effectiveness of abrysvo® maternal respiratory syncytial virus (rsv) vaccine against rsv in infants in western pennsylvania

Conditions: Respiratory Syncytial Viruses

Summary: globally, respiratory syncytial virus (rsv) is the leading cause of lower respiratory tract disease (lrtd) in infants. pfizer has developed abrysvo-a bivalent rsv prefusion f protein-based vaccine (rsvpref) composed of two prefusion f proteins to protect against both rsv-a and rsv-b. in the united states, abrysvo has been approved and recommended for active immunization of pregnant individuals from 32 0/7 to 36 6/7 weeks' gestational age for the prevention of lrtd and severe lrtd caused by rsv in infants from birth through 6 months of age. to generate critical evidence to support vaccine policy and implementation, pfizer will collaborate with university of pittsburgh to study vaccine effectiveness (ve) of abrysvo vaccination during pregnancy against rsv-associated outcomes in infants. the study will take place in a real-world population in western pennsylvania over multiple seasons, beginning in the 2023-2024 season, and will use a test negative design (tnd approach). there will be no active enrollment of study participants, no direct contact with study participants, and no collection of any primary data outside of the standard of care (soc). this study will use a tnd to evaluate real-world ve of maternal abrysvo against rsv-associated outcomes in infants. additionally, we will describe rsv-associated medically-attended visits for infants exposed to abrysvo and beyfortus (monoclonal antibody (mab) administered to babies up to 24 months for protection against rsv).


Eligibility criteria:
population included in abyrsvo ve analyses: 1. infants ≤ 6 months (≤ 180 days) of age on the index date. 2. index date within the time period for data collection (approximately 01 october to 15 april in the 2023-2024 and 2024-2025 rsv seasons). 3. infants born at ≥32 weeks of gestation. 4. infants 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 the local vaccination season. 5. infant's electronic health record links to the maternal electronic health record. 6. hospitalized at a upmc facility during the rsv season (according to local hospital epidemiology ) with acute respiratory tract illness symptoms meeting the protocol-defined clinical case, and for whom rsv testing results from a specimen collected 10 days prior to hospital admission through 3 days after hospital admission are known. 7. ability to document maternal abrysvo receipt or not. population excluded from abyrsvo ve analyses: 1. infants who received any licensed or investigational rsv preventive product (e.g., palivizumab, beyfortus, active rsv vaccine (including investigational products or due to medication error) since birth. 2. born to birth parent for whom abrysvo vaccination status cannot be verified in the maternal electronic health record or pennsylvania immunization electronic registry system (piers) system. 3. infants who were born to an individual vaccinated with any other licensed or investigational rsv vaccine during pregnancy.