Bronchiolitis is a viral lower respiratory tract infection, caused in 50 to 80% of cases
by the respiratory syncytial virus (RSV).
Although generally mild, RSV bronchiolitis remains the leading cause of infant
hospitalizations for acute respiratory distress in Europe. In France, nearly 30% of
children under two years of age are affected annually, representing approximately 480,000
cases. RSV bronchiolitis accounts for 2 to 3% of hospital admissions among infants under
one year each winter. These situations place a significant burden on pediatric intensive
care units and emergency departments, impacting the delivery of care for other pediatric
patients and raising concerns among parent and families.
Until September 2023, RSV lower respiratory tract infection prevention strategies in
infants in France were limited to non-pharmacological barrier measures, with a monthly
injection of the monoclonal antibody palivizumab (Synagis®) recommended among high-risk
infants, particularly those born preterm before 35 weeks of gestation.
At the end of 2023, a new monoclonal antibody, nirsevimab (Beyfortus®), indicated for
passive immunization in the general infant population, received marketing authorization.
Administered as a single dose to neonates (from birth) and infants during their first RSV
season, nirsevimab demonstrated an estimated efficacy of 76% to 83% in preventing severe
RSV bronchiolitis during the 2023-2024 epidemic in France. At the same time, the RSV
vaccine Abrysvo® (Pfizer) became available in France since September 2024, following
European marketing authorization in August 2023. Administered during the third trimester
of pregnancy, this maternal immunization strategy aims to confer passive immunity to
neonates (from birth up to six months of age) through transplacental transfer of
RSV-specific maternal antibodies.
For the 2024-2025 RSV season, the national prevention strategy for RSV-related
respiratory infections in infants is based on general non-pharmacological measures and,
between September 15, 2024, and January 31, 2025, on maternal vaccination (administered
between 32 and 36 weeks of gestation) and/or direct administration of nirsevimab to
neonates.
To date, no population-based data are available in France regarding maternal adherence to
the current RSV prevention strategy for respiratory syncytial virus (RSV) infections in
infants. The acceptability of maternal RSV vaccination remains unknown, as well as the
factors associated with the choice between the two recommended strategies and the reasons
given by pregnant women for their decision.
The objective of this study is to assess, in population, the adherence of pregnant women
to the current RSV infection prevention strategy for infants in France, which has not yet
been studied. The study will focus on the method most commonly chosen by women (maternal
vaccination with Abrysvo® during pregnancy or administration of nirsevimab (Beyfortus®)
to their neonates), aiming to identify the factors associated with the choice of one
strategy over the other and to describe the main reasons women give for their decision to
either follow or not follow one of the prevention strategies.
