The U.S. Food and Drug Administration (FDA) on Monday approved a new preventive treatment to defend babies and toddlers from the common and sometimes dangerous respiratory syncytial virus (RSV). The injectable drug, called Beyfortus (nirsevimab-alip), is designed for all babies entering their first RSV season, and for children up to 2 years old who remain vulnerable to severe RSV disease through their second RSV season.
“RSV can cause serious disease in infants and some children and results in a large number of emergency department and physician office visits each year,” said John Farley, MD, MPH, director of the Office of Infectious Diseases in the FDA’s Center for Drug Evaluation and Research, in a statement.
The Centers for Disease Control and Prevention (CDC) estimates that RSV hospitalizes 58,000 to 80,000 children under age 5 every year. RSV is the leading cause of hospitalization for infants under age 1 in the United States, averaging 16 times higher than the annual rate for influenza.
Although RSV typically results in mild, cold-like symptoms in most infants and young children, some develop lower respiratory tract disease such as pneumonia and bronchiolitis (swelling of the small airway passages in the lungs). Premature infants and those with chronic lung disease or significant congenital heart disease are at highest risk from RSV.
“Every year we have babies [with RSV] filling up our hospital beds who are blue because they can’t breathe, they’re coughing and need oxygen — some need to be put on ventilators,” says Yvonne Maldonado, MD, chief of the division of pediatric infectious diseases at Stanford University School of Medicine in Palo Alto, California. “This drug is a real opportunity to keep literally thousands of kids out of the hospital every single year for decades to come, so families won’t have to suffer through all that.”
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How Does the New RSV Treatment Work?
Developed by AstraZeneca and Sanofi, Beyfortus is a type of protein called a monoclonal antibody. It works by attaching to a protein called F protein on the surface of the virus. When the drug is attached to this protein, the virus becomes unable to enter the body’s cells, especially cells in the lungs, according to the European Medicines Agency.
Although Beyfortus prevents illness, Dr. Maldonado emphasizes that it is not a vaccine. “A vaccine causes the body to develop its own long-term antibodies,” she says. A vaccine prompts your immune system to “learn” about the virus so it can build longer-lasting defenses that can fight future infections.
A monoclonal antibody works differently. According to AstraZeneca, these lab-made antibodies mimic natural antibodies. Usually a vaccine takes a few weeks to generate an immune response, but a monoclonal antibody goes into action almost immediately.
In general, vaccines offer lasting long-term protection, while monoclonal antibody treatments are effective for a few months. In clinical trials, a single dose of Beyfortus, administered as a single injection, protected against RSV for about five months, the duration of a typical RSV season (typically the fall to the end of spring).
Maldonado adds that the virus doesn’t appear to significantly mutate, so it’s unlikely the formula for the treatment formula will have to be changed over time.
The FDA has already approved another monoclonal antibody injection called Synagis (palivizumab), but that is only for high-risk infants who were born severely premature.
How Well Does the New RSV Treatment Work and When Will It Be Available?
So far, AstraZeneca says, clinical trials with infants have demonstrated that Beyfortus lowers the incidence of RSV-caused lower respiratory tract disease (such as bronchiolitis or pneumonia) by 70 to 75 percent compared with placebo.
Study has also shown the shot to be safe and easy to administer, according to Maldonado.
The drug will not be available to the public until after an advisory panel for the CDC gathers to determine guidelines on how the medication should be administered and who should receive it. Maldonado expects the meeting to be held before the end of August.
Is There a Vaccine to Protect Babies Against RSV?
A vaccine that can prevent RSV in babies is in the pipeline. In May, an FDA advisory group voted in support of a vaccine for women in their second or third trimesters of pregnancy to defend against lower respiratory tract infection and severe disease in young children up to six months old. A decision by the FDA is expected in August, according to drug manufacturer Pfizer.
Maldonado anticipates that CDC advisors will be considering questions on how these forthcoming RSV vaccines and the just-approved monoclonal antibodies may be offered. Should children get both types of shots? If not, how can parents decide what is best to protect their infant?
“My sense is that there’s going to be some kind of a compromise where people are going to be encouraged to do what they think is best for their own situation,” says Maldonado. “I would encourage pregnant women to get the vaccine just like we vaccinated pregnant women against pertussis or whooping cough to prevent their babies from getting it. Then the question is, if the baby’s already highly protected from the mother’s vaccine for the first six months of age, how much more benefit are they going to get from giving the baby the Beyfortus shot in the first month or so of life? That's all going to have to be worked out over time.”