Real-world effectiveness of bivalent prefusional bivalent vaccine F (RSVpreF) during pregnancy to prevent hospitalization for Respiratory Syncytial Virus (RSV)-associated acute lower respiratory infection (ALRI) in infants from birth to 6 months of age: results of RSV season 2024 from a multicenter case-control test-negative study conducted in Argentina.
In December 2023, Argentina became one of the first countries in the world to incorporate RSVpreF vaccine into the National Immunization Schedule. As of March 2024, maternal immunization with RSVpreF was implemented nationwide as the main strategy to reduce the burden of RSV-related diseases in infants. RSV is the leading cause of bronchiolitis, an acute respiratory infection that is most prevalent during the fall and winter months and mainly affects children under one year of age.
A collaborative study was designed by iTrials-Equipo Ciencia, the Health Policy and Equity Innovation Hub of the Universidad de San Martín and Pfizer, with funding provided by the latter. Its objective was to estimate the effectiveness of the RSVpreF vaccine (EV) in preventing hospitalizations for RSV-associated ARIB and severe ARIB in infants under six months of age during the first RSV season after implementation of the vaccination program.
The BERNI study (Real World Impact and Effectiveness of ABRYSVO™ Vaccination During Pregnancy Against RSV Illness in Infants)* is a multicenter, retrospective, case-control negative study conducted between April and September 2024 in 12 hospitals, including public, private and social security centers in six provinces of Argentina. Data were collected from medical records, epidemiological surveillance and hospital statistics. The study included infants under six months of age hospitalized for ARIB and tested for RSV.
VSR season 2024 results
The BERNI study included 505 infants (286 RSV-positive cases and 219 RSV-negative controls). The main findings included: Vaccine effectiveness (VE):
- Prevention of hospitalized ARI in infants aged 0 to 3 months: 72.7% (95%CI 60.0-81.4).
- Prevention of hospitalized ARI in infants aged 0 to 6 months: 68.0% (95%CI 56.2-76.6).
- Prevention of severe hospitalized ARI in infants aged 0 to 6 months: 73.9% (95%CI 53.2-85.4).
RSV-associated deaths
Three deaths due to RSV-associated ARIB were recorded, all in infants born to mothers who did not receive RSVpreF vaccine during pregnancy.
Conclusions
These results from the 2024 RSV season in Argentina demonstrate the high effectiveness of RSVpreF in preventing hospitalizations for RSV-associated ARI and severe ARI during the first six months of life. This real-world evidence from the first season of the program confirms and supports the findings of the Phase 3 clinical trial. An article with the full results of the study is in preparation.
The generation of local evidence on the effectiveness of public health strategies is essential for decision making. These results are fundamental to strengthen confidence among health professionals in recommending the vaccine, as well as among pregnant women to demand it, thus promoting a positive impact on community health. This is why the participating technical and scientific teams consider it a priority to share these findings in real time to support the effective implementation of health policies. These efforts are intended to benefit the Argentine population during the upcoming RSV seasons, while providing evidence to other countries evaluating the adoption of this preventive strategy against RSV-associated ARI in infants. In this context, the introduction of this vaccine represents a pioneering advance in the reduction of hospitalizations and severe respiratory infections during the first months of life.
Gonzalo Perez
iTrials / Science Team
Analía Rearte
Hub of Innovation in Health Policies and Equity, UNSAM
*Antonio BERNI, was one of the most outstanding Argentine painters. A recognized exponent of New Realism in Latin America, his work is characterized by a strong social and political commitment, often reflecting the struggles and challenges faced by the most vulnerable people, including children. His most recognized character was Juanito Laguna, the protagonist of this painting (Detail of Juanito dormido, 1974).
