The FDA approved a new RSV drug for babies and young children. Here's what parents need to know.

The Food and Drug Administration (FDA) has approved the drug Beyfortus for the prevention of respiratory syncytial virus (RSV) in babies and toddlers.

This comes on the heels of the FDA approving Arexvy for adults 60 and older back in May, which made it the first-ever vaccine for RSV. The news is being hailed by the medical community as a huge deal since young children — and older adults — are at high risk of serious complications from RSV.

Here's what you need to know about the latest RSV drug.

Why is RSV prevention so important?

RSV was discovered in 1956 and is one of the most common causes of childhood illness, according to the Centers for Disease Control and Prevention (CDC). The virus causes common-cold-like symptoms in most people, but it can also cause serious complications like bronchiolitis — an inflammation of the small airways in the lung — and pneumonia, an infection of the lungs. That's more common in premature infants, babies 6 months and younger, children under 2 with chronic lung disease or congenital heart disease, children with suppressed immune systems and children with neuromuscular disorders, the CDC says.

Up to 80,000 children under 5 years old are hospitalized due to RSV infection each year in the U.S., according to the CDC.

Adults can get RSV too. Like kids, most adults who get the virus have mild symptoms, like a runny nose, cough, headache, fatigue and fever, per the CDC. But some adults can develop more severe illness like pneumonia — that's especially true of adults age 65 and up, those with chronic lung or heart disease and adults with weakened immune systems, the CDC says.

"People at the extremes of life are the ones at highest risk of hospitalization and bad outcomes with RSV," Dr. Thomas Russo, an infectious disease expert at the University at Buffalo in New York, tells Yahoo Life.

While most people who get RSV do just fine, it can also be deadly, making RSV drugs and vaccines a big deal. Dr. Amesh Adalja, a senior scholar at the Johns Hopkins Center for Health Security, tells Yahoo Life that there was "a real clinical need for an adult RSV vaccine," which is why pharmaceutical companies "pursued that indication first." But as Russo previously told Yahoo Life, it's "critically important" to have drugs that can protect the pediatric age group from RSV.

How is the RSV drug for children different from the one for adults?

Unlike Arexvy for older adults, Beyfortus is a preventive drug — not a vaccine.

The medication delivers long-acting antibodies, in a process known as passive immunity, so it doesn't require the activation of the immune system to develop antibodies to RSV, according to Sanofi, one of the drug's creators.

Who is the RSV drug for?

Beyfortus is approved for infants born during or entering their first RSV season, and for children up to 24 months old who are vulnerable to severe RSV disease through their second RSV season, according to the FDA. RSV season typically starts during the fall and peaks in the winter.

The drug, which was jointly created by Sanofi and AstraZeneca, is given as a single injection either before or during RSV season in order to provide protection during that season, according to the FDA. The most common side effects of Beyfortus are rash and injection site reactions.

Three clinical trials found that Beyfortus reduces the risk of RSV in infants and children under 2 years old by 70 to 75%. Beyfortus is expected to be available in the U.S. before the upcoming 2023-2024 RSV season, according to AstraZeneca.

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