MRKAd5 HIV-1 Gag Vaccine (V520) in Subjects With Chronic Hepatitis C (V520-022) (COMPLETED): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for MRKAd5 HIV-1 Gag Vaccine (V520) in Subjects With Chronic Hepatitis C (V520-022) (COMPLETED) (NCT00857311), a randomized phase 1 study. The primary outcome is Number of Participants With Vaccine-related Clinical (Systemic and Injection-site), and Laboratory Adverse Events (AE).

2. Clinical Question

The trial asked whether a three-dose regimen of MRKAd5 HIV-1 Gag vaccine (V520) could be assessed for safety and tolerability in subjects with chronic hepatitis C. Its primary endpoint counted participants with vaccine-related clinical or laboratory adverse events. The official title also describes immunogenicity as an objective, and the registry lists an immune-response outcome, but the posted results do not report an analysis of that outcome.

3. Trial Design

This was a randomized, double-blind, parallel-group Phase 1 study, with an additional open-label control arm described in its official title. The registry marks the trial as completed and reports enrollment of 17. The enrolled safety groups with posted counts are the MRKAd5 HIV-1 Gag vaccine 1x10^9 vp/dose group and the placebo group. Their reported at-risk counts are 9 and 8, respectively.

The vaccine regimen in the 1x10^9 vp/dose arm consisted of administration on Day 1, Week 4, and Week 26. The placebo arm followed the same schedule. The record also describes a 1x10^10 vp/dose vaccine arm and an open-label tetanus and diphtheria toxoids adsorbed arm. It states that no participants were enrolled in either of those groups, following notification that enrollment would be halted because of recruitment challenges. The notice was dated 30-Aug-2005, and the halt was to take effect as of 01-Oct-2005.

The registry lists the start as 2004-05 and primary completion as 2006-01. It does not report the randomization procedure, the allocation ratio, the method used to maintain masking, or further operational details about the open-label arm. The record identifies Merck Sharp & Dohme LLC as sponsor. Although the official title includes immunogenicity, the posted outcomes do not include a reported analysis of immune response. The registry describes 3 outcome measures and 0 analyses.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

Reasons for not completing this period:

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.

6. Primary Endpoint

The registry lists the primary outcome as Number of Participants With Vaccine-related Clinical (Systemic and Injection-site), and Laboratory Adverse Events (AE), measured over up to Week 78 (52 weeks after boost injection) for systemic AEs, 29 days after any dose for laboratory AEs, and 5 days after any dose for injection-site AEs.

The primary endpoint is the number of participants with vaccine-related clinical and laboratory adverse events. Clinical events include systemic and injection-site events. The registry defines vaccine-related events as those the investigator judged possibly, probably, or definitely related to vaccine administration. Systemic and laboratory events are described as unfavorable and unintended changes in the body’s structure, function, or chemistry; injection-site events include swelling, redness, pain, or tenderness.

The endpoint captures whether participants experienced an event, rather than measuring an event’s severity on a continuous scale. In general, counting participants with an event is one way to summarize safety and tolerability: it records how many people were affected during the specified observation periods. It does not by itself describe the full clinical course, severity, duration, or recurrence of events. Those details require separate reporting.

The registry specifies different observation windows: systemic adverse events were followed up to Week 78, described as 52 weeks after the boost injection; laboratory adverse events were followed for 29 days after any dose; and injection-site adverse events were followed for 5 days after any dose. These windows matter when interpreting an event count because each type of event is observed over a distinct period. The posted record does not give a single formal comparison for this primary endpoint, and its skip note says the outcome has several categories or time points and was not reduced to one comparison.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry presents this as a randomized, double-blind, parallel-group Phase 1 trial, with an additional open-label control arm described in the title. These design features describe how groups were intended to be compared; they do not replace the need for reported outcome analyses. The record gives group-level adverse-event counts for the 1x10^9 vp/dose vaccine and placebo arms, but reports 0 analyses. It does not report the statistical methods used for a primary comparison.

What an event count represents

The primary outcome is a participant count: it concerns how many participants experienced vaccine-related adverse events, rather than the total number of event episodes. A participant-based count can be useful for a safety summary because it indicates how many people had an event during the defined observation period. It may not capture repeated events in the same person, timing, duration, intensity, or clinical course. In general, event counts and event rates answer different questions, so the outcome definition and denominator need to be clear when interpreting a result.

The record reports at-risk and affected counts for serious and other adverse events in the two groups. It does not report confidence intervals, p-values, or an effect estimate for these counts. Without an inferential analysis, the observed group summaries do not establish whether an apparent difference is compatible with random variation or represents a stable difference in the populations under study. General statistical interpretation of a difference would ordinarily consider its magnitude and uncertainty together, while recognizing the trial’s size and design.

Attribution and observation windows

Vaccine-relatedness was determined by the investigator as possibly, probably, or definitely related to vaccine administration. This is an attribution rule, not a randomized comparison. In general, attribution may require judgment about whether an event is related to an intervention; it does not by itself prove causation. The registry does not report how investigators applied this judgment across individual events or whether an independent review was used.

Systemic adverse events were monitored up to Week 78, specified as 52 weeks after the boost injection. Laboratory events were monitored for 29 days after any dose, and injection-site events for 5 days after any dose. These observation periods define what can be captured for each category. A count from one period should not be treated as if it arose from the same duration of observation as a count from another. The record does not provide a single analysis that combines or contrasts these categories and time windows.

Randomization and masking

Randomization is intended, in general, to reduce systematic differences between assigned groups, while masking can reduce the influence of treatment knowledge on care and assessment. The registry identifies randomized allocation and double masking for the main study, but does not describe the sequence-generation method, concealment procedures, who was masked, or how masking was maintained. The separate open-label arm was not masked by definition, and the record says no participants were enrolled in that group. These design labels alone do not show whether implementation was successful.

Planning calculations and power

The registry’s planning illustration is described as a calculation from the observed effect, not as the trial’s original design justification. Its stated assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is a stated fraction of the observed effect. For time-to-event outcomes, the described planning quantity is total events; for other outcomes, it is participants per arm. These are hypothetical planning quantities, not observed enrollment requirements, and they are not observed power. The registry does not report the trial’s own sample-size justification, so the planning illustration should not be read as evidence about the original design process.

In general, power is a design-stage probability tied to an assumed effect, variability, sample size, and testing approach. It is not a measure of how convincing an observed result is. A calculation based on the effect observed in a completed trial is especially dependent on that estimate and does not create a new confirmatory analysis. No numerical planning result or formal test result is reported in the registry record for the primary endpoint.

Multiplicity and model choice

The endpoint includes several adverse-event categories and observation periods. In general, when multiple outcomes, time points, or comparisons are examined, a statistical plan may specify which result is primary and how multiplicity is handled. The registry does not report such a plan or a multiplicity adjustment. The skip note states that the primary outcome has several categories or time points and was not reduced to one comparison. No regression model, covariate adjustment, or other analysis model is reported. It is therefore not possible to determine from the registry whether any adjusted or confirmatory analyses were planned or performed.

10. Multiplicity, Missing Data and Analysis Populations

The primary endpoint spans systemic, injection-site, and laboratory adverse events, with different observation periods for each. The registry’s skip note says the primary outcome has several categories or time points and was not reduced to one comparison. No single formal comparison is reported. The record does not state how multiple categories, time points, or any other outcomes were prioritized, nor does it describe a multiplicity strategy. Any planned control of false-positive findings is not reported in the registry record.

Missing-data handling is also not reported in the registry record. The posted counts include at-risk numbers for the serious and other adverse-event summaries, but the record does not describe whether participants had complete follow-up for every event category, how incomplete observations were handled, or whether any participants were excluded from particular endpoint assessments. No analysis population definition—such as an intention-to-treat or safety population—is reported. The group counts alone do not establish which analysis population was used.

The registry reports 0 analyses. A statistical analysis plan, interim analyses, and any procedures for addressing deviations from the planned analysis are not reported in the registry record. This limits what can be said about prespecification, multiplicity, and the treatment of missing observations. It also means that the posted descriptive adverse-event figures should not be mistaken for a complete account of every planned analysis or endpoint.

In general, missing-data methods matter because the interpretation of a count depends on who was observed and over what period. Multiplicity methods matter because repeated testing across outcomes or time points can affect how evidence is interpreted. Neither issue can be resolved from the reported counts alone.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: hepatitis c (12.5%), alcohol abuse (12.5%), multiple fractures (11.1%), uterine leiomyoma (11.1%).

The registry lists serious adverse events for 2 of 9 participants at risk in the 1x10^9 vp/dose vaccine group and 2 of 8 at risk in the placebo group. It lists other adverse events for 9 of 9 at risk in the vaccine group and 6 of 8 at risk in the placebo group. These are group-level safety counts; the record does not report a formal statistical comparison or confidence intervals for them. Deaths are not reported in the registry record.

The listed serious-event terms include Hepatitis C and Alcohol abuse at 12.5% each, and Multiple fractures and Uterine leiomyoma at 11.1% each. The registry does not report denominators or further context for these term-level percentages in the registry record, so they should be read as the record’s listed percentages rather than as a direct comparison between groups. The term list alone does not establish whether an event was judged vaccine-related.

Seriousness and relatedness are distinct classifications. The primary endpoint’s vaccine-related designation depended on investigator judgment, while the adverse-event summary separately identifies serious and other events. The counts do not by themselves establish causation, severity beyond the seriousness classification, timing, recurrence, or comparative risk. The small group counts also warrant a descriptive rather than conclusive reading.

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

The record documents a randomized, double-blind, parallel-group Phase 1 study of MRKAd5 HIV-1 Gag vaccine in subjects with chronic hepatitis C, with posted safety counts for a 1x10^9 vp/dose group and placebo. It also records the primary endpoint definition, event-attribution criteria, and distinct follow-up periods. These details make clear what the safety question was intended to capture and how the recorded counts should be understood.

The posted information does not establish a formal statistical answer to the primary question. The registry reports 0 analyses and does not provide an inferential comparison, a confidence interval, or a p-value for the primary endpoint. The counts can describe the participants recorded as having serious and other adverse events in the two groups, but they do not show the precision of a between-group effect estimate. Nor do they establish whether any observed difference is attributable to the intervention.

The record does not report an analysis of immune response, despite immunogenicity being named in the official title and an immune-response outcome appearing among the listed outcomes. It also does not report enrollment in the higher-dose vaccine or open-label tetanus and diphtheria toxoids adsorbed arms. Findings from the enrolled vaccine and placebo groups therefore cannot be extended to those unrepresented groups based on this record.

In general, a safety count is one part of an assessment, not a standalone causal conclusion. Interpretation also depends on event definitions, duration of observation, completeness of follow-up, and the analysis plan. Those details are not all reported. The record supports describing the trial’s design and its posted counts; it does not support a definitive claim about comparative safety, immunogenicity, or treatment effect.

13. Why This Trial Matters Statistically

This trial is statistically informative as an example of the difference between a registered endpoint and a reported analysis. The primary outcome is defined as a count of participants with vaccine-related clinical and laboratory adverse events, and the record specifies what qualifies as vaccine-related. Yet the registry reports 0 analyses and indicates that the endpoint’s several categories or time points were not reduced to one comparison. A clearly stated endpoint does not, by itself, provide an interpretable treatment-effect estimate.

The record also illustrates why denominators and follow-up windows matter in safety reporting. Serious and other adverse-event counts are given for the two groups with posted results, while the primary endpoint includes categories observed over different periods. Those summaries can describe recorded experience, but without a formal comparison and uncertainty estimates they cannot answer how precisely the groups differ.

The planned higher-dose vaccine and open-label control arms had no enrolled participants according to the registry. This makes the distinction between intended design and actual enrollment important: the official title describes an additional control arm, while the posted group counts pertain to the vaccine and placebo groups. The record also names immunogenicity as an objective but does not report its analysis.

In general, registry records are most useful when their design, outcome definitions, analysis populations, missing-data handling, and statistical results can be considered together. This record shows how incomplete analysis reporting constrains interpretation, even when the study status is completed and descriptive safety counts are available.

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 principal limitation for statistical interpretation is that the registry reports 0 analyses. It gives descriptive adverse-event counts but no formal primary-endpoint comparison, confidence interval, or p-value. The skip note explicitly says the primary outcome has several categories or time points and was not reduced to one comparison. Consequently, a single treatment-effect estimate and its precision cannot be inferred from the record.

Enrollment was 17, and the posted at-risk counts for the two safety groups are 9 and 8. The registry says no participants were enrolled in the 1x10^10 vp/dose vaccine group or the open-label tetanus and diphtheria toxoids adsorbed group. The record therefore does not provide safety results for those planned arms. It also does not report an immune-response analysis, despite listing an immune-response outcome.

Important analysis details are not reported in the registry record, including the randomization method, allocation ratio, analysis populations, missing-data handling, statistical analysis plan, interim analyses, multiplicity strategy, and sample-size justification. Follow-up completeness and the denominators for the listed serious-event term percentages are also not reported in the registry record. These omissions limit assessment of precision, prespecification, and the relationship between the listed summaries and the full primary endpoint.

The study is identified as Phase 1 and concerns subjects with chronic hepatitis C. The registry does not report information sufficient to assess how well the enrolled participants represent other populations. The descriptive counts should therefore be understood within the recorded groups and should not be generalized beyond what the record documents.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: MRKAd5 HIV-1 Gag Vaccine (V520) in Subjects With Chronic Hepatitis C (V520-022) (COMPLETED) — NCT00857311.
• Registry record last updated 2015-08-25; status last verified 2015-08.
• Results first posted 2011-07-07.
• 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.

18. Record Summary

This completed Phase 1 randomized, double-blind, parallel-group study assessed MRKAd5 HIV-1 Gag vaccine in subjects with chronic hepatitis C. The registry reports enrollment of 17 and safety counts for the 1x10^9 vp/dose vaccine and placebo groups. No participants were enrolled in the planned 1x10^10 vp/dose vaccine or open-label tetanus and diphtheria toxoids adsorbed groups.

The primary endpoint counted participants with vaccine-related clinical and laboratory adverse events over specified follow-up periods. The registry reports descriptive serious and other adverse-event counts, but 0 analyses and no formal primary-endpoint comparison. An immune-response outcome is listed, but its analysis is not reported. The record does not report the statistical analysis plan, missing-data methods, or sample-size justification.