FDA Approves Abrysvo: First Vaccine to Protect Infants from Potentially Life-Threatening RSV
In a milestone decision, the U.S. Food and Drug Administration (FDA) has granted its approval to Abrysvo (Respiratory Syncytial Virus Vaccine), marking the first-ever vaccine authorized for use in pregnant individuals to safeguard infants from lower respiratory tract disease (LRTD) caused by respiratory syncytial virus (RSV). This breakthrough vaccine targets infants from birth through 6 months of age and is administered through a single dose injection into the muscle.
The approval of Abrysvo is significant in addressing the risks associated with RSV, which is a highly contagious virus causing respiratory infections across all age groups. Infants are particularly vulnerable to severe diseases resulting from RSV, often requiring hospitalization. With this approval, healthcare providers and pregnant individuals now have an option to protect infants from this potentially life-threatening illness.
RSV is the leading cause of lower respiratory tract illness in infants worldwide, and its circulation follows a seasonal pattern, typically peaking during the winter months. While most cases of RSV in infants and young children manifest as cold-like symptoms, some can progress to more severe forms such as pneumonia and bronchiolitis (inflammation of small airway passages in the lungs). During the first year of life, infants and children face the highest risk of developing RSV-associated LRTD. In fact, RSV is known to be the primary cause of infant hospitalization in the United States.
The effectiveness and safety of Abrysvo for preventing LRTD and severe LRTD caused by RSV in infants were evaluated through ongoing international clinical studies. The results of one study, which included approximately 3,500 pregnant individuals who received Abrysvo and an equal number who received a placebo, indicated that this vaccine reduced the risk of severe LRTD by 81.8% within 90 days and by 69.4% within 180 days after birth. Another subgroup study, comprising pregnant individuals in the gestational age range of 32 to 36 weeks, revealed that Abrysvo reduced 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, the vaccine demonstrated a risk reduction of 57.3% for LRTD and 76.5% for severe LRTD, compared to the placebo.
Regarding safety, two studies involving a total of approximately 3,600 pregnant individuals who received Abrysvo and an equivalent number who received placebo were conducted. The most commonly reported side effects among pregnant individuals who received Abrysvo were pain at the injection site, headache, muscle pain, and nausea.
However, it is worth mentioning that a rare hypertensive disorder known as pre-eclampsia occurred in 1.8% of pregnant individuals who received Abrysvo, compared to 1.4% who received the placebo. Additionally, the safety studies revealed a higher incidence of low birth weight and jaundice in infants born to pregnant individuals who received Abrysvo compared to those who received the placebo.
As a precautionary measure, the Prescribing Information for Abrysvo now contains a warning about a numerical imbalance in preterm births among vaccine recipients (5.7%) compared to those who received the placebo (4.7%). However, the available data is insufficient to establish or exclude a causal relationship between preterm birth and Abrysvo. Consequently, healthcare providers are advised to administer Abrysvo from 32 through 36 weeks of gestational age to avoid potential risks associated with preterm birth. It is essential to note that individuals at a higher risk of preterm birth were largely excluded from clinical studies involving Abrysvo.
To ensure ongoing monitoring of any serious risks related to preterm birth and hypertensive disorders of pregnancy, including pre-eclampsia, the FDA has mandated postmarketing studies for the manufacturer of Abrysvo, Pfizer Inc.
The FDA’s decision to approve Abrysvo for use in pregnant individuals marks a significant achievement in protecting infants from RSV-related illnesses. By providing healthcare providers and expecting parents with an additional preventive measure, this vaccine offers a valuable tool in reducing the risk of severe respiratory diseases in vulnerable infants.
