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 A Prospective, Epidemiological Study to Assess the Disease Burden of Respiratory Syncytial Virus Associated, Suspected Lower Respiratory Tract Infections in Newborns, From 0 to 2 Years of Age and Risk of Development of Wheeze and Asthma From 0 to 6 Years of Age (NCT01995175), a na na study. The primary outcome is Incidence Rates of First Episode of Respiratory Syncytial Virus (RSV) Respiratory Tract Infection (RTI) [Period 1].
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01995175 |
| Phase | NA |
| Condition | Respiratory Syncytial Virus |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 2409 |
| Arms in the primary outcome | n/a |
| Lead sponsor | GlaxoSmithKline |
| Results posted | Yes |
2. Clinical Question
Population
Newborn subjects were followed for suspected lower respiratory tract infection symptoms from birth until 2 years of age, and for wheeze and asthma incidence up to 6 years of age. The primary analysis population is described as the Per Protocol Set: enrolled subjects meeting eligibility criteria up to their censoring, whether at primary-study completion or earlier dropout.
Intervention
This was not a treatment comparison. Study procedures included nasal swab sampling, blood sampling, and diary cards. The study sought to observe respiratory infections and subsequent outcomes in a general population of infants, rather than to estimate the effect of an assigned therapy.
Comparator
There was no randomized control arm or like-for-like comparison group in the registry design. The study is recorded as a single-group study with allocation listed as NA. Some outcomes concern classification or severity definitions, but a comparative result for those definitions is not reported in the registry record.
Primary question
The primary question was the incidence rate of a first RSV respiratory tract infection from birth up to 2 years of age, expressed as cases per 100 person-years. The broader study also aimed to assess healthcare use related to RSV-associated suspected lower respiratory tract infection and the population attributable risk percent of RSV lower respiratory tract infection for later wheeze and asthma through 6 years of age.
3. Trial Design
This is a prospective epidemiological study of newborn subjects, not a randomized intervention trial. The registry identifies a single overall group, no masking, and allocation as NA. Its stated enrollment is 2409. The study began on 2013-12-12, has a primary completion date of 2017-10-03, and is recorded as completed. These record details describe the study status and planned observation period; they do not establish how many participants contributed to each endpoint analysis.
The overall group description says subjects were followed for lower respiratory tract infection symptoms from birth until 2 years of age, with wheeze and asthma incidence followed up to 6 years of age. The primary outcome timeframe is from birth up to 2 years of age. Nasal swabs were used for RSV detection, while blood sampling and diary cards are also listed as study procedures. The registry does not report the frequency or schedule of these procedures.
The study purpose included estimating incidence and associated healthcare utilization for RSV-associated suspected lower respiratory tract infection, assessing the accuracy of a newly developed case definition and severity scale against two existing definitions, and assessing the population attributable risk percent associated with RSV lower respiratory tract infection for later wheeze and asthma. These are observational aims. Without a randomized comparison, the design can describe occurrence and associations, but the registry design alone does not establish that RSV infection causes later respiratory outcomes.
The Per Protocol Set is described as including enrolled subjects who met eligibility criteria up to censoring, either at primary-study completion or earlier dropout, including withdrawal of consent or loss to follow-up. The number included in that analysis population and the number contributing person-time are not reported in the registry record. A protocol, detailed analysis plan, and further operational details 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.
Before assignment: Out of 2409 subjects enrolled in the primary study, 7 subjects did not sign the re-consent for study participation after delivery (birth), leaving 2402 subjects enrolled. 1 subject was excluded due to protocol violation, hence 2401 subjects formed the Per Protocol Set-Primary Study. Out of 2148 subjects who completed the primary study, 10 subjects were excluded due to invalid ICF/fraudulent data, 743 did not further participate, and therefore, 1395 subjects were enrolled in the extension study.
Period 1 - From 0 up to 2 Years of Age
| Stage | Overall Group |
|---|---|
| STARTED | 2401 |
| COMPLETED | 2148 |
| NOT COMPLETED | 253 |
Reasons for not completing this period:
| Reason | Overall Group |
|---|---|
| Withdrawal by Subject | 35 |
| Lost to Follow-up | 102 |
| Other | 67 |
| Migrated / moved from the study area | 49 |
Period 2 - From 2 up to 6 Years of Age
| Stage | Overall Group |
|---|---|
| STARTED | 1395 |
| COMPLETED | 1338 |
| NOT COMPLETED | 57 |
Reasons for not completing this period:
| Reason | Overall Group |
|---|---|
| Other | 21 |
| Lost to Follow-up | 22 |
| Migrated/moved from the study area | 6 |
| Consent withdrawal, not due to a Serious Adverse Event | 7 |
| Protocol Violation | 1 |
Analysis population for the primary outcome, as defined in the registry: The analysis was performed on the Per Protocol Set (PPS) which included all subjects enrolled in the primary study meeting all eligibility criteria up to the time of their censoring, either at completion of primary study or prematurely as drop-out (e.g., withdrawn consent, lost-to-follow-up).
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 | Overall Group |
|---|---|---|
| Participants analysed | 2401 | |
| Age, Customized: Gestational age at birth ≤28 weeks | Participants | 0 |
| Age, Customized: Gestational age at birth 29-32 weeks | Participants | 26 |
| Age, Customized: Gestational age at birth 33-36 weeks | Participants | 154 |
| Age, Customized: Gestational age at birth ≥37 weeks | Participants | 2221 |
| Age, Customized: 24 to 36 months of age | Participants | 1395 |
| Sex/Gender, Customized: Male | Participants | 704 |
| Sex/Gender, Customized: Female | Participants | 729 |
| Sex/Gender, Customized: Missing | Participants | 968 |
| Sex/Gender, Customized: Male | Participants | 687 |
| Sex/Gender, Customized: Female | Participants | 708 |
| Race/Ethnicity, Customized: Geographic ancestry – African Heritage / African American | Participants | 632 |
| Race/Ethnicity, Customized: Geographic ancestry – American Indian or Alaskan Native | Participants | 7 |
| Race/Ethnicity, Customized: Geographic ancestry – Asian - Central/South Asian Heritage | Participants | 5 |
| Race/Ethnicity, Customized: Geographic ancestry – Asian - East Asian Heritage | Participants | 4 |
| Race/Ethnicity, Customized: Geographic ancestry – Asian - Japanese Heritage | Participants | 1 |
| Race/Ethnicity, Customized: Geographic ancestry – Asian - South East Asian Heritage | Participants | 435 |
| Race/Ethnicity, Customized: Geographic ancestry – Latino/Mestizo | Participants | 303 |
| Race/Ethnicity, Customized: Geographic ancestry – Native Hawaiian or Other Pacific Islander | Participants | 3 |
| Race/Ethnicity, Customized: Geographic ancestry – African Heritage / African American | Participants | 386 |
| Race/Ethnicity, Customized: Geographic ancestry – American Indian or Alaskan Native | Participants | 4 |
| Race/Ethnicity, Customized: Geographic ancestry – Asian - Central/South Asian Heritage | Participants | 3 |
| Race/Ethnicity, Customized: Geographic ancestry – Asian - East Asian Heritage | Participants | 4 |
| Race/Ethnicity, Customized: Geographic ancestry – Asian - Japanese Heritage | Participants | 1 |
| Race/Ethnicity, Customized: Geographic ancestry – Asian - South East Asian Heritage | Participants | 271 |
| Race/Ethnicity, Customized: Geographic ancestry – Latino/Mestizo | Participants | 103 |
| Race/Ethnicity, Customized: Geographic ancestry – Native Hawaiian or Other Pacific Islander | Participants | 2 |
6. Primary Endpoint
The registry lists the primary outcome as Incidence Rates of First Episode of Respiratory Syncytial Virus (RSV) Respiratory Tract Infection (RTI) [Period 1], measured over From birth up to 2 years of age.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | 95% Confidence Interval |
| Unit | Cases per 100 person-years |
| Endpoint classification | Event-Rate Endpoint |
The primary endpoint is the incidence rate of a first episode of RSV respiratory tract infection from birth up to 2 years of age. It is expressed as cases per 100 person-years. The registry defines the rate as the number of subjects reporting a first episode over follow-up divided by total person-years. RSV infection detection was performed using a reverse transcription quantitative real time polymerase chain reaction assay on RNA extracted from nasal swabs, and the outcome description says suspected RSV respiratory tract infection cases were tabulated.
An incidence rate relates the occurrence of events to the time people were observed and at risk. In general, this makes it useful when follow-up duration differs among participants, as can happen when observation ends at study completion or earlier censoring. It is distinct from a simple proportion: the rate uses accumulated person-time as its denominator rather than only the number enrolled.
The endpoint focuses on the first episode, so it is not a measure of the total burden of all recurrent episodes. Nor, by itself, does it describe severity, healthcare utilization, or later wheeze and asthma. Those topics appear among the study aims and secondary outcomes, but their results are not reported in the registry record. The registry record also does not report the primary incidence estimate, event count, person-time total, or confidence interval, so the magnitude and precision of the primary outcome cannot be evaluated from this record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record specifies how the primary incidence rate was defined, but it does not report a numerical rate, the number of first RSV respiratory tract infection cases, total person-years, or a 95% confidence interval. Consequently, the primary result's size and statistical precision are not reported in the registry record. There is no basis in the record for describing the observed incidence as high or low, or for comparing it quantitatively with another population.
In general, an incidence rate summarizes how quickly events occur relative to observed time. Its interpretation depends on the population, event definition, observation period, and method used to identify cases. Here, the stated population is the Per Protocol Set and the endpoint description refers to suspected RSV respiratory tract infection cases, with detection by RT-qPCR from nasal swabs. The record does not provide enough numerical detail to assess how the resulting rate was distributed across ages or participant subgroups.
A confidence interval, in general, gives a range of values compatible with the data under the statistical procedure used. A narrower interval indicates greater precision for that estimate, while a wider interval indicates more uncertainty. Although the primary outcome identifies a 95% confidence interval as its dispersion measure, its limits are not reported in the registry record. Thus, precision cannot be characterized from the posted record. A confidence interval would not, on its own, address possible bias in case ascertainment, follow-up, or the composition of the analysis population.
The wider study aims concern healthcare utilization, severity classifications, neutralizing antibody levels, and later wheeze and asthma. The record lists secondary outcomes in these areas, including incidence rates for medically attended wheeze and wheeze or asthma requiring hospital admission. It does not provide their numerical results or the population attributable risk percent estimate. As a result, the record does not establish the frequency of those outcomes or quantify any association between early RSV infection and later respiratory outcomes.
The study has no randomized comparator group in its recorded design. Associations from an observational cohort can be informative about patterns of disease and can support estimation of incidence, but they may also reflect differences among participants that are related to both exposure and outcome. The registry record does not report adjusted estimates or enough analysis detail to assess confounding control. It therefore supports describing the study questions and endpoint definitions, not drawing a causal conclusion about later wheeze or asthma.
The completion status indicates that the study is recorded as completed, but it should not be confused with a complete account of findings. The numerical results needed to interpret the primary endpoint are not reported in the registry record. Accordingly, conclusions about the observed disease burden, precision, subgroup patterns, and relationships to later outcomes remain undetermined from this record.
9. Statistical Methods Explained
Incidence rate is the primary statistical concept in this study. In general, an incidence rate counts events relative to the amount of time participants contribute while under observation. The registry defines the primary rate using the number of subjects reporting a first episode and total person-years, with the result expressed as cases per 100 person-years. This allows the rate to reflect unequal observation time, rather than treating all participants as if they had identical follow-up.
The endpoint is a first episode, so the event being counted is not every infection episode across follow-up. In general, for a first-event rate, observation for an individual contributes time until the event or the end of the relevant observation period. The registry states that the Per Protocol Set includes eligible enrolled subjects through censoring at study completion or earlier dropout. It does not specify further details of time-at-risk construction or censoring rules in the registry record.
What does the confidence interval communicate?
In general, a confidence interval describes statistical uncertainty around an estimate, under the assumptions of the method used to calculate it. The primary outcome names a 95% confidence interval as its dispersion measure. The interval limits and underlying estimate are not reported in the registry record. Without those quantities, readers cannot assess the numerical range of values compatible with the observed data under that method.
A confidence interval and an estimate answer different questions. The rate is the estimated event frequency relative to person-time; the interval describes the precision of that estimate. Neither alone ensures that the case definition is valid, that all relevant cases were detected, or that the analysis population represents a broader population. Those considerations require study and analysis details beyond the interval itself.
How does case ascertainment affect interpretation?
The primary outcome description says RSV infection was detected by reverse transcription quantitative real time polymerase chain reaction on RNA extracted from nasal swabs. It also says suspected RSV respiratory tract infection cases were tabulated. In general, an endpoint combining a clinical case definition with a laboratory test depends on both the criteria used to identify a suspected respiratory infection and the performance and timing of the test. The registry purpose mentions assessment of a newly developed lower respiratory tract infection case definition and severity scale compared with two existing definitions, but the comparison methods and results are not reported in the registry record.
The distinction between respiratory tract infection and lower respiratory tract infection matters for reading the record: the primary outcome is titled as RSV respiratory tract infection, while the broader study purpose describes suspected lower respiratory tract infections and their burden. The registry endpoint description should therefore be read as written, without assuming that every suspected lower respiratory tract event was confirmed or that all definitions yielded identical classifications.
What do person-time and censoring imply?
Person-time is the sum of observation time contributed by participants. In general, it can accommodate differing follow-up lengths, but interpretation still depends on why follow-up ends and whether participants who stop being observed differ meaningfully from those who remain. The record names completion and premature dropout as censoring circumstances, with examples of withdrawn consent and loss to follow-up. It does not report counts or person-time by censoring reason, or a sensitivity analysis for incomplete follow-up.
For an incidence rate to be interpretable, both its numerator and denominator need to be understood. The registry describes the numerator concept and denominator concept, but does not report the actual case count or person-years. The enrollment figure of 2409 is not a substitute for either quantity: enrollment counts participants, whereas the rate's denominator is accumulated follow-up time and its numerator is first episodes.
Why does the design matter?
In general, a prospective cohort design observes outcomes as follow-up proceeds, rather than assigning participants to randomized treatment groups. This design is suited to describing incidence over time and investigating associations between exposures and later outcomes. It does not eliminate confounding. For the study's question about population attributable risk percent, interpretation also depends on how exposure, outcome, and relevant covariates are defined and analyzed. Those methods and the resulting estimate are not reported in the registry record.
The registry lists 15 outcome measures and zero analysis entries. This is a description of the registry record, not proof that no analyses were conducted. It does mean that inferential details such as model specification, covariate adjustment, handling of repeated or competing events, and planned subgroup analyses cannot be established from the recorded analysis entries. A statistical analysis plan is not reported in the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 15 outcome measures, including the primary incidence endpoint and secondary outcomes covering antibody levels, lower respiratory tract infection episodes and severity, and later wheeze-related outcomes. When a study evaluates multiple outcomes, general statistical practice recognizes that the chance of at least one apparently notable result may increase if many separate tests are interpreted without accounting for multiplicity. Whether any adjustment or hierarchy was planned in this study is not reported in the registry record. The record lists zero analysis entries, which does not establish whether or how investigators conducted analyses.
Missing-data handling is also not described in sufficient detail to evaluate. The Per Protocol Set is defined through censoring at study completion or earlier dropout, with examples including withdrawal of consent and loss to follow-up. The record does not report how many participants were censored for each reason, whether outcome status was missing for any participant, or what assumptions or methods were used to address missing outcome or covariate information. The consequences of missingness for the incidence estimate therefore cannot be assessed from this record.
The primary analysis population is described as the Per Protocol Set, but the number analyzed is not reported in the registry record. The registry also does not give the number of participants with evaluable nasal swabs, the number with observed first episodes, or the total person-time. Without these details, readers cannot reconcile the enrollment figure with the population contributing to the primary estimate.
Interim analyses, stopping rules, a prespecified statistical analysis plan, and sample-size justification are not reported in the registry record. These gaps limit assessment of prespecification and selective reporting. They do not demonstrate that any particular practice was or was not used; they mean that it cannot be verified from the record.
11. What the Result Does, and Does Not, Mean
The study is designed to describe the occurrence of RSV-associated respiratory infection during early life and to examine later respiratory outcomes. Its primary endpoint is an incidence rate of first RSV respiratory tract infection, measured per person-time, rather than a treatment effect. The registry record provides the endpoint definition, the general analysis population, and the intended timeframe, but does not provide the numerical rate or its 95% confidence interval.
Therefore, the record does not allow readers to quantify the observed primary disease burden or judge how precisely it was estimated. The record also does not provide numerical results for healthcare utilization, the proposed comparison of case definitions and severity scales, or population attributable risk percent for later wheeze and asthma. Those outcomes are part of the stated study purpose or listed outcomes, but their findings cannot be inferred from their presence in the registry.
In general, a prospective observational study can document event occurrence and explore relationships over time. It cannot by design guarantee that an observed association is causal, because participant characteristics and other factors may influence both exposure and outcome. No randomized comparator is recorded. The registry does not report adjusted estimates or sufficient details to determine how confounding was addressed.
The completed status and enrollment of 2409 describe the study record, not the number analyzed for every endpoint or the certainty of any result. Likewise, a stated follow-up period does not establish that each participant was observed for the full period. The registry describes censoring at completion or earlier dropout, but does not report the extent of follow-up or losses for the primary analysis.
In general, results from an epidemiological cohort may help characterize patterns in the population studied, but applying them to other populations requires attention to differences in eligibility, case ascertainment, follow-up, and setting. The registry record does not report enough detail or results to determine the magnitude of findings or their transportability. The appropriate interpretation is limited to the study's stated questions and methods; claims about the observed frequency, later risk, or causal effect are not supported by the numerical information recorded.
12. Why This Trial Matters Statistically
Statistically, the study asks a question that depends on time as well as event counts. An incidence rate uses person-years to account for the amount of observation contributed, which is relevant when participants can leave follow-up at different times. The registry explicitly defines the primary measure this way and identifies first RSV respiratory tract infection as the event of interest.
The record also illustrates why the endpoint's operational definition matters. Respiratory infection was assessed using nasal swab RT-qPCR, while suspected RSV respiratory tract cases were tabulated. The wider study sought to compare a newly developed case definition and severity scale with existing definitions. Different classification rules can affect who counts as a case, and therefore can affect an incidence estimate. The results of that assessment are not reported in the registry record.
The follow-up questions extend beyond early infection to wheeze and asthma through 6 years of age. A prospective cohort can support analysis of temporal patterns and associations, but later outcomes require attention to confounding, loss to follow-up, and endpoint definitions. The design's single group and lack of a randomized comparator make causal interpretation particularly dependent on careful observational analysis.
Finally, statistical interpretation requires reported estimates and uncertainty, not only an endpoint definition. The registry record does not report the primary rate, its confidence interval, the event count, or the person-time denominator. This means that readers can understand what the study intended to estimate, but cannot judge its observed magnitude or precision from the registry record. That distinction is central to reading any epidemiological study: a clear question and a completed study record do not themselves provide the numerical evidence needed to quantify a result.
13. 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 main limitation for interpreting the registry record is the absence of numerical primary results. Although the outcome is defined as a first-episode incidence rate per 100 person-years with a 95% confidence interval, neither the estimate nor interval is reported in the registry record. The event count and person-time denominator are also not reported, preventing independent review of the rate's components.
The analysis population is described as the Per Protocol Set, but its size is not reported. Enrollment is 2409; this does not show how many subjects contributed to the primary endpoint analysis or how much follow-up they contributed. The registry notes that censoring could occur at primary-study completion or earlier dropout, including withdrawal of consent and loss to follow-up, but does not report the amount or pattern of such censoring.
The registry's primary endpoint refers to RSV respiratory tract infection and suspected cases, while the broader study purpose focuses on suspected lower respiratory tract infection. Although RT-qPCR testing is described, the record does not provide the operational case-definition details, testing schedule, or numerical evaluation of the case definition and severity scale. This limits assessment of how classification and ascertainment may have influenced the outcome.
The study is observational and has no recorded randomized comparator. The record does not report adjusted effect estimates or a detailed analysis plan, so confounding control and model choices cannot be assessed. Results for the later wheeze and asthma questions and for other listed outcomes are also not reported in the registry record. These limitations concern what can be concluded from the registry record; they do not establish that the full study lacked additional analyses or documentation elsewhere.
14. Related Tutorials
15. Related Statistical Calculators
16. Sources
- ClinicalTrials.gov: A Prospective, Epidemiological Study to Assess the Disease Burden of Respiratory Syncytial Virus Associated, Suspected Lower Respiratory Tract Infections in Newborns, From 0 to 2 Years of Age and Risk of Development of Wheeze and Asthma From 0 to 6 Years of Age — NCT01995175.
- Registry record last updated 2022-11-29; status last verified 2022-11.
- Results first posted 2019-02-15.
- 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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17. Record Summary
NCT01995175 is a completed prospective epidemiological study sponsored by GlaxoSmithKline. It records enrollment of 2409, a start date of 2013-12-12, and primary completion on 2017-10-03. The design is a single group, with no masking and allocation listed as NA.
Newborn subjects were followed for lower respiratory tract infection symptoms from birth to 2 years of age and for wheeze and asthma incidence up to 6 years of age. The primary endpoint is the incidence rate of a first RSV respiratory tract infection from birth up to 2 years, expressed as cases per 100 person-years and defined using person-time and a 95% confidence interval. RSV detection is described using RT-qPCR on nasal swab samples.
The study also aimed to assess healthcare utilization, case-definition and severity-scale accuracy, antibody levels, and the relationship between RSV lower respiratory tract infection and later wheeze and asthma. Numerical primary and secondary results are not reported in the registry record. The Per Protocol Set is described, but its size and the primary event count and person-time are not reported.