NCT07249320

Evaluating ABRYSVO Maternal Vaccine Effectiveness Among Infants

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

• Status: Active Not Recruiting
• Phase: —
• Study type: Observational
• Enrollment: 39,456 (estimated)
• Sponsor: Pfizer · Industry
• Sex: All
• Age: 0 Years – 50 Years
• Healthy volunteers: —

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)

Interventions

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

Timeline

• Start date: 2025-12-01
• Primary completion: 2027-09-30
• Completion: 2027-09-30
• First posted: 2025-11-25
• Last updated: 2025-12-19

Locations

1 site across 1 country: United States

Regulatory

• FDA-regulated drug study