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 Safety, Tolerability, and Immunogenicity of the COVID-19 Vaccine Candidates VBI-2902a and VBI-2905a (NCT04773665), a randomized phase 1 study. The primary outcome is Rate of Local Solicited Adverse Events After Each Study Vaccination.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT04773665 |
| Phase | Phase 1 |
| Condition | Covid19 |
| Allocation | Randomized |
| Design model | Sequential |
| Masking | Triple |
| Enrollment | 114 |
| Arms in the primary outcome | n/a |
| Lead sponsor | VBI Vaccines Inc. |
| Results posted | Yes |
2. Clinical Question
The study asked whether the investigational vaccine candidates VBI-2902a and VBI-2905a could be evaluated for safety, tolerability, and immunogenicity in healthy adults. Its primary endpoint concerned local solicited adverse events after vaccination; antibody responses were among the secondary outcomes. The trial had two portions with different vaccination histories and regimens, so their questions should be read separately rather than treated as one direct comparison.
Population
Healthy adults aged 18-54 were enrolled in the Phase 1a groups. Phase 1b participants aged 18-54 had previously received an authorized mRNA COVID-19 vaccine. The registry record describes the Phase 1b population as previously vaccinated, but does not report further eligibility details in the information available.
Intervention
Phase 1a evaluated VBI-2902a, which expresses the spike protein of the SARS-CoV-2 Wuhan isolate. The candidate was given with 5 μg of S protein and alum adjuvant, as either a one-dose or two-dose regimen. Phase 1b evaluated one dose of VBI-2905a, which expresses the spike protein of variant Beta, with 5 μg of S protein and alum adjuvant.
Comparator
Placebo was used in both portions. In Phase 1a, the groups included a one-dose VBI-2902a regimen followed by placebo, two VBI-2902a doses, and placebo at both scheduled administrations. In Phase 1b, VBI-2905a was compared with placebo at Day 1.
Primary question
The primary endpoint was the rate of local solicited adverse events through 7 days after each study vaccination, among participants who received a study vaccination. The record does not reduce this endpoint to one reported comparison or provide a single inferential result for it. Neutralizing-antibody and spike-protein-binding-antibody geometric mean titers were listed as secondary outcomes.
3. Trial Design
This was a Phase 1a/1b randomized, observer-blind, placebo-controlled study with a sequential model and triple masking, as recorded in the registry. The study was completed. Its enrollment was 114. The record gives a start date of 2021-03-15 and a primary completion date of 2022-11-14. It does not report which individuals or roles were included in the masking description.
Phase 1a examined VBI-2902a in three groups. Group G1 received VBI-2902a at 5 μg of S protein on Day 1 and placebo on Day 28. Group G2 received VBI-2902a at 5 μg on Days 1 and 28. Group G3 received placebo on Days 1 and 28. These groups were described as participants aged 18-54.
Phase 1b examined a one-dose regimen of VBI-2905a at 5 μg of S protein on Day 1, with a placebo group also assigned to Day 1. Both Phase 1b groups were described as participants aged 18-54 who had previously been vaccinated with an authorized mRNA COVID-19 vaccine. The two portions therefore involved distinct candidate vaccines and population histories. Their assignments are not a single head-to-head comparison of VBI-2902a with VBI-2905a.
The stated goals included safety, tolerability, and immunogenicity. The listed secondary outcomes were geometric mean titers of neutralizing antibody and spike-protein-binding antibody in serum for each trial portion. Although those outcomes appear in the registry, their numerical results and analyses are not reported in the registry record. Details of sequence generation, allocation concealment, and the operational conduct of masking are also 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 | Phase 1a, Group G1 | Phase 1a, Group G2 | Phase 1a, Group G3 | Phase 1b, Group G4 | Phase 1b, Group G5 |
|---|---|---|---|---|---|
| STARTED | 21 | 20 | 20 | 27 | 26 |
| COMPLETED | 19 | 19 | 19 | 24 | 26 |
| NOT COMPLETED | 2 | 1 | 1 | 3 | 0 |
Analysis population for the primary outcome, as defined in the registry: Safety Set: subjects who received a study vaccination.
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 | Phase 1a, Group G1 | Phase 1a, Group G2 | Phase 1a, Group G3 | Phase 1b, Group G4 | Phase 1b, Group G5 | Total |
|---|---|---|---|---|---|---|---|
| Participants analysed | 21 | 20 | 20 | 27 | 26 | 114 | |
| Age, Continuous | years | 31.8 (SD 9.37) | 32.9 (SD 9.45) | 30.8 (SD 9.03) | 36.3 (SD 11.03) | 36.6 (SD 9.87) | 33.68 (SD 9.77) |
| Age, Customized: 18 to 39 | Participants | 17 | 15 | 18 | 14 | 15 | 79 |
| Age, Customized: 40 to 55 | Participants | 4 | 5 | 2 | 13 | 11 | 35 |
| Sex: Female, Male: Female | Participants | 7 | 7 | 11 | 16 | 16 | 57 |
| Sex: Female, Male: Male | Participants | 14 | 13 | 9 | 11 | 10 | 57 |
| Race/Ethnicity, Customized: Race – Asian | Participants | 2 | 2 | 2 | 1 | 2 | 9 |
| Race/Ethnicity, Customized: Race – Black or African American | Participants | 0 | 0 | 2 | 0 | 0 | 2 |
| Race/Ethnicity, Customized: Race – First Nations | Participants | 0 | 0 | 0 | 0 | 0 | 0 |
| Race/Ethnicity, Customized: Race – Multiple | Participants | 1 | 0 | 1 | 1 | 3 | 6 |
| Race/Ethnicity, Customized: Race – White | Participants | 16 | 17 | 12 | 24 | 21 | 90 |
| Race/Ethnicity, Customized: Race – Other | Participants | 2 | 1 | 3 | 1 | 0 | 7 |
| Race/Ethnicity, Customized: Ethnicity – Hispanic or Latino | Participants | 1 | 1 | 1 | 1 | 0 | 4 |
| Race/Ethnicity, Customized: Ethnicity – Not Hispanic or Latino | Participants | 20 | 19 | 19 | 26 | 26 | 110 |
| Region of Enrollment: Canada | participants | 21 | 20 | 20 | 27 | 26 | 114 |
6. Primary Endpoint
The registry lists the primary outcome as Rate of Local Solicited Adverse Events After Each Study Vaccination, measured over Through 7 days after each study vaccination.
| Element | Registry entry |
|---|---|
| Result type | Count Of Participants |
| Measure of spread | not applicable |
| Unit | Participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint is the rate of local solicited adverse events after each study vaccination, assessed through 7 days after vaccination. It concerns events near the injection site that were actively solicited from participants during follow-up. The endpoint is expressed as participants with an event, and its stated population is the Safety Set: subjects who received a study vaccination.
The registry defines an adverse event broadly as an untoward medical occurrence after administration of a pharmaceutical product. The occurrence need not be considered causally related to the product. It can include an unfavorable or unintended sign, symptom, disease, or abnormal laboratory finding temporally associated with use. Thus, an adverse event is not automatically evidence that a vaccine caused the event. The endpoint’s local and solicited features narrow the specific question to actively collected events near the injection site within the stated follow-up window.
General: Solicited safety outcomes can make data collection more systematic because participants are asked about specified events during a defined period. Reporting participants with an event describes how many people experienced at least one qualifying event; it is not the same as counting every occurrence. Such a safety endpoint is relevant to early evaluation, while antibody titers address a different question about immune response.
The record does not report a single primary-endpoint comparison or a statistical analysis for the endpoint. The posted adverse-event summaries include serious and other event counts, but the registry record does not establish that those categories are the same as the primary local solicited endpoint. They should not be substituted for a primary-endpoint result.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry describes a small early-phase study organized into two portions, with different candidate vaccines, schedules, and vaccination histories. Phase 1a compared three VBI-2902a/placebo schedules in adults aged 18-54. Phase 1b evaluated a one-dose VBI-2905a regimen and placebo among previously mRNA-vaccinated adults in the same age range. Because these portions address different regimens and populations, a comparison across them would not isolate the effect of changing only the vaccine candidate.
The posted safety summaries report serious-event counts and other-event counts by group. For Phase 1a Group G1, 1 of 21 participants at risk was recorded with a serious event and 16 of 21 with another event. For G2, the corresponding counts were 0 of 20 and 17 of 20; for G3, 1 of 20 and 15 of 20. In Phase 1b Group G4, the counts were 0 of 27 and 27 of 27; for G5, they were 0 of 26 and 23 of 26. The record reports 0 deaths in each group. These are descriptive counts in the posted summaries, not estimates of a causal treatment effect.
The registry also lists Post-traumatic stress disorder at 5.0% and Myocardial infarction at 4.8% among the top serious terms. The record does not identify these terms as arm-specific comparisons in the information available. Their listed percentages therefore cannot be used to compare assigned groups or determine whether a treatment caused an event.
The primary endpoint concerns local solicited events through 7 days after each vaccination. The posted summaries are not identified as a single result for that endpoint, and the registry notes that the primary outcome has several categories or time points and was not reduced to one comparison. No primary-outcome analysis is listed. Likewise, neutralizing-antibody and spike-protein-binding-antibody geometric mean titers are listed as secondary outcomes, but no analyses are listed for them. The registry record therefore does not support a numerical interpretation of antibody response or a single primary-endpoint treatment contrast.
General: Counts describe observed participants and are most informative when read alongside their denominators, outcome definitions, and follow-up. Small groups can yield imprecise estimates, and differences in counts alone do not establish that groups differ beyond chance. A confidence interval, when reported, would convey the range of effects compatible with the data under the analysis assumptions; no such interval is reported for a primary comparison in the registry record.
The posted planning illustration uses a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect expressed as a fraction of the observed effect. It is a planning exercise based on an observed effect, not the trial's design justification or observed power. The registry record does not report the trial's own sample-size justification.
9. Statistical Methods Explained
Randomization means that assignment to the study groups is intended to use chance rather than participant or investigator choice. In general, this can reduce systematic differences between groups at assignment, but it does not ensure that every group will be identical, especially when groups are small. The registry labels this study randomized but does not report the randomization sequence method or allocation-concealment procedures.
The study is described as placebo-controlled and triple-masked. A placebo comparator helps distinguish observations in an assigned vaccine group from observations under the study's placebo condition. Masking is intended to limit the influence of knowing assignment on participant reporting, clinical assessment, or other study conduct. The registry does not specify which roles were masked, how masking was maintained, or whether it was assessed, so more detailed claims about those procedures are not warranted.
The sequential model and the Phase 1a/1b structure indicate that the registry presents the study in distinct portions. Phase 1a evaluates two VBI-2902a schedules and placebo; Phase 1b evaluates VBI-2905a and placebo in participants previously vaccinated with an authorized mRNA vaccine. General: when cohorts differ in vaccine history, candidate, or schedule, their results should not be treated as though they arose from one exchangeable randomized comparison. The record does not describe the operational rules for moving between portions or any decision criteria governing sequence.
What does a participant count measure?
The primary outcome is defined in terms of participants with an event. A participant count records whether people met the outcome definition; it does not necessarily count repeated episodes in the same person. The denominator matters because a count without the number at risk gives little context. The registry identifies the primary population as the Safety Set, defined as subjects who received a study vaccination. It does not report further details about exclusions from that set or how participants with incomplete follow-up were handled.
The posted adverse-event summaries distinguish serious events from other events and give counts at risk and affected by group. The record does not define the “other” category in the information available, nor does it identify those summaries as the primary local solicited outcome. General: outcome definitions should be checked before treating two event summaries as interchangeable. Local solicited events, serious adverse events, and broader event categories can represent different measures.
Why do outcome definitions and time windows matter?
The primary endpoint covers local events actively solicited through 7 days after each study vaccination. The time window determines which events qualify for that endpoint, while the solicitation procedure shapes what is collected. The endpoint is not equivalent to all events reported over the entire study. The record does not report the individual local-event categories, their separate results, or how repeated vaccinations were represented in a single analysis.
The registry lists antibody geometric mean titers as secondary outcomes. General: a geometric mean is often used for measurements that vary multiplicatively or are analyzed on a logarithmic scale. It summarizes the central level of measurements after accounting for that scale. A geometric mean titer alone would not describe the spread of individual responses; uncertainty measures and the analysis population would also help readers assess precision. Numerical titer results and analysis details are not reported in the registry record.
What can a statistical comparison establish?
General: an unadjusted comparison contrasts observed outcomes between groups without accounting for additional covariates. Its interpretation depends on the design, outcome definition, and assumptions behind the test or model. A confidence interval describes uncertainty around an estimated effect under those assumptions; it is not a guarantee that the true effect lies within the interval. A p-value addresses compatibility between data and a specified null model, not the probability that a treatment works or that the null hypothesis is true.
No primary analysis is listed in the registry, and the analysis count is 0. The record does not report a statistical test, model, effect estimate, confidence interval, or p-value for the primary endpoint. It is therefore not possible to describe an inferential method as having been used for that endpoint. The planned sample-size illustration is explicitly based on the observed effect, with two-sided significance level 0.05, equal allocation, and a normal approximation. It is not a report of observed power and is not the trial's sample-size justification.
How should group differences be approached?
General: raw counts can look different because of chance, different denominators, or variation in participant characteristics. Comparing event rates requires a clearly defined outcome and a suitable analysis; no new rates or contrasts should be inferred from counts without an explicitly reported analysis. Even a valid estimate can be imprecise, particularly when information is limited. The registry's descriptive safety counts can be read as recorded observations, but they do not by themselves establish a treatment effect.
Over-dispersion is a general issue for count outcomes when observed variability exceeds what a chosen count model expects. In that situation, standard errors from an overly restrictive model can be too small and intervals too narrow. This study's primary endpoint is specified as participants with an event, not as an event-frequency model, and the registry reports no model or dispersion assessment. Over-dispersion should therefore not be assumed to have been evaluated or to explain any result.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists several outcomes: a primary safety endpoint and secondary geometric mean titers for neutralizing antibody and spike-protein-binding antibody in both Phase 1a and Phase 1b. Multiple outcomes or comparisons can raise a multiplicity issue because examining more hypotheses can increase the chance of at least one apparently noteworthy result under a set of null hypotheses. General: prespecified testing hierarchies or adjustment procedures can address this issue, but their use depends on the study's analysis plan.
The statistical plan for multiplicity, including whether outcomes were tested in a hierarchy or adjusted for multiple comparisons, is not reported in the registry record. The record lists no analyses, so it does not provide inferential results that could be assessed for multiplicity. The presence of several listed outcomes does not establish that formal hypothesis tests were conducted.
The record defines a Safety Set as subjects who received a study vaccination. It does not report an intention-to-treat population, an immunogenicity analysis population, or the rules used to include participants in analyses. It also does not report the number of participants with missing outcome data, reasons for missingness, follow-up completeness for each endpoint, or any imputation or other missing-data method. No assumptions about missing observations can be made from the group counts alone.
General: missing data can affect interpretation when the chance of missingness is related to assignment, outcome, or participant characteristics. Analyses may address this through stated assumptions and sensitivity checks, but those methods need to be reported to evaluate their implications. Because such details are not reported in the registry record, the robustness of any outcome estimates to missing data cannot be assessed from this record.
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 |
|---|---|---|---|
| Phase 1a, Group G1 | 1 | 21 | 4.8% |
| Phase 1a, Group G2 | 0 | 20 | 0.0% |
| Phase 1a, Group G3 | 1 | 20 | 5.0% |
| Phase 1b, Group G4 | 0 | 27 | 0.0% |
| Phase 1b, Group G5 | 0 | 26 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Phase 1a, Group G1 | 0 of 21 |
| Phase 1a, Group G2 | 0 of 20 |
| Phase 1a, Group G3 | 0 of 20 |
| Phase 1b, Group G4 | 0 of 27 |
| Phase 1b, Group G5 | 0 of 26 |
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 |
|---|---|
| Phase 1a, Group G1 | 16 of 21 |
| Phase 1a, Group G2 | 17 of 20 |
| Phase 1a, Group G3 | 15 of 20 |
| Phase 1b, Group G4 | 27 of 27 |
| Phase 1b, Group G5 | 23 of 26 |
Most frequent serious adverse event terms
| Event term | Organ system | Phase 1a, Group G1 | Phase 1a, Group G2 | Phase 1a, Group G3 | Phase 1b, Group G4 | Phase 1b, Group G5 |
|---|---|---|---|---|---|---|
| Myocardial infarction | Cardiac disorders | 1 of 21 | 0 of 20 | 0 of 20 | 0 of 27 | 0 of 26 |
| Post-traumatic stress disorder | Psychiatric disorders | 0 of 21 | 0 of 20 | 1 of 20 | 0 of 27 | 0 of 26 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Phase 1a, Group G1 | Phase 1a, Group G2 | Phase 1a, Group G3 | Phase 1b, Group G4 | Phase 1b, Group G5 |
|---|---|---|---|---|---|---|
| COVID-19 | Infections and infestations | 5 of 21 | 5 of 20 | 2 of 20 | 20 of 27 | 16 of 26 |
| Vaccination site pain | General disorders | 10 of 21 | 7 of 20 | 9 of 20 | 8 of 27 | 12 of 26 |
| Post vaccination syndrome | Injury, poisoning and procedural complications | 3 of 21 | 5 of 20 | 6 of 20 | 3 of 27 | 4 of 26 |
| Headache | Nervous system disorders | 3 of 21 | 5 of 20 | 4 of 20 | 2 of 27 | 4 of 26 |
| Fatigue | General disorders | 3 of 21 | 3 of 20 | 5 of 20 | 1 of 27 | 3 of 26 |
| Oropharyngeal pain | Respiratory, thoracic and mediastinal disorders | 2 of 21 | 0 of 20 | 0 of 20 | 4 of 27 | 5 of 26 |
| Nausea | Gastrointestinal disorders | 1 of 21 | 3 of 20 | 1 of 20 | 3 of 27 | 1 of 26 |
| Chills | General disorders | 2 of 21 | 3 of 20 | 2 of 20 | 1 of 27 | 1 of 26 |
| Nasal congestion | Respiratory, thoracic and mediastinal disorders | 3 of 21 | 0 of 20 | 1 of 20 | 2 of 27 | 2 of 26 |
| Pyrexia | General disorders | 3 of 21 | 1 of 20 | 3 of 20 | 0 of 27 | 0 of 26 |
Serious events with the highest arm-level rate: post-traumatic stress disorder (5.0%), myocardial infarction (4.8%).
The safety summaries report the number at risk and the number affected by serious events and by other events in each group. In Phase 1a, G1 reports 1 serious-event participant among 21 at risk and 16 with another event among 21; G2 reports 0 among 20 and 17 among 20; G3 reports 1 among 20 and 15 among 20. In Phase 1b, G4 reports 0 among 27 and 27 among 27; G5 reports 0 among 26 and 23 among 26. Each group reports 0 deaths.
These are group-level counts, not evidence that an event was caused by a study vaccine. The registry's general adverse-event definition says that an event need not have a causal relationship with treatment. The record does not define the “other” event category in the information available, and these summaries should not be equated with the primary local solicited endpoint without a matching definition.
The record lists Post-traumatic stress disorder at 5.0% and Myocardial infarction at 4.8% among top serious terms. It does not clarify their group attribution or give a comparison associated with those percentages in the information available. They should be read as listed serious-event terms, not as a basis for comparing treatments. The registry record does not report further case-level details or a causal assessment for these terms.
12. What the Result Does, and Does Not, Mean
The registry record establishes that the trial was designed to examine safety, tolerability, and immunogenicity of two investigational vaccine candidates in separate Phase 1a and Phase 1b portions. It records randomized placebo-controlled groups and provides descriptive safety counts. It also identifies the intended primary endpoint and several antibody outcomes. Those features describe the study's questions and recorded observations; they do not, on their own, answer whether one regimen differs from another.
The listed counts show that serious-event counts were 1 in G1, 0 in G2, 1 in G3, 0 in G4, and 0 in G5; each group had 0 deaths. Counts for other events are also reported by group. The registry does not provide a primary-endpoint comparison, uncertainty interval, or statistical test. The reported serious-event counts should not be taken as proof of either a treatment-caused harm or an absence of harm.
The endpoint itself is limited to local solicited events through 7 days after each vaccination. It does not encompass every possible safety outcome or all follow-up. The available summaries do not establish which adverse-event categories correspond to that endpoint. The record also lists antibody geometric mean titers as secondary outcomes, but does not report their analyses or numerical results. No conclusion about antibody response can be drawn from the outcome names alone.
General: a study result is most interpretable when the outcome, population, comparison, effect estimate, and uncertainty are all specified. A descriptive count answers how many participants were recorded with an event in a group; it does not quantify a causal contrast. A non-significant result, if one were reported, would not by itself demonstrate equivalence, and no such result is listed in this record.
The trial's phase, group sizes, and reported safety data make the registry relevant as an early evaluation record, but they do not substitute for a complete statistical report. The protocol's sample-size justification, detailed analysis plan, missing-data handling, and inferential results are not reported in the registry record. The planning illustration is not observed power and should not be read as evidence that the study was sufficiently powered to detect a particular effect.
13. Why This Trial Matters Statistically
This study illustrates why trial structure matters when reading clinical data. Although both candidate vaccines were evaluated with placebo controls, Phase 1a and Phase 1b differed in candidate, schedule, and participant vaccination history. Phase 1b participants had previously received an authorized mRNA COVID-19 vaccine, whereas the Phase 1a descriptions do not state that history. The two portions therefore answer distinct questions and should not be collapsed into one comparison.
It also distinguishes safety measurement from immunogenicity measurement. The primary endpoint concerns actively solicited local events during a specified post-vaccination window. The listed secondary outcomes concern serum antibody titers. These outcomes have different meanings, data structures, and interpretations; a safety count cannot stand in for an antibody response, and an antibody outcome does not by itself describe safety.
Statistically, the record is a reminder to separate descriptive summaries from inferential evidence. Group counts and denominators convey observed safety information, while the absence of a reported comparison means that the strength and precision of any between-group contrast cannot be assessed. A planning calculation based on an observed effect is also distinct from the original design justification and from observed power.
The registry record is useful for identifying the intended endpoint, populations, schedules, and posted safety observations. At the same time, the missing analysis details limit what can be inferred. The record does not report outcome-specific inferential analyses, multiplicity procedures, missing-data methods, or a sample-size justification. Recognizing these gaps is part of responsible statistical interpretation, not a reason to replace them with assumptions.
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 record does not report a single primary-endpoint comparison. It notes that the primary outcome has several categories or time points and was not reduced to one comparison. Although the endpoint is defined as local solicited adverse events through 7 days after each vaccination, the posted event summaries are not explicitly identified as that endpoint. This limits direct interpretation of the summaries against the stated primary question.
The record lists 7 outcome measures and 0 analyses. It names secondary antibody outcomes but does not report their results, estimates of uncertainty, or analysis populations. It also does not report a statistical analysis plan, method for handling multiple outcomes, missing-data methods, or a trial-specific sample-size justification. The planning assumptions do not fill those gaps.
The group descriptions give planned assignments, while the posted safety summaries give numbers at risk that differ between some groups. The registry record does not explain the reasons for those differences or report participant flow and endpoint-specific follow-up. It also does not provide detailed eligibility criteria beyond the age range and prior mRNA vaccination history described for Phase 1b.
Further limitations include the lack of reported randomization and allocation-concealment procedures, detail about which roles were masked, and case-level information or group attribution for the top serious terms. The available summaries are descriptive and do not establish causation. The separate phases, schedules, and vaccination histories also limit direct comparisons across all five groups. These considerations restrict the conclusions that can be drawn from the registry record alone.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Safety, Tolerability, and Immunogenicity of the COVID-19 Vaccine Candidates VBI-2902a and VBI-2905a — NCT04773665.
- Registry record last updated 2024-05-17; status last verified 2024-05.
- Results first posted 2024-05-17.
- 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
NCT04773665 is a completed Phase 1a/1b randomized, observer-blind, placebo-controlled study with triple masking and a sequential model. The registry lists enrollment of 114 and describes VBI-2902a regimens in Phase 1a and a one-dose VBI-2905a regimen in Phase 1b. Phase 1b participants had previously received an authorized mRNA COVID-19 vaccine.
The primary endpoint was local solicited adverse events through 7 days after each study vaccination, among participants who received a study vaccination. Secondary outcomes included serum geometric mean titers of neutralizing antibody and spike-protein-binding antibody. The registry posts descriptive safety counts, including 0 deaths in each group, but lists no analyses. It does not report a single primary-outcome comparison, antibody analyses, a trial-specific sample-size justification, or details of missing-data handling.