The vaccine, known as Abrysvo, can be given between weeks 32 and 36 of pregnancy and is designed to protect infants from the virus from birth to 6 months of age.
Administered as a single-dose, intramuscular injection, the FDA approved Abrysvo at the end of May for the prevention of lower respiratory tract illness caused by RSV in people aged 60 years and older.
However, “RSV is a common cause of illness in children, and infants are among those at highest risk for severe disease, which can lead to hospitalization,” Peter Marks, MD, PhD, director of the FDA’s Center for Biologics Evaluation and Research, pointed out in a news release. “This approval provides an option for health care providers and pregnant individuals to protect infants from this potentially life-threatening disease.”
Most children are infected with the contagious virus at least once by the time they reach age 2 years. Very young children are at particular risk of severe complications, such as pneumonia or bronchitis, and in clinical trials, the new vaccine reduced that risk by up to 82%.
Before the vaccine became available, up to 3% of infants infected with RSV needed to be hospitalized, according to the Centers for Disease Control and Prevention. In the hospital, treatment typically includes oxygen, intravenous fluids, and mechanical ventilation.
RSV often causes common cold symptoms, but the virus poses the risk of severe complications that can lead to death among young children and older people. The CDC estimates 100-300 deaths of children younger than 5 years and 6,000-10,000 deaths of people aged 65 years and older are linked to RSV annually.
This is also the first year that an antibody shot is available to be given after birth to prevent severe RSV in infants younger than 1 year.
In its approval announcement, the FDA pointed out that preeclampsia occurred in 1.8% of pregnancies after Abrysvo, compared with 1.4% of those who received placebo. The FDA also reported that, in infants, low birth weight and jaundice occurred at a higher rate among the pregnant Abrysvo recipients, compared with the placebo group.
Studies have also shown that pregnant vaccine recipients experienced preterm birth at a rate of 5.7%, compared with a rate of 4.7% among those who received placebo. The FDA called the difference “a numerical imbalance” but said in the approval announcement that a “causal relationship” could not be established.
The FDA also noted that people already at high risk of preterm birth were excluded from clinical trials and that Pfizer must conduct ongoing studies to monitor the risk of preeclampsia as well as preterm birth.
A version of this article first appeared on Medscape.com.