Efficacy of B7A BSIgG Against E. Coli Strain B7A Challenge: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Efficacy of B7A BSIgG Against E. Coli Strain B7A Challenge (NCT03040687), a randomized phase 1 study. The primary outcome is Safety of Serum Derived Bovine Immunoglobulins (BSIgG).

2. Clinical Question

The central statistical question is therefore a safety comparison across the three immunoglobulin groups in a controlled challenge setting. The registry reports counts of participants with serious and other adverse events, but it does not provide an adjusted comparison, confidence intervals, or an analysis of efficacy against diarrhea. The safety counts can describe what was recorded during follow-up; they do not by themselves establish whether event patterns differ beyond chance or whether one product offers protection against disease.

3. Trial Design

This was a Phase 1, randomized, quadruple-masked, parallel-group clinical trial. The registry lists 60 enrolled participants, describes them as healthy volunteers, and marks the study as completed. The recorded study start is 2017-01 and primary completion is 2017-04. The sponsor is Johns Hopkins Bloomberg School of Public Health.

All three registered groups were described as receiving a BSIgG product and the CS6-expressing ETEC challenge strain B7A. The Anti-CS6 group received anti-CS6 BSIgG; the Anti-whole Cell B7A group received anti-whole cell B7A BSIgG; and the control immunoglobulin group received negative-control, nonhyperimmune BSIgG. The registry identifies the products and lots, but does not report dose, schedule, route details beyond oral administration in the study summary, or the timing of challenge relative to product administration.

Random allocation is intended, in general, to make treatment groups comparable on average with respect to both measured and unmeasured baseline factors. Masking can reduce the influence of expectations on participant reporting, clinical assessment, or other trial procedures. The registry does not report the allocation sequence, concealment procedures, or which roles were masked, so those implementation details cannot be assessed. A parallel design means participants are assigned to a group rather than described as crossing between treatment groups.

The registered primary outcome concerns safety over 28 days: the number of participants with adverse events in the hyperimmune-product groups compared with the nonhyperimmune group. The study summary additionally states an aim to estimate protective efficacy against moderate-severe diarrhea after challenge. The available registry results do not include an efficacy estimate or an analysis of diarrhea outcomes. Eligibility criteria, baseline characteristics, adherence, and participant flow by group 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.

Before assignment: Study specific screening occurred prior to enrollment. Eighty-two subjects signed study specific consent forms. Nineteen subjects screened failed. Three subjects were randomized but did not receive BSIgG.

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 Safety of Serum Derived Bovine Immunoglobulins (BSIgG), measured over 28 days.

The primary outcome is the number of participants with adverse events in groups receiving B7A- and CS6-hyperimmune BSIgG, compared with the group receiving nonhyperimmune product. The recorded unit is participants, and the timeframe is 28 days. The registry’s adverse-event summary separates serious adverse events from other adverse events and lists group counts for each category.

Counting participants with an event is a binary-outcome approach: each participant is classified according to whether the specified event occurred during the stated period. A count communicates how many participants were recorded as affected in a group. It does not, by itself, indicate the event’s severity, duration, cause, or whether one participant experienced multiple events. Those details require separate reporting.

A safety endpoint is relevant in an early-phase study because the study evaluates tolerability as well as a possible protective effect. The registry identifies this as the primary outcome, but does not report a single inferential comparison or a confidence interval for the group contrast. Its note that the primary outcome has several categories or time points and is not reduced to one comparison further limits interpretation of a single summary number. The precise definitions of adverse events, ascertainment procedures, and handling of events extending beyond the stated timeframe are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a count of participants with an event represent?

A binary endpoint records whether each participant did or did not meet a defined event criterion during a specified period. The registry reports participant counts for adverse-event categories over 28 days. Such counts are useful for a direct description of how many participants were recorded with events in each group. They do not count every separate event when one participant can experience more than one event; the registry’s unit is participants, not event episodes.

For a rigorous comparison, the event definition and the method of ascertainment need to be consistent across groups. It also matters whether all participants were followed for the same period, how events were classified, and how incomplete follow-up was treated. Those operational details are not reported in the registry record. As a result, the counts can be read descriptively, but the available information does not establish how fully or uniformly events were collected.

Why is uncertainty important?

An observed count is a sample result, not a direct measurement of the underlying event probability in every similar population. General statistical inference uses an estimate of uncertainty to indicate how much the result could vary across comparable trials. A confidence interval is one common way to express the range of effect estimates compatible with the data and the analysis assumptions. A point estimate without an interval can give an incomplete impression, particularly when group sizes are limited or events are uncommon.

No confidence intervals, p-values, or adjusted effect estimates are reported for the adverse-event comparisons in the registry results. Therefore, the counts do not establish whether an apparent difference between groups is compatible with random variation or represents a reproducible contrast. The absence of a reported inferential result is not the same as a finding of no difference.

Why can sparse serious-event data be difficult to interpret?

When few or no serious events are observed, standard statistical estimates may be imprecise or may require methods designed for sparse data. Zero observed events do not mean that the true event risk is zero. They indicate only that none were recorded in the listed group during the recorded follow-up. The amount of uncertainty depends on the study size, follow-up, completeness, and analytic approach. The registry gives the counts and participants at risk but does not report an interval estimate or a model for these data.

More generally, binary outcomes are often compared using a difference in event probabilities, a ratio of probabilities, or another model-based contrast. These measures answer related but distinct questions. The registry does not report which contrast, if any, was used for a formal safety comparison. No new contrasts can be inferred from the displayed counts without conducting a separate analysis, and no recalculated result is reported.

What do the design labels contribute?

Randomization can reduce systematic differences between groups at assignment, while masking can reduce bias related to expectations or knowledge of treatment. These are general design benefits, not guarantees against bias. The registry identifies the trial as randomized and quadruple-masked, but does not describe sequence generation, allocation concealment, the identities of masked roles, or whether masking was maintained. The parallel-group structure assigns participants to one group rather than describing repeated treatment periods within each participant.

The trial has three registered groups: two hyperimmune-product groups and a nonhyperimmune control group. A comparison of each product with control would involve separate contrasts. General statistical practice requires attention to multiplicity when several comparisons or outcomes are examined, because repeated testing can increase the chance of at least one apparently unusual result. The registry does not report whether a multiplicity adjustment or a prespecified hierarchy was used.

How should planning illustrations be distinguished from trial evidence?

The planning assumptions described in the registry refer to an illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The assumed effect to detect is a stated fraction of the observed effect. Such planning outputs are conditional illustrations, not evidence about the trial’s actual design or operating characteristics. In particular, a sample-size illustration is not observed power and does not establish that the trial could reliably detect a safety or efficacy effect.

The registered trial itself has three groups, while the illustration’s assumptions describe a two-arm comparison. The illustration therefore should not be mistaken for the allocation structure of the trial. The registry does not report the trial’s own sample-size justification, power target, interim analyses, or a full statistical analysis plan. These details are not reported in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists two outcome measures, but the available information identifies the primary safety outcome and does not give a complete set of outcome definitions and analyses. The record notes that the primary outcome has several categories or time points and is not reduced to one comparison. This means a single overall effect estimate cannot be recovered from the reported information. Details of any prespecified outcome hierarchy, multiplicity adjustment, or selection among time points are not reported in the registry record.

When several endpoints, time points, or group contrasts are considered, multiplicity can increase the chance of a seemingly notable result arising by chance. General approaches include prespecifying a primary contrast, adjusting inference for multiple comparisons, or treating additional analyses as exploratory. The registry does not state which approach was used. There are no analysis results listed for the trial, and no p-values or confidence intervals are available for assessing multiplicity or precision.

Missing-data methods also matter: participants without complete follow-up may be excluded, classified under a defined rule, or handled using a statistical model. Each choice depends on why data are missing and on the outcome structure. The registry does not report the amount or pattern of missing data, the analysis population, exclusions, or how missing outcome observations were handled. Participant disposition by group and adherence information are not reported in the registry record.

Without these details, the event counts should be treated as descriptive registry results rather than a complete inferential analysis. The absence of reported methods does not demonstrate that a particular method was or was not used; it means that the method cannot be evaluated from the registry record.

11. Safety Results

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

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent non-serious adverse event terms

The serious-adverse-event summary lists 20 participants at risk in each of the three groups and 0 participants with serious adverse events in each group. Deaths are also recorded as 0 for every group. These entries describe what the registry records during the safety follow-up; they do not establish that serious events could not occur or that the products have identical safety profiles.

The same summary lists other adverse events in 19 participants in the Anti-CS6 group, 17 in the Anti-whole Cell B7A group, and 20 in the control immunoglobulin group. These are participant counts, not counts of all event episodes. The registry does not provide the event terms, severity breakdown, duration, relatedness, or timing for these other events. The list of top serious-event terms is empty.

A zero serious-event count can be reassuring as a description of the observed follow-up, but it remains limited by the number of participants, duration, event ascertainment, and completeness of reporting. No comparative statistical analysis or uncertainty interval is reported. The counts therefore should not be interpreted as proof of no risk, a demonstration of equivalence, or an estimate of a causal treatment effect.

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

The results support a narrow descriptive statement: during the reported 28-day timeframe, the registry records no serious adverse events and no deaths in any listed group, while recording other adverse events among participants in all three groups. The study was conducted in healthy volunteers in a challenge-trial setting, and its primary registered outcome concerns safety. These data are relevant to describing events observed in this study population under the recorded conditions.

They do not establish that the products prevent ETEC disease. Although the study summary describes estimating protective efficacy against moderate-severe diarrhea following challenge, the efficacy outcome results and a statistical comparison are not reported in the available registry record. The safety counts cannot substitute for diarrhea outcomes or an estimate of protection.

The counts also do not prove that the groups have the same safety profile. A formal comparison would need a defined contrast and an assessment of uncertainty, alongside details of outcome ascertainment and missing data. No such inferential results are reported. Nor can the counts alone show whether an event was caused by the product, the challenge, or another factor.

The result should therefore be read within its scope: a completed Phase 1 randomized, quadruple-masked, parallel study in healthy volunteers, with adverse-event counts reported for 28 days. The registry record does not report enough information to make broader claims about other populations, longer follow-up, efficacy, or comparative safety beyond the observed descriptive counts.

13. Why This Trial Matters Statistically

This trial is statistically informative as an example of the difference between a study objective and the results that are available for interpretation. The study summary includes both a safety aim and an efficacy aim, while the registered primary outcome is the number of participants with adverse events. The registry provides descriptive safety counts but no efficacy analysis result. Separating those aims prevents safety data from being misread as evidence about protection against diarrhea.

The design also highlights the value of randomized, masked comparisons in a controlled challenge setting. In general, randomization helps limit systematic baseline differences, and masking can reduce some forms of measurement or reporting bias. These features strengthen the design in principle, but they cannot replace reporting of the analysis, uncertainty, participant flow, and outcome definitions. Those details are not reported in the registry record.

Another statistical lesson is that zero serious events are not equivalent to zero risk. Counts describe the observed sample; inferential estimates are needed to convey uncertainty about underlying event rates. The same principle applies to the observed other-adverse-event counts: descriptive differences are not, by themselves, evidence of a reliable group effect.

Finally, the record notes a planning illustration based on the observed effect, using two-arm assumptions, while the registered study has three groups. This distinction matters because planning scenarios are not descriptions of the trial’s design and are not observed power. Clear separation of design assumptions, observed counts, and inferential conclusions is essential when interpreting early-phase clinical research.

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 provide efficacy results for moderate-severe diarrhea or another clinical outcome after B7A challenge. It therefore does not support an estimate of protective efficacy. The primary safety outcome is described as involving several categories or time points, but the available record does not reduce it to a single comparison or report an inferential analysis.

Safety reporting is limited to participant counts for serious and other adverse events, participants at risk, and deaths. Event terms, severity of other events, duration, timing, relatedness to product or challenge, and ascertainment procedures are not reported. The record also does not report missingness, follow-up completeness, participant flow, adherence, or analysis populations. These omissions constrain both the completeness of the descriptive results and the assessment of bias.

Although the design is listed as randomized and quadruple-masked, allocation procedures and the roles included in masking are not reported in the registry record. Baseline characteristics and eligibility details are also not available in the listed details, limiting assessment of group comparability and the population to which results might apply.

The study is identified as Phase 1 and includes healthy volunteers, so the results should not be generalized automatically to other populations or settings. The registry does not report the trial’s sample-size justification, full statistical analysis plan, interim analyses, or multiplicity procedures. The planning illustration described in the record uses two-arm assumptions and should not be treated as a description of the three-group trial or as observed power.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Efficacy of B7A BSIgG Against E. Coli Strain B7A Challenge — NCT03040687.
• Registry record last updated 2019-06-14; status last verified 2019-03.
• Results first posted 2019-06-14.
• 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

NCT03040687 is a completed, randomized, quadruple-masked, parallel Phase 1 study sponsored by Johns Hopkins Bloomberg School of Public Health. The registry lists 60 enrolled healthy volunteers, a start of 2017-01, and primary completion in 2017-04. Three groups received anti-CS6 BSIgG, anti-whole cell B7A BSIgG, or nonhyperimmune control BSIgG, with the CS6-expressing ETEC strain B7A challenge described in each group.

The primary registered outcome is the number of participants with adverse events over 28 days. The record lists 0 serious adverse events and 0 deaths in each group, and other adverse events in 19, 17, and 20 participants across the Anti-CS6, Anti-whole Cell B7A, and control groups, respectively. Efficacy results, inferential comparisons, and details needed to assess missing data and analysis methods are not reported in the registry record.