Real-world use affirms RSVpreF efficacy at preventing LRTD in infants

Maternal immunization with the bivalent respiratory syncytial virus (RSV) prefusion F vaccine (RSVpreF) helps lower the incidence of RSV-related lower respiratory tract disease (LRTD) and severe LRTD leading to hospitalization among infants from birth through age 6 months, according to real-world data from the BERNI study.

BERNI was a retrospective case-control study conducted during the 2024 RSV season in 12 hospitals across Argentina, the first country to implement a national maternal immunization programme with RSVpreF. Cases included infants born to women who received RSVpreF between 32^+0/7 weeks and 36^+6/7 weeks of gestation or 14 days or more before delivery.

The primary outcome was vaccine effectiveness against RSV-associated LRTD requiring hospitalization, while the key secondary outcome was RSV-associated severe LRTD requiring hospitalization.

A total of 505 infants were included in the primary effectiveness analysis, including 286 cases and 219 controls. Of these, 51 (18 percent) cases and 109 (50 percent) controls were born to women who received RSVpreF during pregnancy.

The vaccine demonstrated substantial effectiveness against RSV-associated LRTD requiring hospitalization—at 78.6 percent (95 percent confidence interval [CI], 62.1–87.9) from birth to 3 months of age and at 71.3 percent (95 percent CI, 53.3–82.3) from birth to 6 months of age.

Vaccine effectiveness against RSV-associated severe LRTD leading to hospitalization was 76.9 percent (95 percent CI, 45.0–90.3) from birth to age 6 months.

Three RSV-associated in-hospital deaths were documented, all of which were infants whose mothers did not receive RSVpreF during pregnancy.