Beyfortus vs. Synagis for RSV Prevention in Children: 6 Differences Parents Should Know

During the fall and winter months, a variety of seasonal illnesses circulate across the U.S. Influenza (the flu) is one that likely comes to mind. But many infants and young children experience their first respiratory syncytial virus (RSV) infection during this time, too.

Premature infants and certain high-risk children may be given Synagis (palivizumab) — a monthly injection that prevents serious respiratory illness from RSV. However, more infants are eligible for Beyfortus (nirsevimab-alip), a long-acting shot that also prevents severe RSV.

Since RSV can be dangerous in infants and young children, it’s important to keep your child protected. So, what’s the difference between Beyfortus and Synagis? Below, we cover six key differences you should know.

1. Beyfortus is recommended more newborns and infants entering their first RSV season compared to Synagis

Beyfortus is recommended for most newborns and infants under 8 months old going into their first RSV season — as long as the mother didn’t receive an RSV vaccine during pregnancy (more on that below). A dose is also recommended for certain children ages 8 to 19 months who are entering their second RSV season. 

The CDC also recommends Synagis in certain situations, but for a smaller range of children. Below, we’ll cover the details of who should receive Beyfortus and Synagis.

Beyfortus eligibility

CDC recommendations for Beyfortus are as follows:

• Newborns and infants under 8 months old going into their first RSV season, unless the mother received an RSV vaccine (Abrysvo) during pregnancy and the baby was born at least 14 days later. In this case, Beyfortus isn’t usually needed.

• Certain children ages 8 to 19 months who are entering their second RSV season, such as those who are severely immunocompromised, have cystic fibrosis with severe lung disease, or low weight. American Indian and Alaska Native children should also receive Beyfortus if they meet the age criteria. 

For infants born during RSV season, a dose is typically given during the first week of life.

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It’s important to note that Beyfortus is FDA approved for a wider range of children than the CDC recommendations include. However, most pediatricians follow CDC recommendations when recommending Beyfortus.

Synagis eligibility

Synagis is only approved for certain infants and young children who are especially vulnerable to severe RSV. The American Academy of Pediatrics (AAP) recommends Synagis for the following children in their first year of life:

• Premature infants who were born before 29 weeks gestation

• Premature infants with chronic lung disease of prematurity, which is defined as being born before 32 weeks gestation and requiring oxygen for at least 28 days after birth

Synagis may also be recommended for infants in their first year of life with heart disease, lung disease, or neuromuscular disease. Synagis isn’t typically recommended after the first year of life except for certain children who are severely immunocompromised.

Note that Synagis is FDA approved for a wider range of children than the AAP recommends However, most healthcare professionals follow the AAP recommendations. Your child’s healthcare professional will decide whether Synagis is right for them based on their age, health, and RSV risk.

2. Beyfortus is given once per RSV season, while Synagis requires several doses

Protection from Beyfortus has been shown to last through 5 months, which means one dose should last an entire RSV season.

Synagis, on the other hand, doesn’t last as long in the body. Each dose lasts about 28 to 30 days, so your child will need to receive monthly doses for the duration of RSV season. Between the two, Beyfortus offers a more convenient option for parents since your child only needs one shot. 

3. Beyfortus and Synagis work in similar, but slightly different ways

Beyfortus and Synagis aren’t vaccines. They’re both monoclonal antibodies — lab-made proteins that attach to RSV and block it from entering and infecting cells. Unlike a vaccine, they don’t stimulate your child’s immune system.

Instead, Beyfortus and Synagis provide what’s called “passive immunity” against RSV. They give your child man-made antibodies (immune system proteins) that can quickly recognize and fight RSV. Your child can still get RSV, but they’re less likely to develop serious respiratory illness from the infection.

Although Beyfortus and Synagis work similarly, they do have slight differences, too.

Beyfortus and Synagis target different parts of RSV

Beyfortus and Synagis both target a protein (called the F protein) that helps RSV fuse with human cells to infect them. The F protein has two different forms with distinct shapes — preF (before fusing with a cell) and postF (after fusing with a cell).

Beyfortus works by binding to the preF form, which is the same target as the RSV vaccines, Abrysvo, Arexvy, and mRESVIA. The preF form is thought to produce the strongest protective effects against RSV. Synagis, however, binds to both the preF and postF forms. But this hasn’t been shown to make Synagis more effective than Beyfortus, which we'll discuss below.

4. Beyfortus increases RSV-fighting antibodies more than Synagis

One study of about 800 infants found that a single dose of Beyfortus provided higher levels of RSV-fighting antibodies compared to five monthly doses of Synagis. Additionally, these antibody levels were sustained for a longer amount of time with Beyfortus. These characteristics of Beyfortus may make it more effective than Synagis.

Additionally, research shows that Beyfortus and Synagis are similarly safe.

5. Beyfortus will be available through the Vaccines For Children program

Beyfortus isn’t a vaccine. But it’s a useful tool that can help keep infants and young children safe during RSV season. Because of this, a CDC expert panel voted to add Beyfortus to the Vaccines For Children (VFC) program. The VFC program helps provide vaccines and immunizations at no cost to children who meet certain criteria.

If your child is uninsured or underinsured, Medicaid-eligible, or American Indian or Alaska Native, they may qualify. If you need help finding a VFC provider, check out your state’s VFC provider locator.

Synagis isn’t part of the VFC program. However, there are ways to save on Synagis, which we’ll cover later on.

6. Beyfortus and Synagis may have different side effects

Beyfortus and Synagis side effects are generally mild. With both medications, injection site reactions such as pain, redness, or swelling can happen. Rash can also occur.

In studies of Synagis, some babies had a fever after receiving a dose. However, it was only about 2% more than babies receiving placebo (a shot with nothing in it).

More severe risks of Synagis and Beyfortus include allergic reactions. Additionally, increased bleeding can happen in children with conditions that cause bleeding or bruising. This is because intramuscular (IM) injections like Beyfortus and Synagis can cause bleeding at the injection site. This may be worse if your child has a condition that makes them more likely to bleed.

Overall, Synagis and Beyfortus cause minimal side effects. Talk to your healthcare professional if you’re concerned about the risks, and they can discuss the safety of these injections further.

How to save

Beyfortus’ list price is expected to be around $500. But if you have private health insurance, Beyfortus is likely covered by your insurance plan. This is a requirement of the Affordable Care Act. Still, it’s best to call your insurance company directly to check if Beyfortus is covered for your child.

Additionally, Beyfortus may be free for eligible children through the VFC program. This may include children with Medicaid or those who are uninsured or underinsured. Children who are American Indian or Alaskan Native are also eligible to receive Beyfortus for free through VFC. This directory can help you locate a vaccine provider near you.

Synagis may also be covered or partially covered by Medicaid or private insurance. In some cases, it may require a prior authorization. Additionally, people with private insurance may be able to use a copay card for Synagis to pay as little as $0 per dose, with up to $6,000 of savings per year.

However, Synagis isn’t available through the VFC program. 

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Written by:

Alyssa Billingsley, PharmD

Alyssa Billingsley, PharmD, is the director of pharmacy content for GoodRx. She has over a decade of experience as a pharmacist and has worked in clinical, academic, and administrative roles.

Reviewed by:

Patricia Pinto-Garcia, MD, MPH

Patricia Pinto-Garcia, MD, MPH, is a medical editor at GoodRx. She is a licensed, board-certified pediatrician with more than a decade of experience in academic medicine.

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