First RSV Vaccine for Babies Gets FDA Approval

The U.S. Food and Drug Administration (FDA) has approved the world’s first vaccine to protect newborns and young infants against RSV (respiratory syncytial virus) — a common and highly contagious respiratory virus that can sometimes lead to severe and even life-threatening infections.

Abrysvo is a maternal vaccine, meaning it is administered to pregnant women, who then develop and pass on protective antibodies to their babies. Administered in a single shot at 32 to 36 weeks of pregnancy, the vaccine significantly protects children from birth to age 6 months, when they are at highest risk of RSV-related complications.

While RSV most often produces cold-like symptoms, it can sometimes cause pneumonia and bronchiolitis (swelling of the small airway passages in the lungs).

Approval for this Pfizer vaccine comes just a few months after the FDA and the Centers for Disease Control and Prevention (CDC) cleared the shot for older adults, age 60 and higher, who are also especially vulnerable to serious illness from the virus.

Pending review and endorsement by the CDC, the vaccine should be available in advance of the upcoming RSV season, which typically begins in the fall and continues through the winter.

Why Do Babies Need an RSV Vaccine?

RSV is the No. 1 cause of lower respiratory tract illness in infants and toddlers.

Worldwide, an estimated 6.6 million babies younger than 6 months get RSV annually, with about 45,000 dying each year from complications associated with the infection. In the United States as many as 300 children younger than age 5 die per year, and up to 80,000 are hospitalized.

Since RSV was discovered in 1956, scientists have been trying to develop an effective way to protect vulnerable young children.

Vaccine Provides Significant Protection Against a Devastating Illness

Late-stage clinical trials published in The New England Journal of Medicine showed that infants born to women who had received the vaccine had an 82 percent lower risk of developing severe lower respiratory tract illness within 90 days after birth and a 69.4 percent lower risk within 180 days after birth.

The findings were based on 3,570 babies whose mothers were inoculated and 3,558 babies whose mother received a placebo.

Elizabeth Schlaudecker, MD, principal investigator for the Pfizer maternal RSV vaccine clinical trial at Cincinnati Children’s Hospital and medical director of the hospital’s division of infectious diseases, notes that the vaccine was effective against less severe infections as well.

In a subgroup of pregnant individuals (1,500 who received Abrysvo and 1,500 who received placebo), the vaccine lowered the risk of any kind of RSV illness by 57.3 percent and cut the risk of severe disease by 76.5 percent within 180 days after birth.

“RSV is one of the most feared and most severe diseases in infants around the world, and we now have a very safe and effective way to protect them even before they’re born,” says Dr. Schlaudecker. “And we know that vaccinating pregnant women is a very easy and safe way to provide that protection.”

Is the RSV Vaccine for Babies Safe?

During the late-stage clinical trial, researchers detected no significant safety issues in mothers or children up to two years of age. The incidences of side effects reported in mothers within one month of injection and infants within one month of birth were similar in the vaccine group and placebo group.

Even so, some health officials expressed concern over premature births linked to vaccination. Acording to a May press release from Pfizer, the FDA’s Vaccines and Related Biological Products Advisory Committee (VRBPAC) voted a unanimous 14 to 0 on effectiveness, but the vote was 10 to 4 on safety, in part due to slightly higher rate of premature births in the vaccine group (5.7 percent) versus the control group (4.7 percent).

“There was some concern about potential for risk for prematurity in babies whose mothers got the vaccine even though it wasn’t a statistical difference between the placebo,” says Yvonne Maldonado, MD, a professor of global health and infectious diseases at Stanford University in California, who was not involved in the research. “It’s always about risk and benefit, and I see more significant risks of severe RSV in young babies versus potential risks of prematurity.”

Although not commonly reported, a dangerous hypertensive disorder, known as preeclampsia, occurred in 1.8 percent of pregnant individuals who received Abrysvo compared with 1.4 percent of pregnant individuals who received placebo. Jaundice in infants born to Abrysvo recipients also occurred at a higher rate.

Dr. Maldonado says that these concerns are likely to be addressed as the CDC develops RSV vaccination guidelines.

There Are Now 2 Ways to Protect Babies Against RSV

Another issue that the CDC will have to decide on is how to integrate the use of the RSV vaccine along with Beyfortus (nirsevimab), a newly approved medication given directly to infants as a shot to protect against RSV.

Beyfortus, a monoclonal antibody treatment developed by Sanofi and AstraZeneca, has been shown to reduce the risk of both hospitalizations and healthcare visits for RSV in infants by about 80 percent, according to the CDC. The health agency already recommends one dose of nirsevimab for all infants younger than 8 months, born during or entering their first RSV season.

“It’s almost an embarrassment of riches to have all of these potential choices to prevent this potentially devastating disease,” says Maldonado. “This year is going to be a learning curve for us all on how we implement these treatments.”

Schlaudecker imagines that the CDC might recommend a plan that involves a combination of the vaccine and the monoclonal antibody.

“We know that maternal vaccination protection starts to wane after you get past that first six months or so, but we will have the ability to give some extra protection to kids who have some extra high risk conditions,” she says.

Which Children Are at Highest Risk From RSV?

According to the CDC, children at greatest risk for severe illness from RSV include premature infants and children who are 12 months or younger, especially those who are 6 months old and younger.

Other highly vulnerable children include those younger than 2 with chronic lung disease or congenital (present from birth) heart disease, those with weakened immune systems, and those with neuromuscular disorders (which may cause difficulty swallowing or clearing mucus, for instance).