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 to Demonstrate Consistency of Three Lots of a Live-attenuated Chikungunya Virus Vaccine Candidate in Healthy Adults (NCT04786444), a randomized phase 3 study. The primary outcome is Geometric Mean Titer (GMT) of CHIKV-specific Neutralizing Antibodies as Determined by Microneutralization (μPRNT) Assay in Subjects Who Tested Negative for CHIKV Antibodies at Baseline.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT04786444 |
| Phase | Phase 3 |
| Condition | Chikungunya Virus Infection |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Double |
| Enrollment | 409 |
| Arms in the primary outcome | 3 |
| Lead sponsor | Valneva Austria GmbH |
| Results posted | Yes |
2. Clinical Question
Population
Healthy adults aged 18 to 45 years who tested negative for chikungunya virus antibodies at baseline were the population for the primary immunogenicity endpoint. The primary analysis population was per protocol: participants without major protocol deviations that could affect immune response. The study randomized 409 participants overall; the registry reports primary endpoint estimates for 122, 118, and 122 participants in the three lot groups.
Intervention
Participants received a single vaccination with the live-attenuated chikungunya virus vaccine candidate VLA1553 at the final dose. The study evaluated three manufacturing lots, identified as Lot 1, Lot 2, and Lot 3. The registry describes the intervention as a biological vaccine.
Comparator
The relevant comparisons are among the three VLA1553 lots. This was not a comparison of vaccine against placebo or against no vaccination. The registry record does not provide a separate control treatment or describe the individual lot groups beyond their lot labels.
Primary question
Among baseline-negative participants in the per-protocol immunogenicity population, what was the geometric mean titer of chikungunya virus-specific neutralizing antibodies on Day 29 after single vaccination for each lot? The study’s stated purpose was to demonstrate lot-to-lot consistency. The registry reports lot-specific GMTs and confidence intervals, but a prespecified consistency margin or formal statistical comparison is not reported in the registry record.
3. Trial Design
This was a prospective, randomized, double-blinded, multicenter Phase 3 study of VLA1553 in healthy adults aged 18 to 45 years. Its stated objective was to demonstrate consistency across three lots of the live-attenuated chikungunya virus vaccine candidate. Participants were assigned to parallel groups receiving VLA1553 Lot 1, Lot 2, or Lot 3. The study evaluated the vaccine at the final dose, given as a single vaccination.
The registry reports that 409 participants were randomized overall. For the primary endpoint, the per-protocol immunogenicity analysis included 122 participants in Lot 1, 118 in Lot 2, and 122 in Lot 3. Those analysis counts should not be treated as the overall number randomized to each group: the registry’s overall enrollment and primary endpoint analysis populations are different summaries. The per-protocol population excludes participants with major protocol deviations that could affect immune response.
Randomization is intended to reduce systematic differences between groups at allocation, while double blinding is intended to limit expectations affecting participant experience or outcome assessment. These are general design purposes; the registry record does not describe the randomization sequence, concealment procedures, or operational details of masking. It identifies the design as randomized, double-blinded, and parallel.
The primary endpoint was measured on Day 29 after the single vaccination. It was the GMT of chikungunya virus-specific neutralizing antibodies, measured using a microneutralization assay, among participants who tested negative for chikungunya virus antibodies at baseline. Secondary outcomes included other antibody-response measures and solicited injection-site and systemic reactions. The registry lists 17 outcome measures and 16 posted secondary outcomes. Detailed procedures for these secondary assessments are not reported in the registry record.
The study is listed as completed. Its start date and primary completion date are recorded as 2021-02-22 and 2021-07-22. The registry record does not report the planned allocation ratio, the sample-size justification, or a protocol-level description of the statistical analysis plan.
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 | VLA1553 Lot 1 | VLA1553 Lot 2 | VLA1553 Lot 3 |
|---|---|---|---|
| STARTED | 136 | 137 | 135 |
| COMPLETED | 121 | 120 | 123 |
| NOT COMPLETED | 15 | 17 | 12 |
Reasons for not completing this period:
| Reason | VLA1553 Lot 1 | VLA1553 Lot 2 | VLA1553 Lot 3 |
|---|---|---|---|
| Withdrawal by Subject | 4 | 7 | 2 |
| Lost to Follow-up | 11 | 9 | 10 |
| Subject would like to become pregnant | 0 | 1 | 0 |
Analysis population for the primary outcome, as defined in the registry: The Per-Protocol population used for immunogenicity analyses, is based on participants without major protocol deviations that could impact the immune response.
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 | VLA1553 Lot 1 | VLA1553 Lot 2 | VLA1553 Lot 3 | Total |
|---|---|---|---|---|---|
| Participants analysed | 136 | 137 | 135 | 408 | |
| Age, Continuous | years | 33.2 (SD 7.03) | 33.2 (SD 7.78) | 33.2 (SD 7.43) | 33.2 (SD 7.40) |
| Sex: Female, Male: Female | Participants | 75 | 76 | 72 | 223 |
| Sex: Female, Male: Male | Participants | 61 | 61 | 63 | 185 |
| Race/Ethnicity, Customized: American, Indian or Alaska Native | Participants | 4 | 1 | 0 | 5 |
| Race/Ethnicity, Customized: Asian | Participants | 6 | 5 | 7 | 18 |
| Race/Ethnicity, Customized: Black or African American | Participants | 21 | 22 | 19 | 62 |
| Race/Ethnicity, Customized: Native Hawaiian or other Pacific Islander | Participants | 0 | 1 | 0 | 1 |
| Race/Ethnicity, Customized: White | Participants | 103 | 106 | 106 | 315 |
| Race/Ethnicity, Customized: Other | Participants | 2 | 2 | 3 | 7 |
6. Primary Endpoint
The registry lists the primary outcome as Geometric Mean Titer (GMT) of CHIKV-specific Neutralizing Antibodies as Determined by Microneutralization (μPRNT) Assay in Subjects Who Tested Negative for CHIKV Antibodies at Baseline, measured over On Day 29 after single vaccination.
| Element | Registry entry |
|---|---|
| Result type | Geometric Mean |
| Measure of spread | 95% Confidence Interval |
| Unit | Geometric Mean Titer |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is the geometric mean titer of chikungunya virus-specific neutralizing antibodies measured by the μPRNT microneutralization assay on Day 29 after a single vaccination. The analysis population was restricted to participants who tested negative for chikungunya virus antibodies at baseline and met the per-protocol definition for immunogenicity analyses. That definition excludes participants with major protocol deviations that could impact immune response.
A neutralizing-antibody titer represents the dilution level at which serum can neutralize virus under the assay conditions. A GMT summarizes titers using a geometric rather than arithmetic average. In general, this is useful for measurements that are positive and can vary multiplicatively: the geometric mean is calculated on a logarithmic scale and then expressed on the original scale. It describes a group-level antibody response, not the titer of a typical individual in every respect.
The endpoint is relevant to a lot-consistency question because the study can compare the measured immune responses associated with the three vaccine lots. The posted estimates describe the GMT for each lot, with a 95% confidence interval. The confidence interval conveys uncertainty around each group estimate; it is not a range containing most individual participants’ titers.
The endpoint alone does not specify what degree of difference between lots would count as acceptable consistency. A prespecified equivalence or consistency margin, the formal decision rule, and a formal inferential comparison are not reported in the registry record. Thus, the GMTs provide descriptive information about the measured antibody response, but the registry outcome values alone do not establish whether a formal consistency criterion was met.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
On Day 29, the reported GMT was 2557.0 for VLA1553 Lot 1, with a 95% confidence interval from 2056.0 to 3180.0. For Lot 2, the GMT was 2768.0, with a 95% confidence interval from 2310.0 to 3316.0. For Lot 3, the GMT was 2614.0, with a 95% confidence interval from 2128.0 to 3210.0. These are estimates in the baseline-negative per-protocol immunogenicity population.
The three point estimates are on a similar scale, and their reported confidence intervals overlap. This is a descriptive observation, not a formal test of equality or consistency. Confidence-interval overlap does not by itself determine the result of a formal comparison, and the registry does not report a consistency margin or decision rule against which the lot estimates can be judged.
The reported analysis counts are 122 for Lot 1, 118 for Lot 2, and 122 for Lot 3. These are the numbers in the primary endpoint analysis, not the overall randomized enrollment of 409. The registry record does not explain in detail how participants moved from randomization into the per-protocol analysis population, or whether missing measurements or exclusions affected the estimates.
The estimates concern neutralizing-antibody titers at a particular post-vaccination time point. They do not, by themselves, describe antibody persistence beyond Day 29, clinical protection, or the likelihood of chikungunya infection. The registry lists additional immune-response outcomes, but the primary endpoint results should not be read as results for all those outcomes.
No p-value, confidence interval for a between-lot contrast, or other formal comparison result is reported in the registry record. Accordingly, the posted GMTs support a descriptive comparison of the three lots, but do not show the result of a prespecified statistical test of lot consistency. A claim that consistency was formally demonstrated would require the relevant analysis and its acceptance criteria, which are not reported in the registry record.
The estimates should also be understood in light of the analysis population. Per-protocol results describe participants who met the stated criteria for immunogenicity analyses, rather than necessarily all randomized participants. The registry says that major protocol deviations affecting immune response were excluded, but the exact exclusions and the handling of incomplete endpoint data are not reported in the registry record.
9. Statistical Methods Explained
For the primary endpoint, the registry reports a geometric mean titer and a 95% confidence interval for each of the three lots. The endpoint is a group summary of neutralizing-antibody titers measured by the μPRNT assay on Day 29 after a single vaccination. The estimates apply to baseline-negative participants in the per-protocol population. This group-specific reporting allows readers to inspect the estimated antibody response and the uncertainty around it for each lot.
What does a geometric mean summarize?
In general, a geometric mean is appropriate for positive measurements that vary multiplicatively or have a right-skewed distribution. The calculation takes logarithms of the individual measurements, averages those values, and transforms the average back to the original scale. This is a general explanation of the statistic; the registry record does not describe the exact data transformation or computational procedure used for this analysis.
A GMT is not an arithmetic average of the raw titers. Nor does it describe the spread of individual observations. The GMT is a central group estimate, while a separate measure of variability or individual-level data would be needed to describe how much participants’ titers differed from one another. The registry reports confidence intervals for the GMTs, not individual-level distributions.
How should the confidence intervals be read?
In general, a confidence interval expresses the precision of an estimate under the assumptions of the statistical procedure. A narrower interval indicates greater precision than a wider interval on the same scale, while a wider interval indicates more uncertainty about the estimated group value. A 95% confidence interval is not a statement that 95% of individual titers fall within its limits, and it is not a probability statement that the fixed parameter lies in the particular interval after the data have been observed.
The registry reports a separate interval for each lot. These intervals describe uncertainty around the lot-specific GMTs. They are not confidence intervals for differences between lots. A formal comparison would ordinarily report a contrast, such as a ratio of GMTs or a difference on an appropriate analysis scale, together with an uncertainty measure and a decision rule. Such a comparison is not reported in the registry record.
Why does the analysis population matter?
The primary endpoint uses the per-protocol population for immunogenicity analyses. The registry defines this population as participants without major protocol deviations that could impact immune response. This can be relevant because exclusions after randomization may change the group of participants contributing to an estimate. The randomized enrollment of 409 and the lot-specific endpoint counts therefore answer different questions: the first describes overall enrollment, while the latter describe the primary analysis populations. The registry does not list the reasons for every exclusion or provide a complete accounting of missing endpoint observations.
The baseline-negative restriction is also part of the endpoint definition. The reported results are not a summary of all enrolled participants regardless of baseline antibody status. They describe the defined subgroup used for the primary immunogenicity analysis.
What would a formal lot-consistency analysis require?
In general, a formal consistency analysis requires an explicit comparison and a prespecified criterion for an acceptable difference among products or lots. For example, a protocol may define a margin and evaluate whether uncertainty around the contrast lies within that margin. This is a general description of an approach, not a description of the analysis used in this study. The registry record does not report a consistency margin, a decision rule, or the result of a formal lot comparison. Similar point estimates and overlapping confidence intervals are not substitutes for those elements.
Randomization and blinding are design features, not statistical conclusions. Random assignment is generally used to reduce systematic allocation differences, and blinding can reduce influence from expectations in study conduct or assessment. The registry identifies the study as randomized and double-blinded, but does not describe the sequence-generation method, allocation concealment, or procedures for maintaining blinding. Those operational details are not reported in the registry record.
What can planning calculations tell readers?
In general, a sample-size planning illustration describes how many participants per arm might be needed under specified assumptions to detect a selected effect with a chosen power and significance level. The registry’s planning assumptions describe 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 are planning illustrations based on the observed effect, not the trial’s own design justification and not observed power.
The registry record does not report the trial’s sample-size justification or a planning comparison that fully represents a three-lot consistency design. The planning assumptions therefore should not be used to infer the protocol’s intended statistical method or whether the study was adequately sized for a formal consistency objective. Sample-size calculations depend on the target effect, variability assumptions, analysis method, and decision rule. Those details, beyond the stated illustration assumptions, are not reported in the registry record.
Finally, the registry lists no analyses in its analysis count, even though it reports outcome estimates. This means the posted endpoint values can be described, but a detailed statistical analysis report—including adjusted or unadjusted contrasts, model specifications, and multiplicity procedures—is not reported in the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 17 outcome measures and 16 posted secondary outcomes. These include neutralizing-antibody titers, seroprotection and seroconversion proportions, fold increases in antibody titer, and solicited injection-site and systemic reactions. When a study assesses multiple outcomes, the chance of at least one apparently notable result can increase if many tests are conducted. In general, multiplicity procedures can address that issue by adjusting testing or by specifying a hierarchy of outcomes. The procedure used for this study is not reported in the registry record.
The record identifies one primary endpoint: the Day 29 GMT among baseline-negative participants in the per-protocol immunogenicity population. However, it does not provide the full analysis plan, any planned hierarchy among outcomes, or details of whether the secondary outcomes were treated as confirmatory or exploratory. The registry’s analysis count is 0, and no formal analysis results for between-lot comparisons are listed.
Missing-data handling is not reported in the registry record. In particular, the record does not describe how missing Day 29 measurements were handled, whether any values were imputed, or how participants with incomplete follow-up were treated. The per-protocol population definition states that participants with major protocol deviations that could impact immune response were excluded, but it does not give a complete account of missing observations or exclusions.
The baseline-negative restriction and per-protocol definition also limit the population represented by the primary endpoint. The registry reports the relevant analysis counts, but does not provide a full participant flow or enough detail to assess the reasons for differences between randomized enrollment and the analyzed groups. These omissions make it difficult to evaluate the sensitivity of the estimates to missing data, exclusions, and choices among multiple outcomes.
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 |
|---|---|---|---|
| VLA1553 Lot 1 | 3 | 136 | 2.2% |
| VLA1553 Lot 2 | 2 | 137 | 1.5% |
| VLA1553 Lot 3 | 0 | 135 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| VLA1553 Lot 1 | 0 of 136 |
| VLA1553 Lot 2 | 0 of 137 |
| VLA1553 Lot 3 | 0 of 135 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 1% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| VLA1553 Lot 1 | 90 of 136 |
| VLA1553 Lot 2 | 91 of 137 |
| VLA1553 Lot 3 | 92 of 135 |
Most frequent serious adverse event terms
| Event term | Organ system | VLA1553 Lot 1 | VLA1553 Lot 2 | VLA1553 Lot 3 |
|---|---|---|---|---|
| Appendicitis | Infections and infestations | 1 of 136 | 1 of 137 | 0 of 135 |
| Abortion spontaneous | Pregnancy, puerperium and perinatal conditions | 1 of 136 | 1 of 137 | 0 of 135 |
| Cholecystitis acute | Hepatobiliary disorders | 1 of 136 | 0 of 137 | 0 of 135 |
Most frequent non-serious adverse event terms
| Event term | Organ system | VLA1553 Lot 1 | VLA1553 Lot 2 | VLA1553 Lot 3 |
|---|---|---|---|---|
| Fatique | General disorders | 53 of 136 | 49 of 137 | 55 of 135 |
| Headache | Nervous system disorders | 49 of 136 | 42 of 137 | 57 of 135 |
| Myalgia | Musculoskeletal and connective tissue disorders | 33 of 136 | 36 of 137 | 30 of 135 |
| Injection site pain | General disorders | 22 of 136 | 30 of 137 | 22 of 135 |
| Arthralgia | Musculoskeletal and connective tissue disorders | 24 of 136 | 22 of 137 | 26 of 135 |
| Nausea | Gastrointestinal disorders | 16 of 136 | 20 of 137 | 17 of 135 |
| Pyrexia | General disorders | 16 of 136 | 18 of 137 | 19 of 135 |
| Rash | Skin and subcutaneous tissue disorders | 2 of 136 | 8 of 137 | 6 of 135 |
| Vomiting | Gastrointestinal disorders | 3 of 136 | 7 of 137 | 3 of 135 |
| Neutropenia | Blood and lymphatic system disorders | 4 of 136 | 3 of 137 | 5 of 135 |
Serious events with the highest arm-level rate: appendicitis (0.7%), abortion spontaneous (0.7%), cholecystitis acute (0.7%).
The registry reports serious adverse event counts for the three lot groups. For Lot 1, 3 of 136 participants at risk were affected; for Lot 2, 2 of 137 were affected; and for Lot 3, 0 of 135 were affected. The registry also reports 0 deaths in each group. These counts describe what was recorded in the specified groups; they do not establish that an event was caused by the vaccination.
The record lists Appendicitis, Abortion spontaneous, and Cholecystitis acute among the top serious terms, each shown as 0.7%. It does not provide, alongside these terms, enough detail to infer the distribution of each event across lots or to determine causality. The serious-event counts and the listed terms should not be treated as interchangeable summaries: one gives group counts of affected participants, while the terms identify reported event categories.
In general, safety counts are interpreted in the context of the number of participants monitored, the event definition, follow-up duration, and how events were assessed. The registry reports groups at risk and affected counts, but detailed timing, duration, severity, relatedness assessments, and event-level descriptions are not reported in the registry record. The counts alone also cannot establish whether rates differ meaningfully between lots. No formal comparative safety analysis is reported.
12. What the Result Does, and Does Not, Mean
The posted primary endpoint results describe neutralizing-antibody GMTs on Day 29 after a single vaccination in baseline-negative participants who met the per-protocol criteria. The estimates are reported separately for each of the three VLA1553 lots, with a 95% confidence interval for each. Their point estimates are on a similar scale, and the intervals overlap. These observations describe the posted data; they are not the result of a formal test of lot consistency.
The study’s stated objective was to demonstrate lot-to-lot consistency. However, a stated objective and descriptive estimates do not establish that a formal statistical criterion was met. The registry does not report an acceptable consistency margin, a prespecified decision rule, a between-lot contrast, or a formal test result. Without those details, the GMTs cannot determine whether the study formally demonstrated consistency under its protocol.
The endpoint is an antibody measure, not a direct clinical outcome. The registry results do not establish whether participants were protected from chikungunya infection, how long antibody responses persisted, or how the results relate to outcomes outside the study population. The primary analysis is restricted to baseline-negative participants in the per-protocol immunogenicity population and should not be generalized automatically to all randomized participants or other populations.
The safety information is also descriptive. The registry reports serious adverse event counts and zero deaths in each lot group, as well as several serious event terms. Those data do not establish causality or prove that rare events are absent. The record does not provide the detailed event-level context or comparative safety analysis that would support stronger conclusions.
Overall, the registry provides lot-specific day-29 antibody estimates and selected safety counts. It does not include enough reported statistical detail to verify a formal lot-consistency conclusion, assess all analysis decisions, or draw conclusions beyond the measured outcomes and populations.
13. Why This Trial Matters Statistically
Lot-to-lot consistency is a statistical question because a vaccine may be produced in separate lots, and researchers may need to assess whether measured responses are sufficiently alike under a prespecified standard. The comparison is not simply whether each lot has a measurable antibody response. It concerns the relationship among responses across lots and how much uncertainty surrounds that relationship.
This study is identified as a randomized, double-blinded Phase 3 trial with a parallel design, and its stated purpose was to assess three VLA1553 lots in healthy adults. It reports a defined primary immunogenicity endpoint and lot-specific GMT estimates with confidence intervals. These features give readers descriptive information about how the measured antibody responses compare across the three groups.
The registry record also illustrates why descriptive closeness should be distinguished from a formal consistency conclusion. A formal conclusion depends on the target comparison, an acceptable margin or other decision rule, and the uncertainty around the relevant contrast. The record reports group-level estimates and intervals but not those decision elements or a formal comparison result. Consequently, the posted values can inform a descriptive reading without independently establishing the stated study objective.
The use of a per-protocol immunogenicity population is another important statistical feature. The result applies to participants meeting that population definition, rather than automatically to every randomized participant. Reporting both the overall enrollment and lot-specific analysis counts helps distinguish the trial population from the endpoint population, although the registry does not report a full accounting of exclusions or missing measurements.
Finally, a study with several immune and safety outcomes raises questions about outcome prioritization, missing data, and multiplicity. The registry identifies a primary endpoint and lists secondary outcomes, but does not report the full analysis plan or multiplicity approach. Recognizing these limits helps readers separate what the posted estimates directly describe from the broader claims that would require additional statistical reporting.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The registry provides the three lot-specific GMT estimates and confidence intervals, but does not report a formal contrast among lots. It also does not report the consistency margin or decision rule needed to interpret a formal lot-consistency analysis. The descriptive estimates therefore cannot be used to verify whether the stated objective was met according to a prespecified statistical criterion.
Details of the analysis are limited. The record does not report the exact statistical model, data transformation, handling of assay values outside measurable ranges, or whether any adjusted analysis was performed. It lists 0 analyses. The registry also does not report a sample-size justification for the trial, so the planning illustration assumptions should not be taken as the protocol’s design rationale.
The primary endpoint uses a per-protocol population restricted to participants who tested negative for chikungunya virus antibodies at baseline. Although the record defines the per-protocol population in terms of major protocol deviations, it does not provide a full participant flow, detailed exclusion reasons, or the handling of missing endpoint measurements. The primary endpoint counts are not a complete substitute for that information.
Multiplicity procedures for the primary and secondary outcomes are not reported in the registry record. The record lists several additional immunogenicity and safety outcomes, but does not describe whether they were confirmatory, how their analyses were prioritized, or how multiple testing was addressed.
Safety reporting is also limited to selected summaries. Detailed event-level information, timing, relatedness, and a formal comparison among lots are not reported. The results concern the stated age range, healthy-adult population, per-protocol immunogenicity subgroup, assay, and Day 29 assessment; the registry record does not provide evidence for conclusions beyond those settings.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Study to Demonstrate Consistency of Three Lots of a Live-attenuated Chikungunya Virus Vaccine Candidate in Healthy Adults — NCT04786444.
- Registry record last updated 2023-09-28; status last verified 2023-09.
- Results first posted 2023-09-28.
- 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
NCT04786444 is a completed, randomized, double-blinded, parallel Phase 3 study of three lots of the live-attenuated chikungunya virus vaccine candidate VLA1553 in healthy adults aged 18 to 45 years. Overall enrollment was 409, and the study’s stated purpose was to demonstrate lot-to-lot consistency.
The primary endpoint was the Day 29 GMT of chikungunya virus-specific neutralizing antibodies measured by μPRNT among baseline-negative participants in the per-protocol immunogenicity population. The registry reports GMTs and 95% confidence intervals for each lot, along with serious adverse event counts and selected serious event terms.
The record does not report a formal between-lot analysis, consistency margin, decision rule, sample-size justification, missing-data method, or multiplicity procedure. The posted endpoint values therefore support a descriptive account of antibody responses but do not, on their own, verify a formal statistical conclusion about lot consistency.