Evaluating ABRYSVO Maternal Vaccine Effectiveness Among Infants

NCT07249320 | Active Not Recruiting FDA Drug

• 1 other identifier: C3671048
• Study Type: observational
• Target: 39,456
• Locations: 1 country
• Sites: 1

Brief 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. The overall research question of this study is: what is the effectiveness of ABRYSVO vaccination during pregnancy against medically-attended (MA) 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 through 6 months of age, with later assessments from birth through 12 months of age and through 24 months 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 through 6 months of age, birth through 12 months of age, and/or birth through 24 months 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 new 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)

Keywords

Lower respiratory tract infections; acute respiratory tract infections; RSV; maternal immunization

Outcome Measures

Primary Outcomes (1)

• 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 through 6 months of age.

  ≤180 days after birth

Secondary Outcomes (11)

• Key Secondary 1: PCR-confirmed RSV LRTD hospitalization occurring ≤180 days after birth (first episode).

  ≤180 days after birth

• Secondary 1: PCR-confirmed RSV occurring ≤180 days after birth (first episode).

  ≤180 days after birth

• Secondary 2: PCR-confirmed RSV hospitalization occurring ≤180 days after birth (first episode).

  ≤180 days after birth

• Secondary 3: LRTD (any cause) occurring ≤180 days after birth (first episode during the RSV season).

  ≤180 days after birth

• Secondary 4: LRTD hospitalization (any cause) occurring ≤180 days after birth (first episode during the RSV season).

  ≤180 days after birth

Study Arms (2)

Exposed

Infants whose mother received ABRYSVO vaccine during pregnancy 14 days or more before delivery

Biological: ABRYSVO

Unexposed

Infants born to mothers who did not receive ABRYSVO during pregnancy will be considered unexposed

Interventions

ABRYSVO BIOLOGICAL

Participants will receive Pfizer's ABRYSVO vaccine as part of standard of care. Vaccine is not administered in this study.

Exposed

Eligibility Criteria

• Age: 0 Years - 50 Years
• Sex: all
• Age Groups: Child (0-17), Adult (18-64)
• Sampling Method: Non-Probability Sample

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.

You may qualify if:

• 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 1-month administrative gap in coverage

You may not qualify if:

• Live birth
• Enrolled as member in KPNC by 3 months of age
• 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

Sponsors & Collaborators

• Pfizer: lead

Study Sites (1)

Pfizer

New York, New York, 10001, United States

Location

Related Links

• To obtain contact information for a study center near you, click here.

MeSH Terms

Interventions

abrysvo

Study Officials

• Pfizer CT.gov Call Center

  Pfizer

  STUDY DIRECTOR

Study Design

• Study Type: observational
• Observational Model: COHORT
• Time Perspective: RETROSPECTIVE
• Sponsor Type: INDUSTRY
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: November 18, 2025
• First Posted: November 25, 2025
• Study Start: December 1, 2025
• Primary Completion (Estimated): September 30, 2027
• Study Completion (Estimated): September 30, 2027
• Last Updated: December 19, 2025

Record last verified: 2025-12

Data Sharing

• IPD Sharing: Will not share

Locations

US (1)