Active — Not RecruitingNot Applicable

Evaluating ABRYSVO Maternal Vaccine Effectiveness Among Infants

United States1 participantsStarted 2025-12-01

Plain-language 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 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.

Who can participate

Age range

0 Years – 50 Years

Sex

ALL

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AI-rewrites the medical criteria so a patient or caregiver can understand them. Always confirm with the trial site.

Inclusion criteria

. 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

Exclusion criteria

. Live birth
. Enrolled as member in KPNC by 4 months of age (membership indicated in any of months 2-4 of life)

Questions worth asking your doctor

Bring these to your next appointment. They're a starting point for a shared conversation — not a sign you qualify or a recommendation to enrol.

1Based on my diagnosis and history, is this trial worth exploring for me — or is there a standard treatment we should try first?
2What does this trial's phase tell us about how much is already known about its safety and benefit?
3What would taking part actually involve for me — visits, tests, time, and travel?
4What are the known and possible risks or side effects I should weigh, and how would they be monitored?
5If this trial isn't the right fit, what other options or trials would you suggest I look into?

Generated to help you prepare — always confirm anything about your own eligibility and care with the study team and your doctor.

Questions for the trial coordinator

The trial coordinator is the person who runs the study day to day. These cover the practical side — logistics, costs, and what taking part would actually mean for your life. The study team confirms whether you meet the criteria; these are questions to ask, not a sign you qualify.

1What does taking part actually involve week to week — how many visits, where, and how long does each one take?
2What costs are covered by the study, and what might I have to pay for myself, including travel, parking, or time off work?
3What happens during screening, and what happens if the study team confirms I don't meet the criteria after those tests?
4Who pays for the scans, blood work, and other tests the trial requires — the study, my insurance, or me?
5How will being in the trial affect my regular care, and will my own doctor stay informed and involved?
6Can I leave the trial at any point if I change my mind, and what would happen to my care if I do?

A starting point for the conversation — always confirm anything about your own eligibility, costs, and care with the study team and your doctor.

What they're measuring

Polymerase chain reaction (PCR)-confirmed RSV LRTD occurring ≤180 days after birth (first episode).

Timeframe: ≤180 days after birth

Trial details

NCT IDNCT07249320

SponsorPfizer

Sponsor typeINDUSTRY

Study typeOBSERVATIONAL

Primary completion2027-09-30

View on ClinicalTrials.gov More Respiratory Syncytial Virus (RSV) trials