Impact and Effectiveness of ABRYSVO® Vaccination During Pregnancy

NCT06647654 | Active Not Recruiting FDA Drug

• 2 other identifiers: C3671068NCT06647654
• Study Type: observational
• Target: 1
• Locations: 1 country
• Sites: 1

Brief 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. 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.

Conditions

Respiratory Syncytial Virus; Respiratory Tract Diseases

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

Outcome Measures

Primary Outcomes (1)

• RSV-associated LRTD hospitalization among infants

  Lab-confirmed RSV-positive LRTD hospitalization occurring ≤180 days after birth

  From birth through 6 months of age

Secondary Outcomes (2)

• RSV-associated severe LRTD hospitalization among infants

  From birth through 6 months of age

• RSV-associated LRTD hospitalization among infants, stratified by temporal and clinical characteristics

  From birth through 6 months of age

Study Arms (3)

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).

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).

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).

Biological: ABRYSVO

Interventions

ABRYSVO BIOLOGICAL

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).

Cases (Test Negative Design and Cohort Design); Controls (Test Negative Design); Ecologic Cohort (Ecologic Before-and-After Design)

Eligibility Criteria

• Age: 0 Years - 24 Months
• Sex: all
• Healthy Volunteers: No
• Age Groups: Child (0-17)
• Sampling Method: Probability Sample

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.

You may qualify if:

• 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.

You may not qualify if:

• 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).
• \. RSV positive cases ≤9 months of age from the TND study.
• 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.

Sponsors & Collaborators

• Pfizer: lead
• iTrials S.A.: collaborator

Study Sites (1)

Pfizer

Buenos Aires, Argentina

Location

Related Links

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

Biospecimen

Retention: NONE RETAINED

Standard of care RSV testing

MeSH Terms

Conditions

Respiratory Tract Diseases

Interventions

abrysvo

Study Officials

• Pfizer CT.gov Call Center

  Pfizer

  STUDY DIRECTOR

Study Design

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

Study Record Dates

• First Submitted: October 16, 2024
• First Posted: October 18, 2024
• Study Start: August 26, 2024
• Primary Completion (Estimated): October 1, 2026
• Study Completion (Estimated): October 1, 2026
• Last Updated: October 2, 2025

Record last verified: 2025-10

Data Sharing

• IPD Sharing: Will not share

Locations

AR (1)