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 VA-006 Vaccinia Vaccine (ACAM2000) for the Production of VIGIV (NCT01158157), a na phase 3 study. The primary outcome is Percent of Participants With Adverse Events Related to ACAM2000 Vaccine Administration.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01158157 |
| Phase | Phase 3 |
| Condition | Smallpox Vaccine Adverse Reaction |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 25 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Emergent BioSolutions |
| Results posted | Yes |
2. Clinical Question
Population
Eligible plasma donors were enrolled in a study addressing smallpox vaccine adverse reactions. The registry reports enrollment of 25 participants. The primary outcome was assessed in the safety population, but further details about that population and its relationship to enrollment are not reported in the registry record.
Intervention
All eligible participants received ACAM2000, a smallpox vaccine. The study purpose was to vaccinate plasma donors so plasma could be collected for manufacturing Vaccinia Immune Globulin Intravenous (VIGIV).
Comparator
There was no comparator group. The study is recorded as single-group, with no allocation to different treatments and no masking. Its results therefore describe participants who received ACAM2000; they do not provide a like-for-like comparison with an untreated or differently treated group.
Primary question
The primary endpoint asks what percentage of participants had adverse events related to ACAM2000 administration during days 0 to 90 post-vaccination. The registry record does not post an analysis result for this endpoint, so its value cannot be stated from the available record.
3. Trial Design
This completed Phase 3 study evaluated ACAM2000 vaccination in a single group. The registry identifies 25 participants as enrolled and describes one arm, in which all eligible subjects received ACAM2000. Allocation is listed as not applicable, and masking is listed as none. These features make this a non-comparative study: there is no separate control arm against which to estimate a treatment difference.
The stated purpose was to vaccinate plasma donors and collect plasma for use in manufacturing VIGIV. The condition listed is smallpox vaccine adverse reaction. The study therefore has a specific donor and manufacturing context, while its primary endpoint concerns adverse events related to vaccine administration. It is not described as a trial comparing clinical outcomes between treatments.
The registry gives a study start date of 2010-09-13 and a primary completion date of 2012-02-14. Its status is completed. The primary outcome timeframe is days 0 to 90 post-vaccination, and the outcome population is described as the safety population. Details about eligibility criteria, the vaccination procedure beyond administration of ACAM2000, plasma collection procedures, follow-up completeness, and the protocol’s statistical plan are not reported in the registry record.
The record lists one outcome measure but no analyses. Consequently, the design and endpoint can be described, but no estimate of the primary endpoint or statistical test result can be presented. The adverse-event counts recorded separately do not substitute for an analysis of the primary endpoint unless the record explicitly identifies them as its results; it does not do so.
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 | Vaccination |
|---|---|
| STARTED | 25 |
| COMPLETED | 25 |
| NOT COMPLETED | 0 |
Analysis population for the primary outcome, as defined in the registry: Post-vaccination adverse events were assessed in the safety population.
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.
Population: A total of 61 subjects were screened for VA-006 study; 25 subjects satisfied the eligibility criteria and were percutaneously administered ACAM2000 vaccine, while 36 subjects were not eligible for the study and were not administered ACAM2000.
| Characteristic | Unit | Vaccination |
|---|---|---|
| Participants analysed | 25 | |
| Age, Categorical: <=18 years | Participants | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 25 |
| Age, Categorical: >=65 years | Participants | 0 |
| Sex: Female, Male: Female | Participants | 4 |
| Sex: Female, Male: Male | Participants | 21 |
| Region of Enrollment: United States | participants | 25 |
| Age | years | 47 (SD 9.1) |
6. Primary Endpoint
The registry lists the primary outcome as Percent of Participants With Adverse Events Related to ACAM2000 Vaccine Administration, measured over Days 0 to 90 post-vaccination.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | percentage of participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint is the percent of participants with adverse events related to ACAM2000 vaccine administration during days 0 to 90 post-vaccination. It is a binary participant-level outcome: a participant either meets the endpoint definition or does not. Reporting the percentage would describe how common the defined event was in the assessed safety population during the stated follow-up window.
This type of endpoint is used to summarize safety experience after vaccination. It can offer a direct description of the proportion of participants who had an event classified as related to administration, but its interpretation depends on how events were collected, defined, and judged to be related. Those operational details are not reported in the registry record.
The registry identifies the endpoint and its timeframe but does not post an analysis result for it. The adverse-event listing includes counts for serious and other adverse events, but it does not identify those counts as the primary endpoint result. The primary endpoint’s numerator, denominator, percentage, and any uncertainty estimate are therefore not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry describes a single-group study of ACAM2000 vaccination in 25 enrolled participants. Its primary question concerns the percentage of participants in the safety population who had adverse events related to vaccination during days 0 to 90 post-vaccination. Although the outcome is defined, the registry posts no analysis of it. The primary endpoint estimate and its precision are not reported in the registry record.
The adverse-event information lists 25 participants at risk for serious adverse events and 0 serious adverse events. It also lists 25 participants at risk for other adverse events and 15 affected. These are registry counts, not a comparative treatment effect. The record does not provide enough information to treat the count of other adverse events as the primary endpoint result, which specifically concerns events related to ACAM2000 administration.
Because there is no comparator group, the study cannot estimate how the observed event experience differs from what would have occurred without vaccination or under another intervention. In general, a single-group safety description can characterize events observed in the enrolled participants, but it cannot isolate a causal treatment effect from other explanations. The registry’s lack of masking is also relevant when considering how subjective event identification or relatedness judgments might be influenced; the methods used to assess events are not reported in the registry record.
No confidence interval, test result, or other inferential analysis is posted for the primary endpoint. In general, a confidence interval describes the range of values compatible with an estimate under the method’s assumptions; without an estimate and interval, the precision of the primary endpoint cannot be evaluated. The count data alone do not supply a reported uncertainty measure.
The sample-size assumptions describe a planning illustration using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. They specify detection of a stated fraction of an observed effect. Those assumptions do not describe this single-group design, and the record does not report a trial-specific sample-size justification. Any planning illustrations should not be read as evidence of observed power or as an analysis of the trial results.
Overall, the posted record supports a limited description of the study design, endpoint, and adverse-event counts. It does not support a numerical conclusion about the primary endpoint, a comparison with another treatment or no treatment, or a claim about the precision of the primary endpoint estimate.
9. Statistical Methods Explained
The outcome is binary at the participant level: the primary endpoint concerns whether a participant had an adverse event classified as related to ACAM2000 administration during the stated follow-up window. The registry describes the result in percentage terms, but it does not post a result for this endpoint. Without a numerator and denominator for the analyzed safety population, no endpoint percentage can be reported from the registry record.
What does a binary endpoint describe?
In general, a binary endpoint divides participants into two categories according to whether a defined event occurred. A percentage summarizes the share meeting the event definition in the population assessed. This is a descriptive summary, not automatically a causal estimate. In a single-group study, it reports experience in that group; a comparison with a separate control group would be needed to directly estimate a between-group difference.
The meaning of a binary safety endpoint also depends on event definitions and assessment procedures. For this study, the endpoint is described as adverse events related to ACAM2000 administration, and the timeframe is days 0 to 90 post-vaccination. The registry does not give further definitions, adjudication procedures, or detail on how relatedness was assigned. Such information matters because different event definitions or assessment practices can change which participants meet the endpoint.
Why does the design matter for interpretation?
This is a single-group study with no comparator, allocation, or masking. In general, a single-group proportion can describe the observed frequency within the studied group, but it cannot by itself separate the intervention’s contribution from other influences. Comparisons across groups can also be affected by differences in participant characteristics, follow-up, and event assessment. No such comparative estimate is posted for this study.
Masking can matter particularly when outcome assessment includes judgment, such as deciding whether an event is related to an intervention. With masking listed as none, participants and study personnel were not masked according to the registry field. The record does not describe safeguards or procedures used to assess events or relatedness, so the extent to which assessment could be influenced cannot be determined from the registry record.
What can be inferred from counts?
The adverse-event listing reports 0 serious adverse events among 25 participants at risk and 15 affected among 25 participants at risk for other adverse events. Counts are useful descriptive information, but they are not a substitute for a reported primary endpoint analysis. The record does not specify that the other adverse-event count consists only of events related to ACAM2000 administration. Nor does it post an uncertainty estimate for these counts. In general, uncertainty quantifies how much an estimate might vary across samples under a statistical model; a count without a reported interval or analysis does not convey that precision.
The registry lists one outcome measure and no analyses. It therefore does not report a statistical test, confidence interval, adjustment, or model for the primary endpoint. The statistical analysis plan, including whether any planned analysis was changed or omitted, is not reported in the registry record.
How should planning assumptions be read?
The sample-size assumptions describe a planning illustration, not the study’s reported analysis. They use a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect expressed as a fraction of an observed effect. These assumptions do not match the recorded single-group design. The record does not report that this was the trial’s design method or sample-size justification, and the illustration is not observed power.
In general, over-dispersion means that variability in data is greater than a chosen model expects. It can make standard errors too small if ignored, leading to confidence intervals that are too narrow or tests that reject too often. The registry does not identify an over-dispersion issue or describe a model for this binary endpoint, so no claim can be made about whether it was relevant to the analysis.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists one outcome measure and no analyses. It does not report a statistical analysis plan, a hierarchy of endpoints, or any procedure for controlling multiplicity. Multiplicity concerns the increased chance of a false-positive finding when several statistical tests or outcomes are examined. Since no analysis is posted and the record does not describe a testing strategy, it is not possible to determine whether multiplicity was addressed or relevant to the planned analyses.
Missing-data handling is not reported in the registry record. The endpoint is described for the safety population, but the record does not define how participants entered that population, report how many had endpoint assessments, or explain how incomplete follow-up was treated. Enrollment of 25 participants does not by itself establish that all were assessed for the endpoint throughout the stated timeframe.
In general, missing outcomes can affect an estimate if participants without recorded outcomes differ from those with observed outcomes. Statistical approaches to missing data rely on assumptions, and the appropriate interpretation depends on what was missing and why. Without the analysis population, missingness counts, and handling methods, the effect of missing data on this study’s endpoint cannot be evaluated.
The registry does not report whether any interim analyses were planned or conducted, whether the endpoint definition or analysis changed, or why no analyses are posted. These details are not reported in the registry record. Accordingly, the primary endpoint’s analyzed denominator, multiplicity approach, and missing-data strategy remain unclear.
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 |
|---|---|---|---|
| ACAM200 Vaccination Dose | 0 | 25 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| ACAM200 Vaccination Dose | 0 of 25 |
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 |
|---|---|
| ACAM200 Vaccination Dose | 15 of 25 |
Most frequent non-serious adverse event terms
| Event term | Organ system | ACAM200 Vaccination Dose |
|---|---|---|
| Vaccination complication | Injury, poisoning and procedural complications | 13 of 25 |
| Headache | Nervous system disorders | 2 of 25 |
| Injection site scab | General disorders | 1 of 25 |
The adverse-event listing records 0 serious adverse events among 25 participants at risk. For other adverse events, it records 15 affected among 25 participants at risk. These counts describe the entries in the registry; they do not establish a comparison with another group, because the study had no comparator.
The serious-event count should be read as a reported count, not as proof that serious events could not occur in other settings or populations. The registry does not provide an uncertainty estimate or further details about event definitions, collection, follow-up completeness, or assessment procedures. It also does not report the timing or nature of the other adverse events in the displayed adverse-event information.
The primary endpoint concerns adverse events related to ACAM2000 administration, whereas the adverse-event listing distinguishes serious from other events. The record does not establish that the 15 other adverse events were all considered related to vaccination or that they make up the primary endpoint. The primary endpoint analysis itself is not reported in the registry record. These counts should therefore be interpreted separately from that endpoint.
12. What the Result Does, and Does Not, Mean
The record describes a completed Phase 3, single-group study in which eligible participants received ACAM2000. Its stated purpose was to vaccinate plasma donors and collect plasma for manufacturing VIGIV. The registry identifies a primary safety endpoint covering days 0 to 90 post-vaccination, but it does not post an analysis result for that endpoint.
The adverse-event information reports 0 serious adverse events among 25 participants at risk and 15 affected among 25 participants at risk for other adverse events. These counts provide a limited description of the safety entries recorded. They are not a comparison with an alternative intervention, and the record does not clarify whether the count of other adverse events represents events considered related to ACAM2000.
The results do not establish the percentage of participants meeting the primary endpoint, because that analysis is not posted. They also do not provide a confidence interval or other measure of precision for the primary endpoint. In general, a confidence interval helps show how uncertain an estimate is; without a posted estimate and interval, the precision of the primary result cannot be assessed.
The single-group design also limits causal interpretation. Without a control group, the record cannot show how event experience would compare under a different intervention or without vaccination. The posted information therefore supports a description of the study and its recorded counts, but not a comparative estimate or a causal conclusion.
The study’s purpose concerns plasma collection for VIGIV manufacture. The registry record does not provide results about the manufacturing process or the quality or performance of VIGIV. Those matters should not be inferred from the vaccination and adverse-event information.
13. Why This Trial Matters Statistically
This study illustrates why a clearly stated endpoint and a posted endpoint analysis are both needed for statistical interpretation. The registry defines the primary outcome as the percentage of participants with adverse events related to ACAM2000 administration during days 0 to 90 post-vaccination. But the record posts no analysis of that outcome. A defined measure alone does not show its observed value or how precisely it was estimated.
The design is also important. With a single group and no comparator, the study can describe events observed among vaccinated participants, but it cannot estimate a between-group treatment difference. This distinction is central when interpreting safety evidence: a descriptive frequency and a comparative effect answer different questions.
The adverse-event counts show how separate listings should not be conflated with the primary endpoint. Serious and other adverse events are categorized in the safety listing, while the primary outcome specifically concerns events related to vaccine administration. The record does not state that the other-event count is the primary endpoint result. Keeping these definitions distinct avoids treating a relatedness endpoint as interchangeable with a broader adverse-event count.
Finally, the planning assumptions are not evidence of the actual study’s design or statistical analysis. They describe an illustration based on two-arm assumptions, whereas the registered study is single-group. Recognizing that mismatch helps prevent planning quantities from being misread as observed power, trial-specific justification, or evidence that the primary question was answered.
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 main limitation for interpreting results is that the primary endpoint is defined but not analyzed in the registry record. Its numerator, denominator, percentage, and precision are not reported. The record lists adverse-event counts, but does not identify them as the primary endpoint results or establish that the other adverse events were considered related to ACAM2000.
The single-group design provides no comparator. Consequently, the posted information cannot estimate a treatment difference or distinguish the vaccine’s contribution from other explanations for events. Masking is listed as none, and the record does not describe how events or relatedness were assessed.
Enrollment is reported as 25, and the adverse-event listing gives 25 participants at risk for both serious and other adverse events. The record does not explain how those at-risk counts relate to the endpoint’s safety population, nor does it report follow-up completeness or handling of missing outcomes. The statistical analysis plan, sample-size justification, interim analyses, and any changes to the planned analyses are not reported in the registry record.
The registry gives the study purpose as donor vaccination and plasma collection for VIGIV manufacturing, but it does not report manufacturing outcomes. The adverse-event information is also limited: further event descriptions, timing, and assessment details are not reported in the registry record. These limits constrain interpretation to the study design and the counts that are explicitly listed.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: VA-006 Vaccinia Vaccine (ACAM2000) for the Production of VIGIV — NCT01158157.
- Registry record last updated 2024-03-18; status last verified 2024-03.
- Results first posted 2019-03-26.
- 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
The registry identifies NCT01158157 as a completed Phase 3, single-group study sponsored by Emergent BioSolutions. The study enrolled 25 participants, and all eligible subjects in the single arm received ACAM2000. The stated purpose was to vaccinate plasma donors and collect plasma for manufacturing VIGIV.
The primary endpoint was the percent of participants with adverse events related to ACAM2000 administration during days 0 to 90 post-vaccination, assessed in the safety population. No analysis of this endpoint is posted. The adverse-event listing reports 0 serious adverse events among 25 at risk and 15 affected among 25 at risk for other adverse events.
There was no comparator, masking was listed as none, and the registry lists one outcome measure and no analyses. Details of the statistical plan, missing-data handling, endpoint assessment procedures, and the primary endpoint result are not reported in the registry record.