The new RSV monoclonal antibody
I have received many requests to talk about Beyfortus, which is the new monoclonal antibody against RSV that has just been approved by the FDA.
There’s already a lot of confusion about Beyfortus - and a lot of fear-mongering as well.
So lets sort out fact from melodrama.
First, its not a vaccine!
Beyfortus (nirsevimab-alip) is a new option that provides protection against RSV for babies. It is injectable, and I think there have been other RSV vaccines in the news recently (for the elderly and pregnant among us), so this confusion is understandable.
So one more time, let me clarify: Beyfortus is not a vaccine. It is a monoclonal antibody. Think of it as a medication.
What is RSV?
RSV is an infection that most children have caught and recovered from by the time they turn 2y. For older children, it often presents as a cold or cough. But for younger infants, who have less reserve and smaller airways, RSV infection can be very serious. About 1-3% of children under 1y are hospitalized due to RSV every year.
What is a monoclonal antibody?
A monoclonal antibody is a medication that essentially contains antibodies that look like the antibodies our own bodies make when encountering an infection (or immunization).
Basically, instead of forcing the body to make its own army to fight RSV (which relies on being exposed), you are providing the soldiers so that they’re there and ready to work if RSV does make an appearance.
More about Beyfortus
The research is, quite frankly, very exciting. So far there have been 3 trials that support the use of Beyfortus as an effective prevention measure against severe RSV-related illness (in preterm/term infants and in young toddlers) and reiterate its safety.
What does the data actually show?
Two large scale RCT trials confirmed that Beyfortus causes a 70-75% reduction in serious RSV illness and a 60-80% decrease in RSV hospitalizations in both term and preterm infants compared to placebo.
A third trial looked at its effect in toddlers with congenital heart disease, a population that is particularly susceptible to severe RSV disease. Beyfortus showed efficacy in that group as well.
There has been a lot of fear-mongering online about the side effects. The truth is, these were rare (and mild) - ranging from fever, injection site reactions and rash. Nothing overly surprising. There were some infant fatalities in the trials, but these have been investigated and the cause is thought to be unrelated to the antibody. For example, in this study (PMID 32726528), deaths in the Nirsevimab group were a result of other known infections (such as sepsis or meningitis), and undiagnosed cardiac disease. In this study (PMID: 35235726), infant fatalities were also thought to be due to unrelated infections (GI) or underlying chronic conditions.
It is also worth knowing that Beyfortus was approved in Europe a year ago.
We already use a different monoclonal antibody for RSV prevention in the highest risk babies.
Synagis (Palivizumab) is an RSV-specific monoclonal antibody which is extremely expensive. Pediatricians spend a lot of time arguing with insurance companies about which babies qualify for it — it is usually reserved for only the highest risk infants due to its cost.
One difference between Synagis and Beyfortus is the duration of effect. Synagis must be given every month during RSV season because its effect doesn’t last as long in the body. This is why Beyfortus is such a game changer — it offers several months of protection from a single dose.
What else to know:
Keep in mind that Beyfortus is PREVENTIVE. It is not an RSV treatment. The role it plays is to decrease the severity of illness, so you need to have it on board before exposure.
The recommendations:
Beyfortus has been recommended for all infants under 8mo, as well as high risk infants between 8-19mo entering their second RSV season (for example, infants who are immune compromised or have pre-existing lung disease - the cdc has more here about higher risk conditions).
Note that per the FDA, Beyfortus shouldn’t be given to those with a history of serious allergic reactions, or those with concerns of “clinically significant bleeding disorders”. As always, talk to your doctor if you are concerned.
Availability
Beyfortus availability is a little more tricky. The American Academy of Pediatrics made a statement supporting its use a couple of weeks ago and is urging a strategy to make sure that there is equitable access to Beyfortus across the country.
At this time, pediatrician offices are still waiting on more information regarding insurance coverage, as well as when they can receive and start administering it, although Sanofi claims that it will be available soon.
For pediatricians, RSV is a scary disease because of how quickly infants who have it can deteriorate. I think that Beyfortus may well be a game changer for infant health.
