Respiratory Syncytial Virus (RSV)NCT07249320
Evaluating ABRYSVO Maternal Vaccine Effectiveness Among Infants
An observational study of Respiratory Syncytial Virus (RSV), run by Pfizer at 1 site in United States.
Trial summary
To generate critical evidence to support vaccine policy and implementation, Pfizer will collaborate with Kaiser Permanente Northern California (KPNC) to study the vaccine effectiveness (VE) of ABRYSVO vaccination during pregnancy in a real-world population. Read more about this study
- Who is it for?
- Ages 0 to 50 years
- Conditions the study is for
- Respiratory Syncytial Virus (RSV)
- What is being tested?
- ABRYSVO
- Type of treatment
- Vaccines
- How many people
- 1 participants
- Where
- 1 siteUnited States
- Study dates
- 1 Dec 2025to 30 Sep 2027
- 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 to 50 years
- All sexes
- Child, Adult
Study population: The study population will comprise eligible maternal-infant pairs over a 2-year study period, identified from EMR records in the existing databases, which accrue in real-time as pregnancies/births occur. All pregnancies that reach 32 0/7 weeks' gestation during the 2-year study period, from September 22, 2023 (start of ABRYSVO vaccination season 1) to January 31, 2025 (estimated end of ABRYSVO vaccination season 2) will be eligible for inclusion, along with all live born infants from the eligible pregnancies. The KPNC pregnancy database will be used to identify the maternal-infant study population. This database links records of newborn infants with their mother, enabling integration of maternal data from across pregnancy and delivery encounters, along with infant birth information and longitudinal follow-up for infants who remain enrolled with KPNC. Infant healthcare encounters after the birth and throughout the follow-up period will be identified in the EMR.
Who may be able to join
- Pregnant Individuals - Inclusion Criteria:
- Participants must meet all of the following inclusion criteria to be eligible for inclusion in the study:
- Gestational age at delivery ≥32 0/7 weeks of gestation (earliest gestational age eligible for ABRYSVO vaccination) during the study period
- Maternal age >/= 18 to 50 years at pregnancy onset
- At least 1 prenatal visit between pregnancy onset and 20 weeks of gestation
- Continuous KPNC enrollment for a minimum of 30 days prior to pregnancy onset through to the date of delivery, with no more than a 2-month administrative gap in coverage
Show all 11Show fewer
- Infants - Inclusion Criteria:
- Participants must meet all of the following inclusion criteria to be eligible for inclusion in the study:
- Born to a pregnant individual who has met all inclusion and exclusion criteria outlined above
- Live birth
- Enrolled as member in KPNC by 4 months of age (membership indicated in any of months 2-4 of life)
Who cannot join
- Pregnant Individuals - Exclusion Criteria:
- Participants meeting any of the following criteria will not be included in the study:
- Received any licensed or investigational RSV vaccine other than ABRYSVO at any time during pregnancy
- Received ABRYSVO at ≥37 weeks' gestation
- Received ABRYSVO at <32 0/7 weeks' gestation
- Infants - Exclusion Criteria:
- There are no exclusion criteria for infants. Those who receive any licensed or investigational RSV preventative product (e.g., monoclonal antibodies) at/after birth or any licensed or investigational RSV therapeutic (e.g., antiviral medications) will not be excluded, but their follow-up time will be censored on the date of receipt of the RSV preventative or therapeutic product.
Trial locations and contacts
1 site in 1 country.
About this study
Official title: OBSERVATIONAL COHORT STUDY EVALUATING REAL-WORLD ABRYSVO VACCINE EFFECTIVENESS AND IMPACT AGAINST MEDICALLY-ATTENDED RSV-RELATED AND ALL-CAUSE OUTCOMES AMONG INFANTS BORN TO INDIVIDUALS VACCINATED DURING PREGNANCY
To generate critical evidence to support vaccine policy and implementation, Pfizer will collaborate with Kaiser Permanente Northern California (KPNC) to study the vaccine effectiveness (VE) of ABRYSVO vaccination during pregnancy in a real-world population. The overall research question of this study is: what is the effectiveness and impact of ABRYSVO vaccination during pregnancy against medically-attended (MA) respiratory syncytial virus (RSV)-associated and all-cause infant outcomes in a large, diverse, real-world population? This study will use a retrospective cohort design and will be conducted within an integrated delivery health care organization using electronic medical record (EMR) data collected during routine standard of care clinical encounters. Study outcomes among infants born to ABRYSVO-vaccinated mothers (exposed group) will be compared with those among infants born to ABRYSVO-unvaccinated mothers (comparison group) initially from birth to ≤180 days of age, with later assessments from birth to ≤360 days of age and to ≤720 days of age as the infants reach these age thresholds and their data become available. There are two categories of outcomes of interest in this study: RSV-specific infant outcomes and non-specific all-cause infant outcomes, assessed within several follow-up windows (birth to ≤180 days of age, birth to ≤360 days of age, and/or birth to ≤720 days of age, depending on the outcome).
Identification of RSV-specific outcomes will be based on the first positive laboratory-confirmed PCR test from a respiratory specimen during a healthcare encounter in a KPNC healthcare setting, occurring during the relevant follow-up window. RSV-positive test results will be combined with International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) diagnostic codes to define the RSV-specific outcomes. RSV-specific outcomes will include: PCR-confirmed RSV, PCR-confirmed RSV hospitalization, PCR-confirmed RSV LRTD, and PCR-confirmed RSV LRTD hospitalization.
Non-specific all-cause infant outcomes will include: all-cause LRTD, all-cause LRTD hospitalization, acute otitis media, and first antibiotic prescription (for any diagnosis). Identification of these outcomes will be based on ICD-10-CM diagnostic codes documented in infant EMRs during a healthcare encounter in a KPNC healthcare setting, occurring during the relevant follow-up window.
- Conditions
- Respiratory Syncytial Virus (RSV)
- Being tested
- ABRYSVO
- Keywords
- Lower respiratory tract infections, acute respiratory tract infections, RSV, maternal immunization
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
ABRYSVOBiological
Participants will receive Pfizer's ABRYSVO vaccine as part of standard of care. Vaccine is not administered in this study.
| Study group | Role | What they receive |
|---|---|---|
| Exposed | Infants whose mother received ABRYSVO vaccine during pregnancy 14 days or more before delivery Receives: Biological: ABRYSVO | |
| Unexposed | Infants born to mothers who did not receive ABRYSVO during pregnancy will be considered unexposed |
What is being measured
The primary outcome is the main question the study is designed to answer.
Polymerase chain reaction (PCR)-confirmed RSV LRTD occurring ≤180 days after birth (first episode).
To estimate VE of ABRYSVO vaccination during pregnancy against RSV LRTD among infants from birth to ≤180 days of age.
Measured: ≤180 days after birth
Secondary outcomes (11)
Key Secondary 1: PCR-confirmed RSV LRTD hospitalization occurring ≤180 days after birth (first episode).
To estimate VE of ABRYSVO vaccination during pregnancy against RSV LRTD hospitalization among infants from birth to ≤180 days of age.
Measured: ≤180 days after birth
Secondary 1: PCR-confirmed RSV occurring ≤180 days after birth (first episode).
To estimate VE of ABRYSVO vaccination during pregnancy against RSV among infants from birth to ≤180 days of age.
Measured: ≤180 days after birth
Secondary 2: PCR-confirmed RSV hospitalization occurring ≤180 days after birth (first episode).
To estimate VE against RSV hospitalization among infants from birth to ≤180 days of age.
Measured: ≤180 days after birth
Secondary 3: LRTD (any cause) occurring ≤180 days after birth (first episode during the RSV season).
To estimate VE against all-cause LRTD among infants born in-season from birth through the RSV season (to ≤180 days of age).
Measured: ≤180 days after birth
Secondary 4: LRTD hospitalization (any cause) occurring ≤180 days after birth (first episode during the RSV season).
To estimate VE against all-cause LRTD hospitalization among infants born in-season from birth through the RSV season (to ≤180 days of age).
Measured: ≤180 days after birth
Secondary 5: Acute otitis media occurring ≤180 days after birth (first episode during the RSV season).
To estimate VE against acute otitis media among infants born in-season from birth through the RSV season (to ≤180 days of age).
Measured: ≤180 days after birth
Secondary 6: New antibiotic prescriptions occurring ≤180 days after birth (first prescription during the RSV season).
To estimate VE against new antibiotic prescriptions among infants born in-season from birth through the RSV season (to ≤180 days of age).
Measured: ≤180 days after birth
Secondary 7: PCR-confirmed RSV occurring ≤360 days after birth (first episode).
To estimate VE and interval-specific VE against RSV among infants from birth to ≤360 days of age.
Measured: ≤360 days after birth
Secondary 8: PCR-confirmed RSV hospitalization occurring ≤360 days after birth (first episode).
To estimate VE and interval-specific VE against RSV hospitalization among infants from birth to ≤360 days of age.
Measured: ≤360 days after birth
Secondary 9: PCR-confirmed RSV LRTD occurring ≤360 days after birth (first episode).
To estimate VE and interval-specific VE of ABRYSVO vaccination during pregnancy against RSV LRTD among infants from birth to ≤360 days of age.
Measured: ≤360 days after birth
Secondary 10: PCR-confirmed RSV LRTD hospitalization occurring ≤360 days after birth (first episode).
To estimate VE and interval-specific VE of ABRYSVO vaccination during pregnancy against RSV LRTD hospitalization among infants from birth to ≤360 days of age.
Measured: ≤360 days after birth
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted25 Nov 2025
- Study start1 Dec 2025
- Primary completion30 Sep 2027 (estimated)
- Study completion30 Sep 2027 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Respiratory Syncytial Virus (RSV)Studies 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
- Cohort
- Time perspective
- Retrospective
- Enrolment
- 1 participants (actual)
Sponsor and investigators
- Lead sponsor
- Pfizer
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
- Investigators
- Pfizer CT.gov Call Center, Study director, Pfizer
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07249320
- Sponsor's protocol ID
- C3671048
- Status last verified
- Jun 2026
- First submitted
- 18 Nov 2025
- Last updated
- 10 Jun 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 10 Jun 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- OBSERVATIONAL COHORT STUDY EVALUATING REAL-WORLD ABRYSVO VACCINE EFFECTIVENESS AND IMPACT AGAINST MEDICALLY-ATTENDED RSV-RELATED AND ALL-CAUSE OUTCOMES AMONG INFANTS BORN TO INDIVIDUALS VACCINATED DURING PREGNANCY
- ClinicalTrials.gov ID
- NCT07249320
- Acronym / sponsor ID
- C3671048
- Conditions
- Respiratory Syncytial Virus (RSV)
- Keywords
- Lower respiratory tract infections, acute respiratory tract infections, RSV, maternal immunization
- Study type
- Observational
- Recruitment status
- Active, not recruiting
- Enrolment
- 1 participants (actual)
- Lead sponsor
- PfizerIndustry (pharma, biotech, devices)
- Study start
- 1 Dec 2025 (actual)
- Primary completion
- 30 Sep 2027 (estimated)
- Study completion
- 30 Sep 2027 (estimated)
- First posted
- 25 Nov 2025 (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.
To generate critical evidence to support vaccine policy and implementation, Pfizer will collaborate with Kaiser Permanente Northern California (KPNC) to study the vaccine effectiveness (VE) of ABRYSVO vaccination during pregnancy in a real-world population. The overall research question of this study is: what is the effectiveness and impact of ABRYSVO vaccination during pregnancy against medically-attended (MA) respiratory syncytial virus (RSV)-associated and all-cause infant outcomes in a large, diverse, real-world population? This study will use a retrospective cohort design and will be conducted within an integrated delivery health care organization using electronic medical record (EMR) data collected during routine standard of care clinical encounters. Study outcomes among infants born to ABRYSVO-vaccinated mothers (exposed group) will be compared with those among infants born to ABRYSVO-unvaccinated mothers (comparison group) initially from birth to ≤180 days of age, with later assessments from birth to ≤360 days of age and to ≤720 days of age as the infants reach these age thresholds and their data become available. There are two categories of outcomes of interest in this study: RSV-specific infant outcomes and non-specific all-cause infant outcomes, assessed within several follow-up windows (birth to ≤180 days of age, birth to ≤360 days of age, and/or birth to ≤720 days of age, depending on the outcome).
Identification of RSV-specific outcomes will be based on the first positive laboratory-confirmed PCR test from a respiratory specimen during a healthcare encounter in a KPNC healthcare setting, occurring during the relevant follow-up window. RSV-positive test results will be combined with International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) diagnostic codes to define the RSV-specific outcomes. RSV-specific outcomes will include: PCR-confirmed RSV, PCR-confirmed RSV hospitalization, PCR-confirmed RSV LRTD, and PCR-confirmed RSV LRTD hospitalization.
Non-specific all-cause infant outcomes will include: all-cause LRTD, all-cause LRTD hospitalization, acute otitis media, and first antibiotic prescription (for any diagnosis). Identification of these outcomes will be based on ICD-10-CM diagnostic codes documented in infant EMRs during a healthcare encounter in a KPNC healthcare setting, occurring during the relevant follow-up window.
Study design
- Observational model
- Cohort
- Time perspective
- Retrospective
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Exposed | – | Biological: ABRYSVOInfants whose mother received ABRYSVO vaccine during pregnancy 14 days or more before delivery |
| Unexposed | – | –Infants born to mothers who did not receive ABRYSVO during pregnancy will be considered unexposed |
Who may qualify
- Ages
- 0 to 50 years
- Sex
- All
- Age groups
- Child, Adult
- Study population
- The study population will comprise eligible maternal-infant pairs over a 2-year study period, identified from EMR records in the existing databases, which accrue in real-time as pregnancies/births occur. All pregnancies that reach 32 0/7 weeks' gestation during the 2-year study period, from September 22, 2023 (start of ABRYSVO vaccination season 1) to January 31, 2025 (estimated end of ABRYSVO vaccination season 2) will be eligible for inclusion, along with all live born infants from the eligible pregnancies. The KPNC pregnancy database will be used to identify the maternal-infant study population. This database links records of newborn infants with their mother, enabling integration of maternal data from across pregnancy and delivery encounters, along with infant birth information and longitudinal follow-up for infants who remain enrolled with KPNC. Infant healthcare encounters after the birth and throughout the follow-up period will be identified in the EMR.
Key inclusion criteria (11 listed)
- Participants must meet all of the following inclusion criteria to be eligible for inclusion in the study:
- Gestational age at delivery ≥32 0/7 weeks of gestation (earliest gestational age eligible for ABRYSVO vaccination) during the study period
- Maternal age >/= 18 to 50 years at pregnancy onset
- At least 1 prenatal visit between pregnancy onset and 20 weeks of gestation
- Continuous KPNC enrollment for a minimum of 30 days prior to pregnancy onset through to the date of delivery, with no more than a 2-month administrative gap in coverage
Key exclusion criteria (7 listed)
- Received any licensed or investigational RSV vaccine other than ABRYSVO at any time during pregnancy
- Received ABRYSVO at ≥37 weeks' gestation
- Received ABRYSVO at <32 0/7 weeks' gestation
- There are no exclusion criteria for infants. Those who receive any licensed or investigational RSV preventative product (e.g., monoclonal antibodies) at/after birth or any licensed or investigational RSV therapeutic (e.g., antiviral medications) will not be excluded, but their follow-up time will be censored on the date of receipt of the RSV preventative or therapeutic product.
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 |
|---|---|---|
| ABRYSVOParticipants will receive Pfizer's ABRYSVO vaccine as part of standard of care. Vaccine is not administered in this study. | Biological | Exposed |
Primary outcome
Polymerase chain reaction (PCR)-confirmed RSV LRTD occurring ≤180 days after birth (first episode).
Time frame: ≤180 days after birth
To estimate VE of ABRYSVO vaccination during pregnancy against RSV LRTD among infants from birth to ≤180 days of age.
11 secondary outcomes
Key Secondary 1: PCR-confirmed RSV LRTD hospitalization occurring ≤180 days after birth (first episode).
Time frame: ≤180 days after birth
Secondary 1: PCR-confirmed RSV occurring ≤180 days after birth (first episode).
Time frame: ≤180 days after birth
Secondary 2: PCR-confirmed RSV hospitalization occurring ≤180 days after birth (first episode).
Time frame: ≤180 days after birth
Secondary 3: LRTD (any cause) occurring ≤180 days after birth (first episode during the RSV season).
Time frame: ≤180 days after birth
Secondary 4: LRTD hospitalization (any cause) occurring ≤180 days after birth (first episode during the RSV season).
Time frame: ≤180 days after birth
Secondary 5: Acute otitis media occurring ≤180 days after birth (first episode during the RSV season).
Time frame: ≤180 days after birth
Secondary 6: New antibiotic prescriptions occurring ≤180 days after birth (first prescription during the RSV season).
Time frame: ≤180 days after birth
Secondary 7: PCR-confirmed RSV occurring ≤360 days after birth (first episode).
Time frame: ≤360 days after birth
Secondary 8: PCR-confirmed RSV hospitalization occurring ≤360 days after birth (first episode).
Time frame: ≤360 days after birth
Secondary 9: PCR-confirmed RSV LRTD occurring ≤360 days after birth (first episode).
Time frame: ≤360 days after birth
Secondary 10: PCR-confirmed RSV LRTD hospitalization occurring ≤360 days after birth (first episode).
Time frame: ≤360 days after birth
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 10 Jun 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 (RSV), run by Pfizer at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 11 inclusion and 7 exclusion criteria. 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 10 Jun 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 United States. 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?
Polymerase chain reaction (PCR)-confirmed RSV LRTD occurring ≤180 days after birth (first episode). (time frame: ≤180 days after birth). 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 10 Jun 2026.