Respiratory Syncytial VirusBERNINCT06647654
Impact and Effectiveness of ABRYSVO® Vaccination During Pregnancy
An observational study of Respiratory Syncytial Virus and Respiratory Tract Diseases, run by Pfizer at 1 site in Argentina.
Trial summary
This study will be conducted in collaboration with a research network of independent hospital sites to evaluate the vaccine effectiveness (VE) and impact of ABRYSVO vaccination during pregnancy in a real-world population over multiple seasons, which began in 2024 across Argentina and beginning in 2025 in Uruguay. Read more about this study
- Who is it for?
- Ages 0 years to 24 months
- Conditions the study is for
- Respiratory Syncytial Virus, Respiratory Tract Diseases
- What is being tested?
- ABRYSVO
- Type of treatment
- Vaccines
- How many people
- 1 participants
- Where
- 1 siteArgentina
- Study dates
- 26 Aug 2024to 15 Oct 2026
- Phase
- Observational
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 0 years to 24 months
- All sexes
- No healthy volunteers
- Child
Study population: Test Negative Design: All infants through 9 months of age who were admitted to one of the participating hospital sites with symptoms of respiratory infection, born at 32 weeks of gestational age or greater, met the definition of LRTD, had a respiratory specimen collected with an RSV test result through standard of care testing, born 14 days or more after start of the first seasonal ABRYSVO vaccination campaign, and born to individuals who were expected to reach the indicated ABRYSVO vaccination window during a local ABRYSVO vaccination season. Cohort Design: RSV positive cases from the TND study. Ecologic Before-and-After Design: All infants and children ≤24 months of age admitted to one of the participating hospital sites and meeting eligibility criteria.
Test Negative Design Inclusion Criteria:
- Infants ≤9 months (≤270 days) of age on the index date.
- Index date within the time period for data collection (approximately 01 April to 30 September in 2024, 2025, or 2026).
- Infants born at 32 weeks of gestational age or greater.
- Hospitalized for at least 24 hours with LRTD (symptoms related to LRTD might be absent at the time of admission but if they develop within the first 24 hours of hospitalization, the criteria for LTRD will be considered met), and specimen collected for RSV within 10 days prior to hospital admission through 3 days after a hospital admission through SOC testing.
- Infant date of birth 14 days or more after start of the first seasonal ABRYSVO vaccination campaign, to ensure potential to have been born to an ABRYSVO-vaccinated individual.
- Infant born to individuals who were expected (based on estimated date of delivery) to reach the indicated ABRYSVO vaccination window (320/7 to 366/7 weeks' gestation) during a local ABRYSVO vaccination season.
Test Negative Design Exclusion Criteria:
- Received any licensed or investigational RSV preventive product (e.g., Palivizumab, Nirsevimab, active RSV vaccine) since birth.
- Received ≥1 blood transfusion or other blood products containing antibody (e.g., fresh frozen plasma) since birth.
- Born to individual who received any other licensed or investigational RSV vaccine during pregnancy.
- Born to individual for whom ABRYSVO vaccination status cannot be confirmed in available data sources.
- Infants with LRTD that require hospitalization for reasons other than clinical criteria (e.g., for social reasons, other medical condition in an infant with LRTD without hospitalization criteria).
Cohort Design Inclusion Criteria:
- RSV positive cases ≤9 months of age from the TND study.
Cohort Design Exclusion Criteria: None.
Ecologic Before-and-After Design Inclusion Criteria:
- Infants and children ≤24 months of age on the index date.
- Index date during the calendar years for data collection (pre- or post-ABRYSVO program implementation.
- Meets ≥1 outcome definition during the time period for data collection.
Ecologic Before-and-After Design Exclusion Criteria: None.
Trial locations and contacts
1 site in 1 country.
About this study
Official title: Real World Impact and Effectiveness of ABRYSVO® Vaccination During Pregnancy Against RSV Illness in Infants
This study will be conducted in collaboration with a research network of independent hospital sites to evaluate the vaccine effectiveness (VE) and impact of ABRYSVO vaccination during pregnancy in a real-world population over multiple seasons, which began in 2024 across Argentina and beginning in 2025 in Uruguay. We will use three retrospective design approaches in this study:
(i) a test negative design (TND) to evaluate real-world VE of maternal ABRYSVO against RSV-associated outcomes in infants;
Read more
(ii) a descriptive cohort design to evaluate the clinical evolution of infants hospitalized with RSV-positive lower respiratory tract disease (LRTD); and
(iii) an ecologic before-and-after design to evaluate the impact of ABRYSVO vaccination during pregnancy on infant RSV-associated and all-cause respiratory outcomes.
Read the detailed description
This hospital-based retrospective study will be conducted in a research network of independent hospital sites. We will collect data from hospital medical records, supplemented with information from vaccine registries. This study will use three retrospective design approaches: a test negative design (TND) to evaluate real-world vaccine effectiveness (VE) of maternal ABRYSVO against RSV-associated LRTD hospitalization and other outcomes in infants, a descriptive cohort design to evaluate the clinical features of infants hospitalized with RSV-positive LRTD, and an ecologic before-and-after design to evaluate the impact of ABRYSVO vaccination during pregnancy on infant RSV-associated and all-cause respiratory outcomes.
The TND study will include infants through 9 months of age who were admitted to one of the participating hospital sites with symptoms of respiratory infection, born at 32 weeks of gestational age or greater, met the definition of LRTD, had a respiratory specimen collected with an RSV test result through standard of care testing, born 14 days or more after start of the first seasonal ABRYSVO vaccination campaign, and born to individuals who were expected to reach the indicated ABRYSVO vaccination window during a local ABRYSVO vaccination season. To complement the VE estimates generated in the TND study, we will use the cases from the primary objective of the TND analysis as a cohort of participants to describe the endpoints in the descriptive cohort study. The ecologic before-and-after study will include information for infants and children ≤24 months of age meeting eligibility criteria in post-ABRYSVO program implementation years and in several historical RSV seasons pre-ABRYSVO program implementation.
For the TND study, a multivariable logistic regression model, adjusted for confounding, will be used to compute an adjusted odds ratio (aOR), comparing the odds of maternal ABRYSVO vaccination during pregnancy between test-positive cases and test-negative controls. VE will be estimated as (1-aOR) x 100%. Secondary and exploratory objectives will evaluate VE estimates stratified by several characteristics. For the descriptive cohort study of RSV-positive LRTD hospitalized infants ≤9 months of age (i.e., the cases from the primary objective of the TND study), infant characteristics, timing, severity/clinical features, and use of healthcare resources during the index hospitalization will be described. For the ecologic before-and-after study, the impact of maternal ABRYSVO introduction on rates of RSV-associated and all-cause outcomes among infants ≤6 months (compared with older age groups) over multiple RSV seasons will be described overall and by epidemiological week, calendar year, calendar month, age group, and hospital site. These analyses will begin in the 2024 RSV season in Argentina and continue in future RSV seasons in Argentina and Uruguay (2025 and 2026), with comparison to several pre-ABRYSVO implementation seasons. Quasi-experimental approaches will also be used to quantitatively compare incidence of study outcomes among infants aged ≤6 months with older age groups.
- Being tested
- ABRYSVO
- Keywords
- Vaccine, Effectiveness, Pregnancy, Maternal, Immunization, ABRYSVO, Respiratory Syncytial Virus, Lower respiratory tract disease, Infants, Hospitalized, Hospitalization, Test Negative Design, Case control, Retrospective, Cohort, Ecologic, Respiratory outcomes, Prefusion F protein-based
- Medical subject headings
- Respiratory Tract Diseases
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
ABRYSVOBiological
Test Negative Design: This is a non-interventional retrospective study; therefore, ABSYRVO vaccine has already been administered according to the standard of care. ABRYSVO is a bivalent RSV prefusion F protein-based vaccine (RSVpreF) composed of two prefusion F proteins to protect against both RSV-A and RSV-B.
Ecologic Before-and-After Design: This is an ecologic before-and-after study using aggregated data; as such, the 'exposure' of interest is time before ABRYSVO program implementation (i.e., five historical pre-ABRYSVO RSV seasons) and time after ABRYSVO implementation (i.e., post-ABRYSVO RSV seasons: 2024-2026).
| Study group | Role | What they receive |
|---|---|---|
| Cases (Test Negative Design and Cohort Design) | Infants who meet the respiratory case definition and test positive for RSV (result obtained from standard of care (SOC) testing). Receives: Biological: ABRYSVO | |
| Controls (Test Negative Design) | Infants who meet the respiratory case definition and test negative for RSV (result obtained from standard of care (SOC) testing). Receives: Biological: ABRYSVO | |
| Ecologic Cohort (Ecologic Before-and-After Design) | Aggregated data on study outcomes from five historical RSV seasons and from 2024-2026 RSV seasons (data during the COVID-19 pandemic are excluded). Receives: Biological: ABRYSVO |
What is being measured
The primary outcome is the main question the study is designed to answer.
RSV-associated LRTD hospitalization among infants
Lab-confirmed RSV-positive LRTD hospitalization occurring ≤180 days after birth
Measured: From birth through 6 months of age
Secondary outcomes (2)
RSV-associated severe LRTD hospitalization among infants
Lab-confirmed RSV-positive severe LRTD hospitalization occurring ≤180 days after birth
Measured: From birth through 6 months of age
RSV-associated LRTD hospitalization among infants, stratified by temporal and clinical characteristics
Lab-confirmed RSV-positive LRTD hospitalization occurring ≤180 days after birth
Measured: From birth through 6 months of age
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted18 Oct 2024
- Study start26 Aug 2024
- Primary completion1 Oct 2026 (estimated)
- Study completion15 Oct 2026 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Respiratory Syncytial VirusStudies of the same condition, open and under way.
- More trials run by PfizerThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Observational
- Observational model
- Case-control
- Time perspective
- Retrospective
- Enrolment
- 1 participants (actual)
Sponsor and investigators
- Lead sponsor
- Pfizer
- Sponsor type
- Industry (pharma, biotech, devices)
- Collaborators
- iTrials S.A.
- Responsible party
- Sponsor
- Investigators
- Pfizer CT.gov Call Center, Study director, Pfizer
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06647654
- Sponsor's protocol ID
- C3671068
- Other IDs
- NCT06647654
- Acronym
- BERNI
- Status last verified
- May 2026
- First submitted
- 16 Oct 2024
- Last updated
- 15 May 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- No: Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical\_trials/trial\_data\_and\_results/data\_requests.
Study at a glance
From the registry record, last updated by the sponsor on 15 May 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Real World Impact and Effectiveness of ABRYSVO® Vaccination During Pregnancy Against RSV Illness in Infants
- ClinicalTrials.gov ID
- NCT06647654
- Acronym / sponsor ID
- BERNI / C3671068
- Keywords
- Vaccine, Effectiveness, Pregnancy, Maternal, Immunization, ABRYSVO, Respiratory Syncytial Virus, Lower respiratory tract disease
- Study type
- Observational
- Recruitment status
- Active, not recruiting
- Enrolment
- 1 participants (actual)
- Lead sponsor
- PfizerIndustry (pharma, biotech, devices)
- Collaborators
- iTrials S.A.
- Study start
- 26 Aug 2024 (actual)
- Primary completion
- 1 Oct 2026 (estimated)
- Study completion
- 15 Oct 2026 (estimated)
- First posted
- 18 Oct 2024 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
This study will be conducted in collaboration with a research network of independent hospital sites to evaluate the vaccine effectiveness (VE) and impact of ABRYSVO vaccination during pregnancy in a real-world population over multiple seasons, which began in 2024 across Argentina and beginning in 2025 in Uruguay. We will use three retrospective design approaches in this study:
(i) a test negative design (TND) to evaluate real-world VE of maternal ABRYSVO against RSV-associated outcomes in infants;
(ii) a descriptive cohort design to evaluate the clinical evolution of infants hospitalized with RSV-positive lower respiratory tract disease (LRTD); and
(iii) an ecologic before-and-after design to evaluate the impact of ABRYSVO vaccination during pregnancy on infant RSV-associated and all-cause respiratory outcomes.
Detailed description
This hospital-based retrospective study will be conducted in a research network of independent hospital sites. We will collect data from hospital medical records, supplemented with information from vaccine registries. This study will use three retrospective design approaches: a test negative design (TND) to evaluate real-world vaccine effectiveness (VE) of maternal ABRYSVO against RSV-associated LRTD hospitalization and other outcomes in infants, a descriptive cohort design to evaluate the clinical features of infants hospitalized with RSV-positive LRTD, and an ecologic before-and-after design to evaluate the impact of ABRYSVO vaccination during pregnancy on infant RSV-associated and all-cause respiratory outcomes.
The TND study will include infants through 9 months of age who were admitted to one of the participating hospital sites with symptoms of respiratory infection, born at 32 weeks of gestational age or greater, met the definition of LRTD, had a respiratory specimen collected with an RSV test result through standard of care testing, born 14 days or more after start of the first seasonal ABRYSVO vaccination campaign, and born to individuals who were expected to reach the indicated ABRYSVO vaccination window during a local ABRYSVO vaccination season. To complement the VE estimates generated in the TND study, we will use the cases from the primary objective of the TND analysis as a cohort of participants to describe the endpoints in the descriptive cohort study. The ecologic before-and-after study will include information for infants and children ≤24 months of age meeting eligibility criteria in post-ABRYSVO program implementation years and in several historical RSV seasons pre-ABRYSVO program implementation.
For the TND study, a multivariable logistic regression model, adjusted for confounding, will be used to compute an adjusted odds ratio (aOR), comparing the odds of maternal ABRYSVO vaccination during pregnancy between test-positive cases and test-negative controls. VE will be estimated as (1-aOR) x 100%. Secondary and exploratory objectives will evaluate VE estimates stratified by several characteristics. For the descriptive cohort study of RSV-positive LRTD hospitalized infants ≤9 months of age (i.e., the cases from the primary objective of the TND study), infant characteristics, timing, severity/clinical features, and use of healthcare resources during the index hospitalization will be described. For the ecologic before-and-after study, the impact of maternal ABRYSVO introduction on rates of RSV-associated and all-cause outcomes among infants ≤6 months (compared with older age groups) over multiple RSV seasons will be described overall and by epidemiological week, calendar year, calendar month, age group, and hospital site. These analyses will begin in the 2024 RSV season in Argentina and continue in future RSV seasons in Argentina and Uruguay (2025 and 2026), with comparison to several pre-ABRYSVO implementation seasons. Quasi-experimental approaches will also be used to quantitatively compare incidence of study outcomes among infants aged ≤6 months with older age groups.
Study design
- Observational model
- Case-control
- Time perspective
- Retrospective
- Number of arms
- 3
| Arm | Type | Receives |
|---|---|---|
| Cases (Test Negative Design and Cohort Design) | – | Biological: ABRYSVOInfants who meet the respiratory case definition and test positive for RSV (result obtained from standard of care (SOC) testing). |
| Controls (Test Negative Design) | – | Biological: ABRYSVOInfants who meet the respiratory case definition and test negative for RSV (result obtained from standard of care (SOC) testing). |
| Ecologic Cohort (Ecologic Before-and-After Design) | – | Biological: ABRYSVOAggregated data on study outcomes from five historical RSV seasons and from 2024-2026 RSV seasons (data during the COVID-19 pandemic are excluded). |
Who may qualify
- Ages
- 0 years to 24 months
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Child
- Study population
- Test Negative Design: All infants through 9 months of age who were admitted to one of the participating hospital sites with symptoms of respiratory infection, born at 32 weeks of gestational age or greater, met the definition of LRTD, had a respiratory specimen collected with an RSV test result through standard of care testing, born 14 days or more after start of the first seasonal ABRYSVO vaccination campaign, and born to individuals who were expected to reach the indicated ABRYSVO vaccination window during a local ABRYSVO vaccination season. Cohort Design: RSV positive cases from the TND study. Ecologic Before-and-After Design: All infants and children ≤24 months of age admitted to one of the participating hospital sites and meeting eligibility criteria.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| ABRYSVOTest Negative Design: This is a non-interventional retrospective study; therefore, ABSYRVO vaccine has already been administered according to the standard of care. ABRYSVO is a bivalent RSV prefusion F protein-based vaccine (RSVpreF) composed of two prefusion F proteins to protect against both RSV-A and RSV-B. Ecologic Before-and-After Design: This is an ecologic before-and-after study using aggregated data; as such, the 'exposure' of interest is time before ABRYSVO program implementation (i.e., five historical pre-ABRYSVO RSV seasons) and time after ABRYSVO implementation (i.e., post-ABRYSVO RSV seasons: 2024-2026). | Biological | Cases (Test Negative Design and Cohort Design), Controls (Test Negative Design), Ecologic Cohort (Ecologic Before-and-After Design) |
Primary outcome
RSV-associated LRTD hospitalization among infants
Time frame: From birth through 6 months of age
Lab-confirmed RSV-positive LRTD hospitalization occurring ≤180 days after birth
2 secondary outcomes
RSV-associated severe LRTD hospitalization among infants
Time frame: From birth through 6 months of age
RSV-associated LRTD hospitalization among infants, stratified by temporal and clinical characteristics
Time frame: From birth through 6 months of age
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 15 May 2026.
- To obtain contact information for a study center near you, click here.Link provided by the sponsor.
- Individual participant dataSharing planned: No. Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical_trials/trial_data_and_results/data_requests.
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Pfizer CT.gov Call Center study director
Pfizer
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
An observational study of Respiratory Syncytial Virus and Respiratory Tract Diseases, run by Pfizer at 1 site in Argentina.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: under way, not looking for participants, as of the sponsor's last update on 15 May 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Argentina. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
RSV-associated LRTD hospitalization among infants (time frame: From birth through 6 months of age). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 15 May 2026.