The FDA has approved two options to protect infants against RSV (respiratory syncytial virus) this season. One is a vaccine administered during pregnancy, and the other is a monoclonal antibody shot given to infants after birth. Here’s what we know about these so far. This page will primarily focus on the infant shot for our patients as the maternal vaccine falls within the domain of your maternal healthcare provider.
What is RSV? RSV, or Respiratory Syncytial Virus, is the most common cause of lower respiratory tract infection in infants and the leading cause of respiratory-related hospitalizations in young children world-wide. Such small airways have a difficult time managing the huge amounts of inflammation and mucus that accompany this infection, frequently leading to respiratory distress. It typically presents with nasal discharge, coughing, wheezing/difficulty breathing, and may be accompanied by fever, vomiting, and poor feeding. Virtually all children in the US will catch RSV at least once by 2 years of age. Around 20 percent develop wheezing during the first year of life, and 2 to 3 percent require hospitalization.
Maternal vaccine: Briefly, while there are some potential risks to consider, the data indicate it is overall effective and generally well-tolerated. It shouldn’t interfere with the infant shot, as they work in different ways, but we’re still awaiting further recommendations on this from the CDC Advisory Committee on Immunization Practices. You can read about the maternal vaccine here and here, and again we recommend you discuss this with your OB/GYN and/or midwife.
Infant shot (nirsevimab): We recommend this for all eligible infants in our practice. It’s not technically a vaccine, it's a "monoclonal antibody" (see below for the difference if you are interested). It was shown to reduce the risk of medically attended RSV by 75% in clinical trials. It is recommended by the American Academy of Pediatrics (AAP) for all infants younger than 8 months born during or entering their first RSV season (and some high risk older infants). That’s typically October through March.
We were pleased to see that clinical trials showed an excellent safety profile. There were the typical rash and injection site reactions you'd expect, while more significant issues such as serious allergic reactions were rare. We actually have plenty of experience with RSV monoclonal antibody shots because a similar product, palivizumab, has been in use within pediatrics since 1998 with an excellent safety record. It was only reserved for high risk infants because it was so expensive and had to be administered every month, but it was otherwise great. So the new shot, Nirsevimab, is about making this more financially viable and easier to administer with a single shot so all babies can benefit from it.
We plan to have this available for eligible infants at our clinic, barring issues with insurance coverage. Newborns should ideally get it at the hospital before discharge, otherwise they can get it at our clinic in the first week of life. For most other babies, they can get it during a well check with us (it can be administered along with routine childhood vaccines), but if there isn't a well check that aligns with the start of the RSV season (~October), families can schedule a shot-only visit for it.
What is a monoclonal antibody? Vaccines work by administering an "antigen", which could for example be a piece of a virus or a weakened strain of a virus. This enables the patient's immune system to be able to recognize what the virus looks like and start making antibodies to give them a leg up when they eventually encounter the virus. The other approach is to simply administer pre-made antibodies directly, skipping the antigen part.
There are several advantages of this. For one, it takes effect immediately because you don't need to wait for the patient to make antibodies. This is great for protecting newborns from illnesses like RSV where the greatest risk occurs before their body would have had enough time to develop protection from a vaccine. You also don't need to worry about a patient's ability to make adequate antibodies if they are immunocompromised, or the virus's antigen triggering some type of undesired immune reaction.
There are also some disadvantages. For one, it's substantially more expensive to produce. Some vaccines are available for as little as 20 bucks, whereas monoclonal antibody shots can exceed a thousand dollars per shot. The second major drawback is that the effect is not as lasting as a vaccine. Antibodies only last for around 5 to 6 months before they're gone for good. Vaccines are an active process ("teach a person how to fish"), whereas monoclonal antibody shots are passive ("give a person a fish"). So for most conditions, where the risk is usually ongoing, vaccines are better suited. They're effective, long-lasting, and far more affordable. But if you need immediate short-term protection, such as with RSV, monoclonal antibodies are an excellent choice as long as they’re able to get the costs down to where it is feasible.