The U.S. Food and Drug Administration (FDA) has granted approval for Abrysvo (Respiratory Syncytial Virus Vaccine), marking a significant milestone as the first vaccine authorized for use in pregnant individuals to prevent lower respiratory tract disease (LRTD) and severe LRTD induced by respiratory syncytial virus (RSV) in infants from birth through 6 months of age.
Abrysvo’s approved usage is between 32 and 36 weeks of gestational age. Administered via a single muscle injection, Abrysvo received FDA approval in May for preventing LRTD caused by RSV in individuals aged 60 and older.
Dr. Peter Marks, Director of the FDA’s Center for Biologics Evaluation and Research, emphasized the importance of this approval, stating, “This approval provides an option for healthcare providers and pregnant individuals to protect infants from this potentially life-threatening disease.”
RSV is a highly contagious virus responsible for respiratory infections across all age groups and is the leading cause of lower respiratory tract illness in infants globally. RSV activity is typically seasonal, peaking in the winter months, particularly in children.
While RSV often manifests as mild cold-like symptoms in infants and young children, it can progress to severe LRTD, including pneumonia and bronchiolitis. Infants and children face the highest risk of RSV-associated LRTD during their first year of life. In the U.S., RSV ranks as the leading cause of infant hospitalization. The approval of Abrysvo’s safety and effectiveness for pregnant individuals seeking to prevent LRTD and severe LRTD caused by RSV in infants was based on ongoing randomized, placebo-controlled international clinical studies.
One such clinical study assessed Abrysvo’s effectiveness in preventing LRTD and severe LRTD caused by RSV in infants born to vaccinated pregnant individuals. Among approximately 3,500 vaccinated pregnant individuals compared to the same number receiving a placebo, Abrysvo reduced the risk of severe LRTD by 81.8% within 90 days after birth and by 69.4% within 180 days after birth.
In a subgroup of pregnant individuals aged 32 through 36 weeks, of which around 1,500 received Abrysvo and 1,500 received a placebo, Abrysvo decreased the risk of LRTD by 34.7% and severe LRTD by 91.1% within 90 days after birth, compared to the placebo. Within 180 days after birth, Abrysvo reduced the risk of LRTD by 57.3% and severe LRTD by 76.5%, also compared to the placebo.
The safety of Abrysvo was evaluated in two separate studies involving pregnant individuals. One study included approximately 3,600 participants receiving Abrysvo and 3,600 receiving a placebo, while the second study involved around 100 individuals receiving Abrysvo and 100 receiving a placebo. Common side effects reported by pregnant individuals receiving Abrysvo included pain at the injection site, headache, muscle pain, and nausea.
Although not frequently reported, an alarming hypertensive disorder called pre-eclampsia occurred in 1.8% of pregnant Abrysvo recipients compared to 1.4% of those who received a placebo. Safety studies also revealed a higher incidence of low birth weight and jaundice in infants born to pregnant Abrysvo recipients than those born to pregnant placebo recipients.
The Prescribing Information for Abrysvo includes a warning regarding a numerical imbalance in preterm births among Abrysvo recipients (5.7%) compared to those who received a placebo (4.7%). While the available data do not definitively establish or rule out a causal link between preterm birth and Abrysvo, healthcare providers are advised to administer Abrysvo in pregnant individuals between 32 and 36 weeks of gestational age to mitigate the potential risk of preterm birth in pregnancies before 32 weeks.
Clinical studies typically excluded pregnant individuals at increased risk of preterm birth. The FDA is mandating postmarketing studies to further investigate the potentially serious risk of preterm birth and to assess hypertensive disorders during pregnancy, including pre-eclampsia.