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 Open-label, Randomized Study in a Pediatric Population in a JEV (Japanese Encephalitis Virus)-Endemic Country (NCT01296360), a randomized phase 3 study. The primary outcome is SCRs (Seroconversion Rate) as Defined by Percentage of Subjects With Plaque Reduction Neutralization Test Titers of>1:10 at 1 Month After the Booster Dose.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01296360 |
| Phase | Phase 3 |
| Condition | Japanese Encephalitis |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 300 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Valneva Austria GmbH |
| Results posted | Yes |
2. Clinical Question
Population
Children in a Japanese encephalitis virus-endemic country who had received IXIARO in study IC51-323. The brief summary describes eligible children as aged >9 months to <17 years and 7 months. The primary immunogenicity population is described as all randomized subjects.
Intervention
The study concerns primary vaccination with IXIARO and subsequent follow-up, with or without a booster dose. The registry lists a booster group and a non-booster group for safety outcomes. Age-defined intervention descriptions list IXIARO doses of 0.25 ml intramuscularly for >14 months to <2 years and 0.5 ml intramuscularly for >3 years to <18 years.
Comparator
The study title and safety outcomes distinguish participants with and without a booster. The posted primary endpoint results, however, are organized by age group: >14 months to <2 years and >3 years to <18 years. The registry record does not report a primary endpoint comparison between booster and non-booster groups.
Primary question
What proportion of participants had a plaque reduction neutralization test titer >1:10 one month after the booster dose? This seroconversion rate is reported separately for the two age-defined groups. The registry also lists longer-term antibody and safety outcomes, but posted numerical results are not available for those outcomes.
The clinical question combines an immune-response outcome with a longer-term safety and immunity objective. The primary endpoint is a threshold-based measure: it classifies each participant according to whether the measured neutralizing antibody titer is above the specified level. That gives a proportion rather than an average antibody concentration.
The distinction between the stated study objective and the posted primary results matters. The title describes evaluation with or without a booster, while the primary results are reported for age-defined groups and both are 100.0%. The registry record does not report a primary endpoint estimate contrasting the booster group with the non-booster group. The primary figures therefore answer the recorded age-group summaries, not a direct estimate of the booster’s effect compared with no booster.
3. Trial Design
This was a randomized, open-label, parallel-group Phase 3 study. The registry lists 300 participants enrolled and the study status as completed. The recorded study start is 2010-12, and primary completion is recorded as 2011-11. Masking is listed as none, so the study is described as open-label rather than blinded.
The study concerns children previously vaccinated with IXIARO in study IC51-323. The brief summary describes the target age range as >9 months to <17 years and 7 months. The intervention descriptions list two age-defined groups and IXIARO doses: 0.25 ml intramuscularly for the >14 months to <2 years group, and 0.5 ml intramuscularly for the >3 years to <18 years group. The difference between those age descriptions and the broader eligibility description is present in the registry record; further explanation is not reported in the registry record.
The title and safety outcomes refer to booster and non-booster groups. The primary immunogenicity endpoint is timed one month after a booster dose, while the safety outcomes include follow-up after the first vaccination and after the booster. The registry record does not report the detailed allocation sequence, concealment procedures, the precise visit schedule, or how participants were assigned to the age-defined categories in the posted primary results.
The primary analysis population is described as the intent-to-treat population, defined as all subjects randomized, for immunogenicity analyses. The primary results list 81 participants in the >14 months to <2 years group and 67 in the >3 years to <18 years group. The registry record does not explain how those group counts relate to the 300 enrolled participants, nor does it report the number included in each booster-status group for the primary endpoint.
Eight secondary outcomes are listed in addition to the primary outcome. They cover antibody titers and threshold attainment at one month after a booster, antibody outcomes at Months 12, 24 and 36 after the first vaccination, and adverse events over several follow-up periods. Numerical posted results for those secondary outcomes are not reported in the registry record.
4. Participant Flow and Accounting
The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.
Overall Study
| Stage | Booster Group | Non-Booster Group |
|---|---|---|
| STARTED | 150 | 150 |
| Visit 2 (Month 12) | 148 | 149 |
| Visit 2a (Month 13) | 148 | 0 |
| COMPLETED | 144 | 142 |
| NOT COMPLETED | 6 | 8 |
Analysis population for the primary outcome, as defined in the registry: Intent-to-treat Population: primary analysis population for the immunogenicity analyses; defined as all subjects randomized
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 Population: subjects who entered into the study and were randomized
| Characteristic | Unit | Booster Group | Non-Booster Group | Total |
|---|---|---|---|---|
| Participants analysed | 150 | 150 | 300 | |
| Age, Continuous | years | 5.23 (SD 5.084) | 5.36 (SD 5.135) | 5.30 (SD 5.101) |
| Sex: Female, Male: Female | Participants | 72 | 79 | 151 |
| Sex: Female, Male: Male | Participants | 78 | 71 | 149 |
6. Primary Endpoint
The registry lists the primary outcome as SCRs (Seroconversion Rate) as Defined by Percentage of Subjects With Plaque Reduction Neutralization Test Titers of>1:10 at 1 Month After the Booster Dose, measured over 1 month post booster.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | 95% Confidence Interval |
| Unit | percentage of subjects |
| Endpoint classification | Binary Endpoint |
The primary endpoint is the seroconversion rate, defined as the percentage of subjects with a plaque reduction neutralization test titer >1:10 at one month after the booster dose. A plaque reduction neutralization test (PRNT) measures neutralizing antibody activity in a laboratory assay. The endpoint converts each participant’s measured titer into a binary outcome: the titer either exceeds the specified threshold or it does not. The reported rate is the proportion meeting that criterion.
A threshold-based endpoint is useful because it gives a direct summary of how many participants crossed a prespecified antibody level, rather than describing only an average titer. It is easier to interpret as a proportion, but it also discards information about how far each person’s result lies above or below the threshold. Participants with different titers can count equally if both are on the same side of the cutoff.
The registry reports a 100.0% rate in each age-defined group: 81 participants in the >14 months to <2 years group and 67 in the >3 years to <18 years group. The respective 95% confidence intervals are 95.5% to 100.0% and 94.6% to 100.0%. These estimates describe the recorded endpoint at the specified time after a booster. The registry record does not report individual titers, the assay’s full operating characteristics, or numerical primary endpoint results for a booster-versus-no-booster contrast.
7. Results Posted in the Registry
- >3 Years - <18 Years: 100.0% (67/67) versus 100.0% (81/81) on control; risk difference 0.0 percentage points (95% CI 0.0 to 0.0), risk ratio 1.00 (1.00–1.00); unadjusted two-proportion z-test p = n/a.
Risk difference: >3 Years - <18 Years
95% CI: 0.0 to 0.0 percentage points
Recalculated from the posted summary statistics
8. Statistical Interpretation
For the recorded primary endpoint, both age-defined groups had a reported seroconversion rate of 100.0% one month after the booster dose. The registry lists 81 participants in the >14 months to <2 years group and 67 in the >3 years to <18 years group. The 95% confidence intervals are 95.5% to 100.0% and 94.6% to 100.0%, respectively. These results indicate that every participant in each listed analysis group met the endpoint threshold according to the posted percentages. The registry does not provide the underlying individual-level results.
The two point estimates are identical, but identical observed proportions do not establish that the underlying response rates are identical. Confidence intervals express uncertainty around estimates, and the intervals extend below 100.0%. They show that the observed rate should not be read as proof that the population rate is exactly 100.0%. The posted results do not report a formal test comparing the age-defined groups, and no such test should be inferred from the matching percentages.
The record includes a comparison estimate of a risk difference of 0.0, with bounds of 0.0 to 0.0. It does not explain the method used for that comparison, and it is not presented as a booster-versus-no-booster comparison. The primary endpoint results themselves are arranged by age group. Therefore, the comparison entry does not supply evidence about the effect of receiving a booster relative to not receiving one.
The study’s title describes long-term immunity and safety with or without a booster, and the listed secondary outcomes include antibody measurements and adverse events at later times. However, numerical results for those secondary outcomes are not reported in the registry record. The primary result alone cannot describe persistence of antibody responses at Months 12, 24 or 36, nor can it establish the comparative safety profile over the stated follow-up periods.
Safety summaries list 7 serious adverse events among 150 participants in the booster group and 3 among 150 in the non-booster group. These are descriptive event counts in the registry record. Without details such as event-level timing, attribution, severity classifications beyond the serious-event category, or a reported statistical comparison, the counts do not by themselves establish that one group had greater or lesser risk. The record also lists other adverse-event counts of 99 among 150 and 100 among 150, but the detailed definition of that category is not reported in the registry record.
The main statistical reading is consequently narrow: the posted data show high observed threshold attainment at one month after booster, with finite uncertainty intervals, in two age-defined groups. They do not provide a posted estimate of the booster’s comparative effect, detailed results for the planned longer-term endpoints, or a basis for broader conclusions beyond the recorded outcomes and analysis groups.
9. Statistical Methods Explained
The endpoint is binary at the participant level: each person either has a PRNT titer >1:10 at the specified visit or does not. The registry reports the percentage meeting that criterion. This is a proportion outcome, not a continuous measure such as the geometric mean titer. The two forms answer different questions: a proportion describes threshold attainment, while a geometric mean summarizes antibody levels on a transformed scale. The record lists both types of outcomes, but posted numerical results are available only for the primary proportion endpoint.
What does a confidence interval convey?
A confidence interval describes uncertainty in an estimated population value under the assumptions of the interval procedure. It is not a range containing a fixed fraction of individual participants’ outcomes, and it does not mean that the true value is equally likely to be anywhere within its limits. In repeated use of a valid procedure, intervals constructed in the same way would cover the target value at the stated rate. The registry gives 95% confidence intervals for the primary percentages.
Both observed percentages are 100.0%, while the lower confidence limits are below 100.0%. This is important: observing no participants below the threshold in the listed groups does not eliminate uncertainty about the underlying response rate. The upper limit reaches the maximum possible percentage, while the lower limit reflects uncertainty arising from the finite group sizes and the interval method. The exact interval method is not reported in the registry record.
How should the age-group comparison be read?
The displayed primary results are separated by age group, and each group has an observed value of 100.0%. The registry also records a risk difference of 0.0 with bounds of 0.0 to 0.0. A risk difference is a subtraction of two proportions, expressed on the percentage-point scale when the proportions are expressed as percentages. The posted comparison is not identified as a booster-versus-no-booster contrast, and the method underlying its bounds is not reported in the registry record. It should not be treated as a formal equivalence result or as proof that the populations have identical response rates.
When all observed participants meet a binary threshold, standard comparison procedures can behave differently depending on the chosen estimator and interval method. Some methods can yield boundary estimates or intervals with little apparent width. A zero-width reported range should therefore be interpreted in the context of the method and comparison definition. Neither is described in the registry record for this comparison.
Why is over-dispersion relevant?
General statistical explanation: for a binary endpoint, a simple binomial model assumes that participants’ outcomes are independent and that each participant in a group has the same underlying probability of meeting the threshold. Real data can depart from that model if participants differ in important ways or outcomes cluster. Such extra variation is called over-dispersion. If it is present and not accommodated, uncertainty can be understated. The registry record does not report whether over-dispersion was assessed or whether an alternative model was used.
For continuous outcomes such as antibody titers, analyses can involve transformation, geometric means, or models of repeated measurements. Those methods require information about the distribution, handling of values below assay limits, and within-person correlation across visits. The registry lists geometric mean titers at several follow-up times as secondary outcomes, but the statistical methods and numerical results for them are not reported in the registry record.
What is not described about the analysis?
The record identifies the primary immunogenicity population as the intent-to-treat population, defined as all randomized subjects. It does not report the detailed endpoint analysis method, interval construction, handling of missing endpoint measurements, or whether participants were analyzed according to assigned group regardless of booster receipt. The primary age-group counts are 81 and 67, whereas overall enrollment is 300; a reconciliation of these numbers is not reported in the registry record.
The record lists no posted analyses in addition to the descriptive primary results. A formal hypothesis test, model, adjustment method, or analysis plan is not reported in the registry record. The reported comparison estimate alone does not reveal those procedures. Consequently, the explanation of the percentages and confidence intervals can describe what the statistics mean generally, but it cannot identify the exact computational approach used by the study sponsor.
For safety, the record gives counts and denominators for serious and other adverse events in groups of 150. Event counts are not interchangeable with participant risks unless the reporting unit is clear; the record labels the figures as numbers of affected subjects for the listed groups. It does not provide the event-level data, time-to-first-event analysis, exposure-adjusted rates, or a comparative inferential method. Those omissions limit any statistical interpretation of differences in safety counts.
General statistical explanation: a randomized design can support causal comparisons when the comparison is specified and analysis follows the randomized assignment, with appropriate handling of missing data and deviations. Randomization alone does not make every descriptive subgroup comparison a causal estimate. In this record, the primary posted results are age-defined summaries, while the booster and non-booster labels appear in safety summaries. The direct numerical primary contrast by booster status is not reported in the registry record.
10. Confidence Intervals and Precision
The primary estimates are 100.0% in both age-defined groups. The 95% confidence interval for the >14 months to <2 years group is 95.5% to 100.0%, based on 81 participants. For the >3 years to <18 years group, the interval is 94.6% to 100.0%, based on 67 participants. These intervals show uncertainty even though the observed proportions are at the upper boundary of the possible range.
Because the outcome is a percentage, the limits are also expressed as percentages. The lower limit indicates that values below the observed 100.0% remain compatible with the data under the interval procedure. The upper limit cannot exceed 100.0%, the endpoint’s natural maximum. The two intervals overlap substantially, but overlap is not itself a formal test of whether the groups differ. A group comparison requires a specified estimand and an appropriate method; the registry record does not report those details for the primary endpoint.
Precision depends on the amount of information in the analysis and on the statistical method used. The primary group sizes are smaller than the total enrollment of 300, and the registry does not explain the relationship between those counts. It also does not report endpoint missingness, the number with evaluable samples at the visit, or the interval construction method. These details would help assess how the confidence limits were obtained and which population they represent.
The comparison entry gives a risk difference of 0.0, with bounds of 0.0 to 0.0. Since the record does not state the comparison’s interval method or clearly connect this entry to booster status, those bounds should be read cautiously. They do not replace the separate confidence intervals for the age-defined primary results, and they should not be interpreted as evidence of exact equality between groups.
11. Multiplicity, Missing Data and Analysis Populations
The registry lists one primary outcome and eight secondary outcomes. The secondary outcomes span antibody threshold attainment, geometric mean titers, longer-term immune measures, and several adverse-event categories across different follow-up periods. Considering multiple outcomes and time points can increase the chance of observing an apparently notable result by chance if many statistical tests are performed. A prespecified multiplicity strategy can address that issue, for example by controlling the overall error rate or defining a hierarchy of outcomes. Whether such a strategy was used is not reported in the registry record.
The registry record does not report numerical results for the secondary outcomes or inferential analyses for them. It also does not state whether any interim analyses were planned or conducted, how the primary endpoint analysis was specified in advance, or whether adjustments were made for multiple comparisons. No assumptions about these procedures can be made from the completed status or the list of outcomes.
The primary immunogenicity population is described as all subjects randomized. That definition identifies the intended population, but the record does not report the number of missing measurements at the primary visit, the method used to handle missing endpoint data, or whether all randomized participants were included in the posted age-group results. The relationship between the reported analysis counts of 81 and 67 and the total enrollment of 300 is not explained.
The study also has safety summaries for booster and non-booster groups. The registry reports 150 participants at risk in each group for the listed serious-event and other adverse-event counts. It does not report a formal safety analysis population definition, exposure duration, missing follow-up, or comparative analysis method. Since adverse events can occur over time and may recur, the choice between counting participants, events, or time at risk can affect interpretation; the record’s detailed analytic approach is not reported in the registry record.
Without these details, the posted primary percentages can be described as recorded, but the broader analysis strategy cannot be reconstructed. A reader should distinguish the listed outcome definitions from evidence that a particular missing-data or multiplicity method was used.
12. 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 |
|---|---|---|---|
| Booster Group | 7 | 150 | 4.7% |
| Non-Booster Group | 3 | 150 | 2.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Booster Group | 99 of 150 |
| Non-Booster Group | 100 of 150 |
Most frequent serious adverse event terms
| Event term | Organ system | Booster Group | Non-Booster Group |
|---|---|---|---|
| Abscess | Infections and infestations | 1 of 150 | 0 of 150 |
| Amoebic dysentery | Infections and infestations | 1 of 150 | 0 of 150 |
| Bronchopneumonia | Infections and infestations | 1 of 150 | 0 of 150 |
| Dengue fever | Infections and infestations | 1 of 150 | 0 of 150 |
| Gastroenteritis | Infections and infestations | 1 of 150 | 0 of 150 |
| Urinary tract infection | Infections and infestations | 1 of 150 | 0 of 150 |
| Concussion | Injury, poisoning and procedural complications | 0 of 150 | 1 of 150 |
| Injury | Injury, poisoning and procedural complications | 0 of 150 | 1 of 150 |
| Pneumothorax traumatic | Injury, poisoning and procedural complications | 0 of 150 | 1 of 150 |
| Paralysis | Nervous system disorders | 0 of 150 | 1 of 150 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Booster Group | Non-Booster Group |
|---|---|---|---|
| Upper respiratory tract infection | Infections and infestations | 37 of 150 | 34 of 150 |
| Rhinitis | Infections and infestations | 17 of 150 | 16 of 150 |
| Nasopharyngitis | Infections and infestations | 16 of 150 | 15 of 150 |
| Varicella | Infections and infestations | 9 of 150 | 14 of 150 |
| Pyrexia | General disorders | 10 of 150 | 8 of 150 |
| Gastroenteritis | Infections and infestations | 7 of 150 | 8 of 150 |
| Bronchitis | Infections and infestations | 6 of 150 | 8 of 150 |
| Impetigo | Infections and infestations | 10 of 150 | 4 of 150 |
| Viral infection | Infections and infestations | 9 of 150 | 5 of 150 |
| Fever | General disorders | 12 of 150 | 0 of 150 |
Serious events with the highest arm-level rate: abscess (0.7%), amoebic dysentery (0.7%), bronchopneumonia (0.7%), dengue fever (0.7%), gastroenteritis (0.7%).
The registry lists 7 participants with serious adverse events among 150 in the booster group and 3 among 150 in the non-booster group. These are descriptive counts, with 150 listed as at risk in each group. The record does not report a formal comparison, a confidence interval for the difference, or an adjusted analysis. The counts alone do not establish whether the groups differ in underlying risk.
The registry also records 99 affected participants in an other adverse-event category among 150 in the booster group and 100 among 150 in the non-booster group. The precise definition of this category is not reported in the registry record. Serious-event terms listed at 0.7% each are abscess, amoebic dysentery, bronchopneumonia, dengue fever, gastroenteritis, and urinary tract infection. The record does not provide enough detail to determine the timing, duration, relatedness, or group assignment for each listed term.
The listed secondary outcomes specify several distinct safety windows, including after the first vaccination, after the booster, and solicited events for up to 7 days following the booster. Numerical results for those separate windows are not reported in the registry record. The summarized group counts should therefore not be taken as a complete account of all safety findings or as a direct comparison of event rates over equal observed time.
13. What the Result Does, and Does Not, Mean
The posted primary data show that the recorded seroconversion rate was 100.0% in each of two age-defined groups one month after the booster dose. The 95% confidence intervals extend down to 95.5% for the >14 months to <2 years group and 94.6% for the >3 years to <18 years group. This describes a high observed rate of crossing the specified PRNT threshold in the analyzed groups, while retaining uncertainty about the population values.
The result does not establish that every child in the broader eligible population would meet the threshold, nor does it describe the magnitude of antibody response above the threshold. A threshold endpoint treats all results above the cutoff alike. The registry does not report individual titers or the distribution of antibody levels.
It also does not establish the effect of a booster compared with no booster. The title and secondary outcomes refer to participants with and without a booster, but the posted primary endpoint values are presented by age group. Numerical primary results for a booster-versus-no-booster comparison are not reported in the registry record. The listed risk difference of 0.0 is not identified as that contrast.
The one-month outcome does not answer whether antibody levels persisted at Months 12, 24 or 36. Those time points appear among the secondary outcomes, but their numerical results are not reported in the registry record. Nor does the primary immune endpoint address adverse events. The safety counts are descriptive, and a detailed comparative safety analysis is not reported.
Finally, these registry results should be interpreted in light of the incomplete reporting of analysis details. The record does not report the exact interval method, endpoint missingness, or the relationship between the primary analysis counts and total enrollment. These limitations do not change the stated percentages, but they constrain what can be concluded from them.
14. Why This Trial Matters Statistically
This study illustrates how the organization of results shapes the question a reader can answer. The study title emphasizes long-term immunity and comparison with or without a booster, but the posted primary outcome is a one-month threshold measure organized by age group. Those data are informative about the recorded immune response in the listed groups, but they are not a direct estimate of the booster’s comparative effect.
It also demonstrates why a point estimate of 100.0% should be read alongside its confidence interval. An observed rate at the maximum possible value can look definitive, yet the interval limits indicate uncertainty about the underlying population response. Reporting both the estimate and interval helps distinguish the observed sample from the broader population to which researchers may wish to generalize.
The record also provides an example of the limits of registry outcome listings. Several longer-term antibody and safety outcomes are described, but numerical results are not reported in the registry record. An outcome’s presence in a study record does not itself provide evidence about its result. Similarly, overall enrollment does not explain the analysis population without a clear account of eligibility, follow-up, and endpoint availability.
For biostatistical interpretation, the central lesson is to align the claim with the actual estimand and analysis population. Age-stratified percentages, booster-status safety counts, and a study objective about long-term immunity are distinct pieces of information. They should not be substituted for one another. Clear reporting of comparisons, analysis methods, missing data, and follow-up results would allow readers to evaluate the intended clinical question more fully.
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.
- Participant counts were reconstructed from posted percentages and arm sizes, so small rounding differences are possible.
The primary results are reported for age-defined groups, while the study title and safety outcomes describe booster and non-booster groups. The registry record does not report a primary endpoint comparison by booster status. This limits interpretation of the main objective as a direct comparative estimate.
The age ranges are not fully aligned across record descriptions. The brief summary describes children aged >9 months to <17 years and 7 months, while the intervention descriptions list >14 months to <2 years and >3 years to <18 years. The record does not explain these differences or the absence of ages between the listed groups. It also does not explain how the primary groups of 81 and 67 relate to total enrollment of 300.
Numerical results for the eight secondary outcomes are not reported in the registry record. That includes the listed longer-term immune outcomes and the distinct adverse-event follow-up periods. Consequently, the posted primary result cannot characterize durability or provide a comprehensive account of safety over follow-up.
Several analysis details are also not reported: the exact confidence interval method, handling of missing primary measurements, the detailed analysis plan, any multiplicity approach, or interim analyses. The record does not give individual-level results, event timing, or a full definition of the other adverse-event category. These omissions limit verification and make it difficult to distinguish the effects of analysis choices from the observed summaries.
Finally, the study is described as open-label with no masking. That design feature is relevant to interpretation, particularly for subjective or medically attended adverse-event reporting. The record does not provide further details about outcome assessment procedures that would clarify how open-label status may have affected reporting.
16. Related Tutorials
17. Related Statistical Calculators
18. Sources
- ClinicalTrials.gov: Open-label, Randomized Study in a Pediatric Population in a JEV (Japanese Encephalitis Virus)-Endemic Country — NCT01296360.
- Registry record last updated 2014-12-19; status last verified 2014-12.
- Results first posted 2014-12-19.
- 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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19. Record Summary
This completed, randomized, open-label, parallel-group Phase 3 study enrolled 300 participants and examined long-term immunity and safety after primary IXIARO vaccination, with or without a booster. The primary endpoint was the percentage with a PRNT titer >1:10 one month after the booster dose.
The posted primary results report 100.0% in both age-defined groups: 81 participants in the >14 months to <2 years group, with a 95% confidence interval of 95.5% to 100.0%, and 67 participants in the >3 years to <18 years group, with a 95% confidence interval of 94.6% to 100.0%.
Safety summaries list 7 serious adverse events among 150 participants in the booster group and 3 among 150 in the non-booster group. Numerical results for the listed secondary immune and safety outcomes, a primary booster-versus-no-booster comparison, and several analysis details are not reported in the registry record.