A Phase II Study on Immunogenicity and Safety of MVA-BN® (IMVAMUNE™) Smallpox Vaccine in Subjects With Atopic Dermatitis: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Phase II Study on Immunogenicity and Safety of MVA-BN® (IMVAMUNE™) Smallpox Vaccine in Subjects With Atopic Dermatitis (NCT00316602), a non-randomized phase 2 study. The primary outcome is Percentage of Participants With Seroconversion by ELISA.

2. Clinical Question

The study therefore asks whether an antibody response was observed in the defined participant groups after vaccination, and how the recorded safety experience differed between them. Because treatment was not randomized and every group received the vaccine, a between-group contrast does not isolate a vaccine effect against no vaccination. It describes outcomes in these enrolled groups under the study conditions. The record does not report the numerical estimates or confidence intervals needed to quantify the primary comparison.

3. Trial Design

This was a multicenter, open-label, controlled Phase II study with parallel groups and non-randomized allocation. The registry lists an enrollment of 632. Participants were classified as healthy or as having diagnosed atopic dermatitis; both groups received two doses of MVA-BN. The record gives a study start of 2006-07, primary completion of 2009-11, and status of completed.

The design is controlled in the sense that outcomes were considered across distinct groups, but the groups differ by atopic dermatitis status and were not assigned at random. The healthy participants therefore provide a reference group for describing outcomes, not an untreated control for estimating vaccination effects. Differences between groups could reflect their underlying characteristics as well as the condition used to define the groups. The registry record does not report methods used to adjust for such differences.

Masking was listed as none, so the trial was open-label. The record does not describe masking of outcome assessors or laboratory staff. It lists a per-protocol population for the primary endpoint, but does not report the eligibility rules, exclusions, or participant counts in that analysis population. Those details matter because the enrollment figure does not establish how many participants contributed data to each endpoint.

The primary endpoint was seroconversion by ELISA at week 6. The registry also lists secondary immune-response measures based on ELISA, PRNT, and ELISPOT, as well as adverse-event outcomes. It lists 12 outcome measures overall and one analysis entry. The statistical analysis plan, any prespecified adjustment for group differences, and the rationale for the enrollment target are not reported in the registry record. The primary endpoint estimates and their confidence intervals are also not reported there, limiting interpretation of the study’s immunogenicity comparison.

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: Per Protocol Set

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: Safety Analysis Set

6. Primary Endpoint

The registry lists the primary outcome as Percentage of Participants With Seroconversion by ELISA, measured over week 6.

The primary endpoint is the percentage of participants with seroconversion by enzyme-linked immunosorbent assay, or ELISA, at week 6. It is a binary outcome at the participant level: each participant with available data is classified according to whether the specified seroconversion criterion was met. The registry states that percentages are based on participants with data available and identifies the per-protocol set as the analysis population.

The definition accounts for baseline antibody status. For initially seronegative participants, seroconversion means antibody titers reaching at least the stated detection limit of 50. For initially seropositive participants, it means a titer at least double the baseline titer. This definition lets the endpoint capture a new detectable response in one baseline group and a rise from baseline in the other.

Seroconversion is used as an immunogenicity measure because it expresses the proportion of participants meeting a prespecified antibody-response criterion. It is not a direct measure of clinical protection or of disease outcomes. The registry specifies a 95% confidence interval as the dispersion measure, but the primary endpoint estimate and interval are not reported in the registry record. As a result, the recorded endpoint definition can be described, but the magnitude and precision of the observed response cannot be evaluated from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The statistical methods that can be described are limited to the endpoint definitions and analysis details recorded in the registry. The primary outcome is a participant-level binary measure: seroconversion either meets the stated definition or it does not. A percentage expresses the share of participants with available data who meet that definition. The registry identifies the per-protocol set as the population for the primary endpoint and specifies a 95% confidence interval. It does not report the actual percentage, interval limits, or a detailed analysis procedure.

What does a confidence interval describe?

In general, a confidence interval communicates the uncertainty around an estimated quantity under the statistical model and sampling assumptions used. It is not a guarantee that the true value lies inside a particular calculated interval. For a binary percentage, the interval is especially useful alongside the estimate: the percentage gives the observed response level, while the interval gives information about its precision. The registry’s reference to a 95% confidence interval does not reveal how it was calculated. The specific interval method is not reported in the registry record.

Why does the analysis population matter?

The per-protocol set is the stated population for the primary endpoint. In general, a per-protocol analysis includes participants meeting protocol-defined requirements, but the registry does not give the requirements used in this study. The size and composition of that analysis set are also not reported. This matters because the enrolled total of 632 is not necessarily the number contributing to the primary endpoint. The endpoint description says the percentage is based on participants with data available, but does not explain how unavailable data were handled or whether the available-data population differed between groups.

How should the group comparison be understood?

Allocation was non-randomized, and both groups received two doses of the vaccine. The comparison is consequently observational with respect to atopic dermatitis status. In general, random allocation helps balance both measured and unmeasured participant characteristics between groups; without it, group contrasts can reflect differences other than the characteristic defining the groups. That concern does not make a descriptive contrast unusable, but it limits causal interpretation. The registry record does not report statistical adjustment for baseline differences or the covariates considered.

There is no untreated or placebo group in the listed design. A comparison between vaccinated participants with atopic dermatitis and vaccinated healthy participants cannot on its own separate vaccine-associated responses from background changes, nor can it estimate outcomes in the absence of vaccination. The registry describes an immunogenicity and safety comparison between participant groups, and interpretation should stay within that scope.

What is the role of the endpoint definition?

The seroconversion rule incorporates baseline antibody status. For initially seronegative participants it requires titers at or above the detection limit of 50; for initially seropositive participants it requires a titer at least double baseline. Using a rule tied to baseline status makes the endpoint interpretable for participants starting from different antibody levels. It also means that the binary outcome compresses the underlying antibody measurements into a response classification. The registry separately lists geometric mean titers and other immune measures, but their numerical results are not reported in the registry record.

Why can outcome multiplicity matter?

When a study evaluates multiple outcomes or makes multiple statistical comparisons, the chance of at least one apparently notable finding can increase if each is assessed independently. General approaches to this issue include prespecifying a primary endpoint, adjusting for multiple comparisons, or treating secondary analyses as exploratory. The registry designates a primary endpoint and lists 12 outcome measures, but does not report a multiplicity strategy. It also does not report the complete analysis plan, the number of statistical tests performed, or whether secondary outcomes were intended to be confirmatory or exploratory. The listed count of one analysis entry is not enough to establish how all outcomes were analyzed.

What can the safety counts tell readers?

Safety outcomes are event counts among participants at risk. The registry records serious adverse events in each group and also lists other adverse-event measures. In general, counts need their relevant denominators and definitions to be interpreted; they do not establish causation. A participant may have an event for reasons unrelated to an intervention, and an event recorded after vaccination is not automatically an event caused by vaccination. The registry does not report a causal assessment method or detailed follow-up information for these events. The listed serious-event term percentages are not accompanied by sufficient context to support a detailed comparison.

Finally, no sample-size justification, interim-analysis plan, or detailed model specification is reported in the registry record. These omissions prevent assessment of the planned precision or the full inferential strategy. The absence of a posted numerical primary result is more fundamental: confidence intervals and comparisons cannot be reconstructed without the underlying endpoint estimates and denominators. Statistical interpretation should therefore distinguish clearly between methods that the record specifies, methods that are generally relevant, and details that remain unreported.

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("Healthy Participants", "Atopic Dermatitis Participants")
n      <- c(194, 257)
events <- c(191, 250)
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  Healthy Participants  194  191  98.5  95.5  99.7  95.6  99.5  95.6  99.4
ARM  Atopic Dermatitis Participants  257  250  97.3  94.5  98.9  94.5  98.7  94.5  98.7

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 12 outcome measures, including the primary ELISA seroconversion endpoint and secondary immune-response and safety outcomes. It identifies the primary analysis population as the per-protocol set and says the primary percentage is based on participants with data available. These details identify some aspects of the analysis, but do not specify how multiplicity was handled across outcomes or comparisons. A multiplicity adjustment, a hierarchy among endpoints, and the intended confirmatory or exploratory status of secondary analyses are not reported in the registry record.

Missing-data methods are also not reported. The available-data wording indicates that the primary percentage uses participants with endpoint data, but it does not say how many lacked data, why data were unavailable, or whether any imputation or sensitivity analysis was used. Without those details, readers cannot assess whether missingness could have affected the estimated response or whether the analysis set was comparable between groups.

The record names the per-protocol set but does not give its definition or size. It does not report an intention-to-treat analysis for the primary endpoint. The relationship between the enrollment of 632 and the analyzed endpoint population is therefore unclear. The statistical analysis plan, including any prespecified handling of missing observations, is not reported in the registry record. These limitations concern transparency about analysis choices; they do not establish that a particular method was or was not used outside the information recorded.

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 2% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: extraocular muscle paresis (0.4%), head injury (0.4%), loss of consciousness (0.4%), panic attack (0.4%), neurosis (0.3%).

The registry records serious adverse events in three of 282 healthy participants and three of 350 participants with atopic dermatitis. It records zero deaths in each group. These are counts among participants listed as at risk; they should be read as descriptive safety information for the study groups, not as proof that an event was caused by vaccination. The registry record does not report a method for judging event causality.

The record also lists serious-event terms with percentages: Extraocular muscle paresis, Head injury, Loss of consciousness, and Panic attack are each listed as 0.4%; Neurosis and Asthma are each listed as 0.3%. It does not provide enough accompanying detail to establish how these term-level percentages relate to the group-level counts or to support a comparison between groups. They should not be combined or treated as mutually exclusive categories based on the information recorded.

Safety counts depend on how events were defined, collected, and followed. The registry record does not report all such details, nor does it give a full account of event timing or participant-level patterns. The counts therefore describe what is listed, while leaving important context for causal and comparative interpretation unreported.

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

The registry record documents a study designed to examine immune responses and safety in vaccinated participants with atopic dermatitis and vaccinated healthy participants. It defines the primary immune-response endpoint and identifies the time point, assay, and analysis population. It also records selected serious adverse-event counts. Those details clarify what the study set out to measure and provide a limited description of the safety information posted.

The record does not report the numerical primary endpoint results. Consequently, it does not show the percentage of participants who seroconverted by ELISA in either group, the confidence intervals, or the size and precision of the group contrast. The endpoint definition alone cannot establish the magnitude of an observed immune response. Likewise, without full outcome estimates, a reader cannot determine whether secondary immune measures were consistent with the primary measure.

The design also places limits on what a group difference could mean. Participants were not randomized, and both groups received two vaccine doses. A contrast between the groups would describe outcomes by atopic dermatitis status in this study, not the difference between vaccination and no vaccination. Non-random allocation also means that other group characteristics could contribute to any observed contrast. The registry does not report adjustment methods that would help address that concern.

The posted serious adverse-event counts are descriptive. They do not, on their own, establish causality, rule out uncommon risks, or establish that the groups had identical risk profiles. Zero recorded deaths in the listed groups is a description of this study record, not evidence about outcomes outside the study or a guarantee about future experience.

In short, the record supports an account of the trial question, design, endpoint definition, and selected safety figures. It does not support a numerical conclusion about the primary immune response because the primary results are not reported in the registry record. No treatment recommendation follows from these registry entries.

14. Why This Trial Matters Statistically

This trial is statistically informative as an example of the distinction between a clearly defined endpoint and an interpretable result. The registry specifies seroconversion by ELISA at week 6, defines the response in relation to baseline antibody status, and names a 95% confidence interval as the dispersion measure. Yet without the estimate and interval, the endpoint cannot answer how frequent the response was or how precisely it was measured. A complete endpoint definition is valuable, but it cannot substitute for reported results.

The study also illustrates why the nature of a comparator matters. Both groups received MVA-BN, while their defining difference was atopic dermatitis status. Because allocation was non-randomized, the comparison is not equivalent to a randomized treatment contrast. This distinction shapes the questions that can be addressed and the strength of causal claims that could follow from any observed difference.

Finally, the registry includes multiple immune and safety outcomes, while leaving the multiplicity plan, missing-data handling, analysis-set details, and sample-size justification unreported. These are not merely technical details: they affect how readers judge precision, robustness, and the risk of selective emphasis among results. The posted safety counts add useful descriptive information, but interpretation still depends on event definitions and context. Together, the available record highlights how transparent reporting of estimates, uncertainty, analysis populations, and statistical plans is essential for evaluating a clinical study.

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 most direct limitation is that numerical results for the primary endpoint are not reported in the registry record. The endpoint definition and requested dispersion measure are present, but the response percentages and confidence interval limits are absent. The record also does not provide group-specific denominators for the primary analysis, so the enrollment total cannot be used as a substitute for the analyzed sample size.

The non-randomized design is a further limitation for comparative interpretation. Participants were grouped by atopic dermatitis status, and both groups received the vaccine. The record does not report whether baseline characteristics differed, or whether adjustment was made for potential group differences. Open-label status is recorded, but masking of laboratory personnel or assessors is not described.

Several analysis details remain unreported: the definition and size of the per-protocol set, the handling of missing endpoint data, the sample-size justification, any interim analyses, the statistical analysis plan, and any multiplicity strategy. Although the record says primary percentages use participants with data available, it gives no missing-data counts or sensitivity analyses. The relationship between enrollment and the endpoint analysis population is therefore unclear.

For safety, the record provides selected serious-event counts and terms but does not report detailed event timing, causality assessment, or enough context to make term-level percentages a full comparative safety analysis. These limitations restrict what can be concluded from the registry record; they do not establish what analyses may have appeared elsewhere.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: A Phase II Study on Immunogenicity and Safety of MVA-BN® (IMVAMUNE™) Smallpox Vaccine in Subjects With Atopic Dermatitis — NCT00316602.
• Registry record last updated 2019-01-09; status last verified 2018-12.
• Results first posted 2019-01-09.
• 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

NCT00316602 is a completed, multicenter, open-label, non-randomized Phase II study with parallel groups. It enrolled 632 participants and compared healthy participants with participants who had diagnosed atopic dermatitis; both groups received two doses of MVA-BN, also called IMVAMUNE. The primary endpoint was the percentage with seroconversion by ELISA at week 6, analyzed in the per-protocol set and described with a 95% confidence interval.

The registry record defines seroconversion and lists secondary immune-response and safety outcomes. It records serious adverse events in three of 282 healthy participants and three of 350 participants with atopic dermatitis, with zero deaths in each group. Numerical primary endpoint results and key analysis details, including missing-data and multiplicity methods, are not reported in the registry record.