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 Study of Japanese Encephalitis Chimeric Virus Vaccine (JE-CV) in Children Previously Immunized With JE-CV (NCT01190228), a randomized phase 3 study. The primary outcome is Percentage of Participants With JE Seroprotection Before and Following a Dose of Live Attenuated JE-CV.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01190228 |
| Phase | Phase 3 |
| Condition | Japanese Encephalitis, Varicella |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 454 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Sanofi Pasteur, a Sanofi Company |
| Results posted | Yes |
2. Clinical Question
Population
Children previously vaccinated with a single dose of JE-CV were studied alongside JE-CV-naïve control participants. The primary seroprotection assessment used the Per Protocol Analysis Set. The registry record does not provide further eligibility details or the number included in that analysis set.
Intervention
Previously vaccinated participants received a booster dose of JE-CV on Day 0. One group of JE-CV-naïve participants received a first dose of JE-CV on Day 0. The study also assessed safety after a single dose of JE-CV.
Comparator
JE-CV-naïve participants assigned to the control group received one dose of varicella vaccine on Day 0. Their data were not analyzed for the primary seroprotection outcome, as specified in the study protocol.
Primary question
What percentage of participants had JE virus neutralizing antibody titers meeting the seroprotection definition before vaccination and at Day 7 and Day 28 after JE-CV vaccination? The definition was a titer of at least 10, measured with a 50% plaque reduction neutralization test. The registry record does not report the percentages at these time points.
3. Trial Design
This was a completed phase 3, randomized, parallel-group trial with no masking reported. The registry lists enrollment of 454 participants and describes three groups: participants previously vaccinated with JE-CV who received a booster, JE-CV-naïve participants who received a first dose of JE-CV, and JE-CV-naïve participants who received varicella vaccine. The group descriptions distinguish participants by their previous JE-CV vaccination status as well as by the vaccine administered during the study.
The registry identifies randomization but does not report the allocation procedure, the groups or participants to which randomization applied, or whether allocation was balanced across the groups. It also does not report masking of participants, clinicians, laboratory staff, or outcome assessors beyond the overall designation of no masking. These details should not be inferred from the parallel design.
The stated objective was to describe JE immune status before and after JE-CV vaccination in previously vaccinated participants and in JE-naïve participants. The primary outcome concerns seroprotection before vaccination and at Day 7 and Day 28 after vaccination. Other objectives concerned solicited and unsolicited adverse events through 6 months after the last vaccination, and related serious adverse events and related deaths from 6 months to 5 years after vaccination in JE-CV-primed participants. The registry record does not specify the detailed visit schedule or the analysis methods for these objectives.
The registry gives a study start date of 2010-08-25 and a primary completion date of 2010-10-29. The study status is completed. Those dates describe the registered study timeline; they do not establish the duration of every participant’s safety follow-up.
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.
Before assignment: A total of 454 participants who met all inclusion criteria and no exclusion criteria were enrolled in Group 1 or randomized to Group 2 or Group 3 on Day 0. All except 4 participants in Group 1 were vaccinated as planned (345 participants in Group 1, 46 participants in Group 2, and 59 participants in Group 3).
Overall Study
| Stage | JE-CV Vaccine Booster | JE-CV Vaccine First Dose | Varicella Vaccine Group |
|---|---|---|---|
| STARTED | 349 | 46 | 59 |
| COMPLETED | 344 | 46 | 59 |
| NOT COMPLETED | 5 | 0 | 0 |
Reasons for not completing this period:
| Reason | JE-CV Vaccine Booster | JE-CV Vaccine First Dose | Varicella Vaccine Group |
|---|---|---|---|
| Protocol Violation | 4 | 0 | 0 |
| Withdrawal by Subject | 1 | 0 | 0 |
Analysis population for the primary outcome, as defined in the registry: Seroprotection against JE-CV vaccine was assessed in the Per Protocol Analysis Set. Data for Varicella Vaccine Group were not analyzed for this outcome measure as pre-specified in the study protocol.
5. Baseline Characteristics
The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.
| Characteristic | Unit | JE-CV Vaccine Booster | JE-CV Vaccine First Dose | Varicella Vaccine Group | Total |
|---|---|---|---|---|---|
| Participants analysed | 345 | 46 | 59 | 450 | |
| Age, Categorical: <=18 years | Participants | 345 | 46 | 59 | 450 |
| Age, Categorical: Between 18 and 65 years | Participants | 0 | 0 | 0 | 0 |
| Age, Categorical: >=65 years | Participants | 0 | 0 | 0 | 0 |
| Age, Continuous | Months | 39.6 (SD 1.71) | 39.3 (SD 1.99) | 39.3 (SD 2.09) | 39.5 (SD 1.79) |
| Sex: Female, Male: Female | Participants | 172 | 25 | 29 | 226 |
| Sex: Female, Male: Male | Participants | 173 | 21 | 30 | 224 |
| Region of Enrollment: Philippines | Participants | 345 | 46 | 59 | 450 |
6. Primary Endpoint
The registry lists the primary outcome as Percentage of Participants With JE Seroprotection Before and Following a Dose of Live Attenuated JE-CV, measured over Day 0 (pre-vaccination) and Day 7 and Day 28 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 percentage of participants classified as seroprotected against JE before and after a dose of live attenuated JE-CV. Antibody levels were measured using a 50% plaque reduction neutralization test, abbreviated PRNT50. The registry defines seroprotection as a neutralizing antibody titer of at least 10 (1/dilution). The specified assessments were on Day 0 before vaccination and on Day 7 and Day 28 after vaccination.
In general, an antibody threshold turns a continuous laboratory measurement into a binary classification: each participant either meets the stated seroprotection definition or does not. A percentage then describes the share meeting that definition within the analyzed population at a particular assessment. This type of endpoint makes the threshold-based status and its frequency the focus, rather than the exact distribution of antibody titers.
The endpoint is relevant to the study’s stated immune-response objective because it tracks the proportion reaching the registry’s antibody criterion at the specified times. It is not, by itself, a direct measurement of clinical disease prevention. The registry record does not report the percentage estimates, their uncertainty, or the number assessed at each time point, so the magnitude and precision of the endpoint cannot be evaluated from the record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry describes a seroprotection endpoint and its measurement, but the actual percentages at Day 0, Day 7, and Day 28 are not reported in the registry record. Consequently, the posted information does not establish how common seroprotection was at any of those assessments, how it changed after vaccination, or how the groups compared. The absence of those estimates also means there is no reported uncertainty interval or test result to interpret for the primary outcome.
The study included participants with different prior JE-CV vaccination histories and different assigned vaccines. Those groups address distinct descriptive questions: immune status after a booster in previously vaccinated participants, immune status after a first JE-CV dose in naïve participants, and a varicella-vaccine control group. The registry explicitly says that the varicella group was not analyzed for the primary seroprotection outcome. It would therefore be inappropriate to treat it as a direct primary-endpoint comparison based on this record.
In general, a percentage estimate should be read together with its denominator and a measure of uncertainty. The percentage describes the observed proportion in the analyzed sample, while an uncertainty interval indicates how imprecisely that proportion may estimate the corresponding population quantity. Neither the endpoint percentages nor such intervals are included in the registry record for this record. No conclusion about the size or precision of an immune response can be drawn from the endpoint definition alone.
The safety summary lists participants with serious adverse events and other adverse events by group, along with deaths. These counts are descriptive and are not accompanied in the registry record by inferential comparisons, detailed timing, or a full account of event attribution. Counts alone do not establish whether group differences are meaningful, nor whether an event was caused by vaccination. The related-event follow-up objective is described, but the available safety summary does not provide enough detail to connect each listed event to that objective or its follow-up period.
Overall, the registry record supports a description of the trial’s question, design, endpoint definition, and selected safety counts. It does not provide the primary endpoint results needed to assess observed seroprotection at the specified visits. The distinction is important: a clearly defined outcome is not itself a result, and a completed trial status does not fill in unreported outcome estimates.
9. Statistical Methods Explained
The primary outcome is a binary classification summarized as a percentage. For each assessment, the numerator would be the number of participants who met the seroprotection definition, and the denominator would be the number assessed in the relevant analysis population. This is a general explanation of how a binary percentage is formed; the registry record does not report the endpoint numerators, denominators, or percentages.
What does the antibody threshold mean?
The registry defines seroprotection using a neutralizing antibody titer of at least 10 (1/dilution), measured by PRNT50. Applying a threshold gives a clinically interpretable category for analysis, but it also discards information about how far an individual’s titer lies above or below that threshold. Two participants with different titers can fall into the same category, while measurements close to the threshold may be sensitive to measurement variability. These are general properties of threshold-based outcomes; the registry does not report individual titers or information about measurement variability.
How should repeated assessments be understood?
The endpoint is assessed on Day 0, Day 7, and Day 28. These time points describe status before and after vaccination, so the outcome has a repeated-measure structure at the participant level. In general, comparisons across visits should account for the fact that measurements from the same participant are related rather than independent. The registry identifies the time points but does not report the statistical method used to analyze changes across them, whether participants with measurements at multiple visits were analyzed together, or whether the primary inference concerned a specific change or a particular visit.
A percentage at each visit and a within-participant change answer different questions. The first describes the proportion meeting the threshold at that assessment. A change analysis would describe how status differed over time, potentially accounting for the paired observations. Without the posted estimates and analysis details, it is not possible to determine which contrast was emphasized or how any correlation between visits was handled.
What would precision describe?
In general, a confidence interval expresses the uncertainty around an estimated quantity under a stated statistical procedure. For a percentage, it helps readers distinguish a precise estimate from one that is compatible with a broad range of underlying proportions. A confidence interval does not guarantee that the true value lies within it, and its interpretation depends on the design and analysis assumptions. No confidence intervals for the primary endpoint are reported in the registry record, so its precision cannot be assessed.
Similarly, a p-value, if reported, would address compatibility between data and a specified null model under its assumptions; it would not measure the size or importance of an effect. The registry record does not report primary-endpoint analyses or p-values. The absence of these values should not be replaced by an inference from the study’s phase, completion status, or endpoint definition.
How do the planning assumptions differ from trial results?
The registry describes planning illustrations based on the observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The effect to detect is expressed as a stated fraction of the observed effect. These assumptions describe hypothetical planning calculations; they do not establish the trial’s original design rationale, actual allocation, or achieved statistical power. The registry record does not report a sample-size justification for the trial. Planning calculations are not observed power, and they cannot substitute for the primary outcome estimates.
In general, a planning sample size depends on the target effect, variability or event frequency, significance level, desired power, allocation, and analysis method. Changing an assumed effect changes the planning result. Here, the observed endpoint effect and numerical planning results are not reported in the registry record, so no planning value can be evaluated or interpreted in the registry record.
Why does the analysis population matter?
The registry states that the seroprotection outcome was assessed in the Per Protocol Analysis Set. Such a population generally includes participants who met specified protocol requirements, but the exact rules for this set are not reported. In general, estimates from a per-protocol population describe participants meeting those requirements and may differ from estimates based on all randomized participants. The size and composition of the analysis set, exclusions, and handling of missing measurements are not reported in the registry record. These details are needed to understand precisely which participants contribute to any percentage.
The registry’s endpoint definition and scheduled assessments are therefore useful for understanding what the study intended to measure, while the absent estimates and analytic details limit interpretation of what it found. Statistical methods can clarify what an estimate would mean, but they cannot recover results not reported in the record.
10. Multiplicity, Missing Data and Analysis Populations
The primary seroprotection endpoint includes assessments at Day 0, Day 7, and Day 28. The study also describes immune-status objectives in previously vaccinated and JE-naïve participants, alongside a separate varicella-vaccine group that was excluded from the primary endpoint analysis. Multiple groups and assessment times can create more than one possible summary or comparison. In general, when many statistical tests are conducted, the chance of at least one apparently unusual result can increase unless the analysis plan addresses multiplicity.
The registry record does not report a testing hierarchy, multiplicity adjustment, prespecified primary contrast, or detailed statistical analysis plan. It is therefore not possible to determine whether the study designated a single inferential comparison or how any family of comparisons was handled. The description of the endpoint alone should not be taken as evidence that multiplicity was or was not controlled.
Missing-data handling is also not reported. The endpoint is defined for three assessments, but the record does not state how absent measurements, withdrawals, protocol deviations, or participants lacking evaluable laboratory results were handled. It does not provide denominators at each visit or explain whether any imputation method was used. In general, missingness can affect a percentage if the participants with observed measurements differ from those without them; the direction and size of any such effect depend on the circumstances.
The registry names the Per Protocol Analysis Set for the primary endpoint but does not define its membership or report the number analyzed. It also does not describe an intention-to-treat analysis or provide a comparison of analysis populations. These omissions limit assessment of potential selection from exclusions and of how completely the reported population would represent enrolled participants. Since the primary percentages themselves are not reported in the registry record, the impact of multiplicity or missing observations cannot be quantified.
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 |
|---|---|---|---|
| JE-CV Vaccine Booster | 3 | 345 | 0.9% |
| JE-CV Vaccine First Dose | 0 | 46 | 0.0% |
| Varicella Vaccine Group | 0 | 59 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| JE-CV Vaccine Booster | 0 of 345 |
| JE-CV Vaccine First Dose | 0 of 46 |
| Varicella Vaccine Group | 0 of 59 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5.00% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| JE-CV Vaccine Booster | 73 of 345 |
| JE-CV Vaccine First Dose | 13 of 46 |
| Varicella Vaccine Group | 12 of 59 |
Most frequent serious adverse event terms
| Event term | Organ system | JE-CV Vaccine Booster | JE-CV Vaccine First Dose | Varicella Vaccine Group |
|---|---|---|---|---|
| Dengue fever | Infections and infestations | 2 of 345 | 0 of 46 | 0 of 59 |
| Febrile convulsion | Nervous system disorders | 1 of 345 | 0 of 46 | 0 of 59 |
Most frequent non-serious adverse event terms
| Event term | Organ system | JE-CV Vaccine Booster | JE-CV Vaccine First Dose | Varicella Vaccine Group |
|---|---|---|---|---|
| Injection site Pain | General disorders | 73 of 345 | 13 of 46 | 12 of 59 |
| Malaise | General disorders | 49 of 345 | 6 of 46 | 6 of 59 |
| Fever | General disorders | 49 of 345 | 1 of 46 | 9 of 59 |
| Headache | Nervous system disorders | 41 of 345 | 5 of 46 | 8 of 59 |
| Upper respiratory tract infection | Infections and infestations | 37 of 345 | 3 of 46 | 6 of 59 |
| Injection site Erythema | General disorders | 29 of 345 | 1 of 46 | 4 of 59 |
| Myalgia | Musculoskeletal and connective tissue disorders | 19 of 345 | 2 of 46 | 2 of 59 |
| Injection site Swelling | General disorders | 19 of 345 | 0 of 46 | 1 of 59 |
| Rhinitis | Infections and infestations | 12 of 345 | 1 of 46 | 3 of 59 |
Serious events with the highest arm-level rate: dengue fever (0.6%), febrile convulsion (0.3%).
The registry safety summary lists serious adverse events for three groups: 3 participants among 345 at risk in the JE-CV booster group, 0 among 46 at risk in the JE-CV first-dose group, and 0 among 59 at risk in the varicella group. It lists 0 deaths in each group. These are descriptive counts with their stated at-risk denominators; they are not adjusted comparisons between groups.
The record also lists Dengue fever (0.6%) and Febrile convulsion (0.3%) among the top serious terms. It does not give enough detail in the available safety summary to assign those terms to a particular group, explain their denominators, or establish their relationship to vaccination. A listed event is not necessarily an event caused by the study vaccine. The registry’s objectives mention solicited and unsolicited adverse events through 6 months after the last vaccination and related serious events and deaths over a longer follow-up period in JE-CV-primed participants. The timeframe represented by each displayed safety count is not specified in the record, so the counts should not be assumed to cover every stated follow-up objective.
In general, safety counts are interpreted with their time window, event definitions, follow-up completeness, and attribution criteria. Those details are not reported, and the counts alone do not support a causal conclusion.
12. What the Result Does, and Does Not, Mean
The registry record documents a trial designed to describe JE seroprotection after vaccination in children with different prior JE-CV vaccination histories. It specifies a laboratory assay, an antibody threshold, and the assessments at Day 0, Day 7, and Day 28. Those details define the primary question and make clear what would be needed to interpret the immune-status outcome.
However, the primary endpoint percentages are not reported in the registry record. Readers therefore cannot determine from this information what proportion met the threshold at baseline or after vaccination, how the proportions changed, or how precisely they were estimated. The record also does not provide the statistical comparisons needed to evaluate differences between the booster and first-dose JE-CV groups. The varicella group was not analyzed for this endpoint.
The immune endpoint is an antibody-based measure. In general, meeting a laboratory threshold is not equivalent to demonstrating a particular clinical outcome. The record’s endpoint definition does not by itself establish protection against disease, duration of protection, or comparative clinical benefit. No such conclusion should be inferred from the stated assay and threshold alone.
The safety summary offers selected counts of serious adverse events, other adverse events, and deaths by group. These figures describe the recorded counts and denominators, but the available details do not establish event causality, comparative risk, or the completeness of long-term follow-up. The reported zero death counts are a description of the safety summary, not proof that no relevant event occurred outside the summary’s scope or follow-up.
In general, a trial’s completed status means its registered study status is complete; it does not ensure that every outcome estimate, analysis, or uncertainty measure appears in the registry record. The useful conclusion from this record is therefore limited: the study’s design and measurement framework are described, and selected safety counts are listed, but the primary numerical immune-response results are not reported. Interpretation should remain bounded by that distinction.
13. Why This Trial Matters Statistically
This trial is statistically notable for separating participants by prior JE-CV exposure. The booster group had previously received JE-CV, while the first-dose group was JE-CV-naïve. Those histories are central to interpreting immune status: a post-vaccination percentage in a previously vaccinated group addresses a different descriptive situation from one in a naïve group. The varicella group provides a separate vaccine control, but it was not included in the primary seroprotection analysis.
The endpoint is measured repeatedly around vaccination, so the time dimension matters as much as the antibody threshold. Baseline status and post-vaccination status are not interchangeable summaries. A complete interpretation would need the percentages, participant denominators, and uncertainty at the specified visits, along with a clear account of the planned comparisons. The registry record defines the visits but does not report those results or analysis details.
The study also illustrates why a biological measurement should be interpreted according to the outcome it actually represents. Here, seroprotection is operationalized using a neutralizing antibody threshold. That provides a clear binary endpoint, but statistical conclusions about that endpoint do not automatically answer broader questions about clinical outcomes or long-term persistence.
Finally, the safety summary shows why counts need context. Group denominators are listed, but the relevant follow-up period, detailed event attribution, and full analysis are not. Clear statistical reporting would connect each count to its population, observation period, and event definition. The registry record leaves some of those details unreported, making careful limits on interpretation especially important.
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 the primary outcome is that the registry record does not report the seroprotection percentages at Day 0, Day 7, or Day 28. It also does not report confidence intervals, participant denominators at each assessment, or inferential analyses. The outcome is therefore defined, but its observed magnitude and precision cannot be evaluated.
The stated analysis population is the Per Protocol Analysis Set, yet its inclusion rules, size, and exclusions are not described. Missing measurements and their handling are not reported. The record also does not specify a primary contrast, a multiplicity strategy, or the statistical model used for repeated assessments. These gaps prevent a detailed assessment of how the outcome was analyzed.
Although the trial is identified as randomized, the registry does not describe the allocation procedure or which groups were randomized against one another. The study is listed as having no masking, and further information about masking at the laboratory or outcome-assessment level is not reported. These design details matter when judging the possibility of bias, but their effects cannot be determined from the record.
The safety information is limited to selected counts and top serious-event terms. The time window, event attribution, and relationship of the summary to the longer follow-up objective are not clear. The record does not report enough information to interpret the top-term percentages by group or to make causal comparisons.
Finally, the registry describes planning illustrations based on an observed effect but does not report a sample-size justification for the trial or numerical planning results in the registry record for this record. The planning assumptions should not be mistaken for the study’s actual design rationale or for observed evidence about precision.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Study of Japanese Encephalitis Chimeric Virus Vaccine (JE-CV) in Children Previously Immunized With JE-CV — NCT01190228.
- Registry record last updated 2022-03-28; status last verified 2022-03.
- Results first posted 2017-11-08.
- 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
This completed phase 3, randomized, parallel-group study enrolled 454 participants and evaluated JE-CV in children previously vaccinated with JE-CV and in JE-CV-naïve participants. The groups received a JE-CV booster, a first JE-CV dose, or varicella vaccine. The primary endpoint was the percentage meeting a PRNT50-based seroprotection definition at Day 0, Day 7, and Day 28; the varicella group was not analyzed for this endpoint.
The registry record describes the endpoint but does not report its percentages or statistical analyses. Its safety summary lists serious adverse event counts of 3 among 345, 0 among 46, and 0 among 59, with 0 deaths in each group. Further details needed to interpret the primary results, missing data, analysis methods, and safety follow-up are not reported in the registry record.