lastly, the primary outcome addresses short-term local safety, not immune response or protection. Although secondary outcomes are listed, their specific results are not reported in the registry record. These limitations confine interpretation to the observed counts and safety summaries recorded for this study.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Vaccine Treatment for Ebola Virus in Healthy Adults (V920-001) — NCT02269423.
• Registry record last updated 2019-10-23; status last verified 2019-10.
• Results first posted 2019-10-23.
• 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.

19. Record Summary

NCT02269423 is a completed Phase 1 randomized, single-center, placebo-controlled, dose-escalation study of V920, also identified as BPSC-1001 and VSVΔG-ZEBOV, in healthy adults. The registry reports enrollment of 39 participants. The primary endpoint was the number of participants with one or more solicited local TEAEs through 14 days postvaccination.

The posted primary counts were 8 participants in the 3x10^6 pfu cohort, 8 in the 2x10^7 pfu cohort, 10 in the 1x10^8 pfu cohort, and 3 in the placebo cohort. Serious adverse event counts and deaths were 0 in each cohort. The registry record does not report inferential comparisons for the primary endpoint, confidence intervals, or the statistical plan details needed to assess such comparisons.