Evaluation of the Safety and Immune Responses of the Towne Strain of CMV in Seronegative Women: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Evaluation of the Safety and Immune Responses of the Towne Strain of CMV in Seronegative Women (NCT00201448), a randomized phase 2, phase 3 study. The primary outcome is Participants With Adverse Events.

2. Clinical Question

The study addressed vaccine safety and immune responses in women who were seronegative for CMV. Its stated context was the possibility that women could encounter CMV through children attending daycare centers, and the concern that infection during pregnancy can affect a child. Those statements describe the rationale in the study summary; they do not establish that the posted one-year outcome measures pregnancy-related infection or infant outcomes.

The registry identifies participants with adverse events as the primary outcome. It does not post a separate immune-response result among the two outcome measures, and it lists no secondary outcomes posted. The available primary result is therefore a safety count, not a direct estimate of vaccine-induced immunity, prevention of CMV infection, or effects on children.

The registry enrollment is 82, while the brief summary describes 180 women as the number to be vaccinated. The record does not explain the difference between those figures. It also lists the study status as terminated, without reporting the reason for termination. The posted outcome counts should be read in this context: they describe the registry’s reported endpoint results, but the record does not establish why the study ended or how complete follow-up was.

3. Trial Design

The registry describes a randomized, double-blind, parallel-group phase II–III study of Towne CMV vaccine and hepatitis A vaccine. Participants were assigned to one of the two vaccine groups. The registry lists 42 participants in the hepatitis A group and 40 in the Towne CMV vaccine group for the primary outcome. The total registry enrollment is 82.

The Towne vaccine arm description specifies 3000 pfu/subject. The hepatitis A arm is labeled as the placebo group, although the named intervention is hepatitis A vaccine. The study summary likewise says women would be given either cytomegalovirus vaccine or hepatitis A vaccine. The record does not provide further details about administration schedules, dose timing, randomization sequence generation, allocation concealment, or procedures used to maintain masking.

The brief summary describes blood collection before vaccination and collection of urine, saliva, and blood after vaccination every 1–6 months for up to 3 years. It also describes gathering information about reactions to vaccination, asking family members to provide urine and saliva samples, and testing children born to vaccinated women for CMV infection. These are descriptions of the intended study activities in the summary; the registry does not provide results for those activities in the posted outcome data.

The primary outcome is participants with adverse events, with a timeframe of one year. The outcome population is stated as per protocol and randomized. The record does not explain whether the reported counts combine those populations, how participants were classified, or how withdrawal and incomplete follow-up were handled. It also does not report the reason for termination, actual follow-up duration by participant, or whether the planned follow-up activities were completed.

The brief summary describes 180 women as the number to be vaccinated, whereas the registry enrollment is 82. These are distinct registry statements, and the record does not reconcile them. The actual outcome group counts are the figures attached to the posted primary result; the brief-summary figure should not be treated as the number analyzed for that endpoint.

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

Analysis population for the primary outcome, as defined in the registry: per protocol and 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.

6. Primary Endpoint

The registry lists the primary outcome as Participants With Adverse Events, measured over One year.

The primary endpoint is titled Participants With Adverse Events. It measures a count of participants, rather than a count of separate events, during the stated one-year timeframe. For the registry’s primary result, the hepatitis A group has a reported value of 0 among 42 participants, and the Towne CMV vaccine group has a reported value of 0 among 40 participants.

Counting participants affected is useful for a safety comparison because it describes how many people in each group experienced the outcome, rather than allowing someone with multiple events to contribute repeatedly to the participant count. A count alone does not describe the type, severity, timing, duration, or clinical importance of events. The registry’s primary outcome title is broad, and the record does not give a fuller definition of which events qualified, how they were collected, or whether all adverse events or a specified subset were included.

The one-year timeframe also matters when interpreting the count. The study summary describes follow-up activities extending for up to 3 years, but that does not change the stated timeframe for this primary endpoint. The record does not explain how the one-year assessment was handled for participants with incomplete observation.

Adverse-event outcomes are used in vaccine studies to describe safety observations during a defined period. They do not, by themselves, measure immune response or prevention of CMV infection. Those outcomes are not represented by the posted primary result, and no secondary outcomes are posted in the registry record.

7. Results Posted in the Registry

• Towne CMV Vaccine: 0.0% (0/40) versus 0.0% (0/42) on control; risk difference 0.0 percentage points (95% CI 0.0 to 0.0); unadjusted two-proportion z-test p = n/a.

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies this as a randomized, double-blind, parallel-group trial. In a randomized study, assignment to groups is intended to reduce systematic differences between groups at the start of the comparison. Double masking is intended to limit the influence of knowledge of assignment on participant experience, care, and outcome assessment. These are general purposes of the design labels; the registry does not describe the exact randomization or masking procedures used in this trial.

The primary endpoint is a count of participants with adverse events. A participant count differs from an event count: one participant is counted as affected if the endpoint definition is met, even if that person has more than one event. General statistical interpretation depends on a clear endpoint definition and consistent observation across groups. The registry does not provide the detailed definition or event-collection rules for this endpoint.

For the primary outcome, the registry reports 0 of 42 participants in the hepatitis A group and 0 of 40 in the Towne CMV vaccine group. It reports a risk difference of 0.0. In general, a risk difference compares the observed proportions with an outcome between groups by expressing their difference on the probability scale. A value of 0.0 indicates no observed difference in the reported proportions. The risk difference is not a relative measure and does not express how many events each participant experienced.

The registry reports confidence limits of 0.0 and 0.0 for that risk difference. In general, a confidence interval describes uncertainty around an estimate under the assumptions of its statistical method. Its interpretation depends on how the interval was calculated, the data included, and the analysis assumptions. The registry does not describe the method used for these limits. Since no analysis results are listed, no test statistic or p-value is available to explain the comparison further.

Zero observed outcomes require careful interpretation. General methods for binary outcomes use the number of participants with an event and the number observed in each group. When event counts are zero, information about the event probability is limited by the amount and completeness of observation. A reported estimate of no observed difference does not prove that the underlying probabilities are equal. Here, the posted confidence limits are both 0.0, but the record gives no calculation details with which to assess that interval’s behavior for zero counts.

The stated analysis population is per protocol and randomized. In general, an intention-to-treat analysis retains participants according to randomized assignment, while a per-protocol analysis applies criteria related to following the study regimen or protocol. The registry wording mentions both, but does not specify whether results were calculated separately or jointly, which participants were included, or what protocol adherence criteria were applied. It is therefore not possible to label the posted count as a clearly defined intention-to-treat or per-protocol estimate.

The record lists zero analyses. That means no analysis entries are posted in the registry, not that the primary outcome count is absent: the endpoint result and group comparison are reported separately. The record does not state whether the reported comparison was adjusted for any covariates, whether there were interim analyses, or what prespecified statistical analysis plan was used. Those details are not reported in the registry record.

A planning illustration based on an observed effect is conceptually different from an analysis of trial results. The described planning assumptions use a two-sided significance level of 0.05, equal allocation between groups, and a normal approximation, with the effect to detect defined as a fraction of the observed effect. Such an illustration is not observed power and is not the trial’s own design justification. The trial-specific sample-size justification is not reported in the registry record. The registry does not report the resulting planning sample counts in the registry record for this interpretation.

General considerations about over-dispersion are relevant when outcomes are counts of events and the variability exceeds what a simple count model assumes. The primary endpoint is a count of affected participants, with a binary status for each participant, rather than a reported number of recurrent events per person. The registry provides no participant-level event counts or model details, so there is no basis to assess over-dispersion for this endpoint.

Finally, the result is bounded by the stated one-year timeframe and the population included in the analysis. General interpretation of any trial estimate depends on whether participants were observed consistently, how missing measurements were handled, and whether the analysis population corresponds to the question of interest. The registry does not report follow-up completeness, missing outcome handling, or detailed analysis-population definitions. These omissions limit independent evaluation of the reported estimate.

10. Confidence Intervals and Precision

The registry reports a risk difference of 0.0, with confidence limits of 0.0 and 0.0. The two group outcome counts are zero in both groups: 0 among 42 participants in the hepatitis A group and 0 among 40 participants in the Towne CMV vaccine group. The numerical estimate therefore shows no observed difference in the posted counts.

In general, precision concerns how much uncertainty surrounds an estimate. A confidence interval is commonly used to express that uncertainty, conditional on the analysis method and its assumptions. A narrower interval is often interpreted as greater precision, but that interpretation depends on an appropriate interval calculation and adequate reporting of the method. The registry gives no method for the reported limits, so their construction cannot be evaluated from the record.

The reported limits are both exactly 0.0. This should not be taken as proof that the underlying risks are known without uncertainty. In general, observing no events does not establish that the event probability is zero; the amount of information depends on the number of participants observed and the completeness and duration of follow-up. The registry does not report missing outcome counts or participant-level follow-up details for this endpoint.

The record also does not report a p-value, an analysis specification, or separate estimates for the per-protocol and randomized populations. It is not possible to use the posted limits to infer those missing details. The confidence limits should be quoted as registry-reported, while recognizing that the available information is insufficient to independently assess their precision or method.

11. Multiplicity, Missing Data and Analysis Populations

The registry lists two outcome measures but no secondary outcomes posted, and it lists zero analyses. The posted primary outcome is participants with adverse events. The record does not identify a hierarchy of outcomes, explain whether multiple comparisons were planned, or report a multiplicity adjustment. With no secondary outcome results or analysis entries, the registry does not support conclusions about how multiple statistical tests were handled.

Missing-data handling is not reported in the registry record. The record does not state how many participants had incomplete one-year adverse-event information, whether follow-up differed between groups, how withdrawals were treated, or whether any imputation or other method was used. These details matter because an outcome count describes observed participants, while incomplete observation can affect what the count represents.

The primary population is described as per protocol and randomized. The registry does not clarify whether that phrase means two separate analysis populations, a combined definition, or another approach. It does not report eligibility criteria for those analyses, protocol deviations, exclusions after randomization, or group-specific analysis populations beyond the posted group counts.

The brief summary describes sample collection and follow-up activities for up to 3 years, whereas the primary adverse-event endpoint timeframe is one year. The record does not explain how the planned longer follow-up related to this endpoint or whether outcome collection was complete. The reason the study was terminated is also not reported. These omissions do not change the posted counts, but they constrain assessment of completeness, analysis choices, and the scope of the results.

12. 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 0% reporting threshold.

The registry’s serious adverse-event entries show 0 affected participants among 42 at risk in the hepatitis A group and 0 affected participants among 40 at risk in the Towne CMV vaccine group. The other adverse-event entries also show 0 affected participants in both groups. These are the reported counts for the categories listed in the safety information.

The record lists no serious adverse-event terms. An empty list of terms means that no terms are listed in the registry entry; it does not provide event descriptions or further context. Death counts are not reported in the registry record. The primary endpoint is titled Participants With Adverse Events, and the record does not fully define how it relates to the serious and other adverse-event categories.

Zero reported affected participants is not equivalent to evidence that no adverse event of any kind could occur. It describes the posted observations in the recorded groups and categories. The registry does not give information about event timing, severity grading beyond the serious category, duration, relatedness to vaccination, or completeness of safety follow-up. Its study summary describes collecting reaction information, but the posted safety figures do not supply those details.

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

The posted result supports a limited descriptive statement: the registry records zero participants with the primary adverse-event endpoint in each group during the one-year timeframe. It reports a risk difference of 0.0, with confidence limits of 0.0 and 0.0. The serious and other adverse-event entries likewise report zero affected participants in the listed groups.

That result does not establish that the vaccines have identical safety profiles. The record does not report event-level information, a detailed endpoint definition, missing-outcome handling, or the method used to calculate the confidence limits. A comparison with no observed events cannot characterize differences in event types or patterns that were not recorded. Nor does it establish that events cannot occur beyond the participants and period represented by the posted outcome.

The result also does not answer whether Towne CMV vaccine prevents CMV infection, changes immune responses, or affects pregnancy or children. Those topics appear in the study rationale and summary, but the posted primary result measures participants with adverse events. No secondary outcomes are posted in the registry record.

The record describes a randomized, double-blind, parallel-group phase II–III study, but does not provide detail on randomization methods, masking procedures, the analysis populations, or the statistical plan. It lists the study as terminated and does not report the reason. The registry enrollment is 82, while the brief summary describes 180 women as the number to be vaccinated; the record does not reconcile the figures.

Accordingly, the most defensible reading is confined to the registry-reported endpoint counts and comparison. Broader claims about safety, immune response, prevention, or the intended study population would require information not reported in the registry record.

14. Why This Trial Matters Statistically

This trial illustrates why a zero-event result needs more than a point estimate for full interpretation. The observed count is straightforward: the registry reports no participants with the primary adverse-event endpoint in either group. But understanding what that means also depends on the endpoint definition, follow-up completeness, analysis population, and method used to quantify uncertainty. Those details are not reported in the registry record.

It also shows the distinction between a posted result and a complete statistical analysis. The registry provides an outcome count and a risk difference with confidence limits, while listing no analysis entries and no p-value. The reported limits can be quoted, but their calculation cannot be checked from the information recorded. Statistical reporting is most informative when estimates are accompanied by enough method and population detail for readers to understand the assumptions behind them.

The population labels matter as well. The endpoint description says per protocol and randomized, but does not explain how those terms were implemented. Different analysis populations can answer different questions, so a clear account of who was included is important for interpreting even a simple count.

Finally, the study summary describes a broader program of sample collection and follow-up than the one-year primary endpoint alone. The gap between intended activities and posted outcome detail highlights the value of reporting which outcomes were completed, how much follow-up was observed, and why a terminated study ended. These statistical reporting issues are relevant even when the numerical result itself is easy to state.

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.

The registry provides limited detail for evaluating the primary adverse-event result. It does not define precisely which events counted, describe how they were solicited or adjudicated, or give event-level characteristics. The primary outcome timeframe is one year, while the study summary describes follow-up activities for up to 3 years; the record does not explain how those durations relate to the primary endpoint or whether one-year observation was complete.

The registry lists 82 participants enrolled and gives primary-outcome group counts of 42 and 40. The brief summary describes 180 women as the number to be vaccinated, and the record does not explain the difference. The reason for the terminated status is not reported, so its effect on recruitment, follow-up, or planned analyses cannot be assessed.

The analysis population is worded as per protocol and randomized without a detailed definition. There is no report of exclusions, protocol deviations, missing outcome counts, or missing-data methods. The registry also does not describe the statistical analysis plan, adjustment choices, interim analyses, or the method used for the confidence limits. No p-value or analysis entry is posted.

Only the primary adverse-event result is available for interpretation; no secondary outcomes are posted. The record does not provide a posted immune-response result, CMV infection outcome, or outcome for children. These gaps limit the scope of conclusions to the recorded one-year adverse-event counts and the reported group comparison.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Evaluation of the Safety and Immune Responses of the Towne Strain of CMV in Seronegative Women — NCT00201448.
• Registry record last updated 2016-05-30; status last verified 2016-05.
• Results first posted 2016-05-30.
• 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.

19. Record Summary

The registry describes a randomized, double-blind, parallel-group phase II–III study of Towne CMV vaccine versus hepatitis A vaccine in women who were seronegative for CMV. It lists 82 participants enrolled and identifies the study status as terminated. The reason for termination is not reported in the registry record.

The primary endpoint is participants with adverse events during one year, with the analysis population described as per protocol and randomized. The registry reports 0 among 42 participants in the hepatitis A group and 0 among 40 in the Towne CMV vaccine group. The reported risk difference is 0.0, with confidence limits of 0.0 and 0.0. No analysis entries or secondary outcomes are posted. The record does not report the confidence-interval method, missing-data handling, or detailed analysis-population definitions.