The respiratory virus season of 2022-2023 was bad. Real bad. I discussed this last November in a bleary-eyed post:
I have been a pediatrician since 2003, and generally aware of medical stuff since starting medical school in 1999, and I have never personally experienced a month like the one we are having. Prior to the pandemic-related lull over the past two seasons, RSV had always kept us busy. It is the most common reason for infants to be admitted to a hospital every year, after all. But I have never seen admissions come in at this pace, which has far surpassed any previous busy winter.
Though it wasn’t the only virus causing problems, the main culprit behind the surge of admissions last season was respiratory syncitial virus, commonly referred to as simply RSV. It’s incredibly prevalent and pediatric hospitalists like me take care of thousands of cases over a typical career. I go into some detail on the viral pathogen in this post:
In these younger children, RSV is the most common cause of lower respiratory tract infections and the most likely reason for them to be hospitalized. Hospitalization with RSV has been much more common than I bet most people realize, even before this season’s historic rates. Globally, roughly 4 out of every 1,000 children under 5 years become ill enough to need a hospital bed. If you focus on the highest risk groups, it gets much worse with 20 per 1,000 children less than 6 months and 60 per 1,000 premature infants being hospitalized every year.
Hospitalization is less likely in the United States, where the general nutritional status of children is more stable than in developing regions of Africa and Asia, for example, but it is still common. Here roughly 3 per 1,000 kids under 5 years are hospitalized. In our highest risk populations of infants less than 6 months, roughly 15 per 1,000 need an inpatient or PICU bed.
As the end of summer looms ominously in the far too near future, we are all gearing up for another rough fall and winter surge of respiratory admissions. Pediatricians and family docs are hopeful that it won’t be quite as bad this go around, however, given that a lot of kids will have some residual immunity left over from a year ago. Immunity to RSV doesn’t last long, but reinfection within a year or so might be less severe disease. There will still be plenty of vulnerable young infants enjoying their first (insert meaningful wintertime cultural event) and, even in a good year, RSV season can be pretty awful.
Good news, everyone!
On August 3rd, the Advisory Committee on Immunization Practices and the CDC voted unanimously in favor of recommending the use of a recently approved injection proven to reduce the risk of severe RSV disease in young children. And just this week, the American Academy of Pediatrics has come out with their recommendations for which young children should be the focus of the drug’s roll out. Nirsevimab (brand name Beyfortus), like palivizumab (Synagis) before it, is a monoclonal antibody* that provides passive immunity rather than a vaccine that induces the body to produce its own antibodies. But there are some important differences, primarily that palivizumab requires monthly injections, and, even more importantly, it just doesn’t work as well as we would like:
As detailed in the accompanying technical report, the benefit resulting from this drug is limited. Palivizumab prophylaxis has limited effect on RSV hospitalizations on a population basis, no measurable effect on mortality, and a minimal effect on subsequent wheezing.
While far from useless, and extremely safe, the AAP has recommended palivizumab only for infants born significantly premature and those born a bit further along with specific risk factors for severe disease. Nirsevimab, which is also remarkably safe, has on the other hand has been found to reduce the risk of medically attended (urgent care clinic, physician office, ER visit, hospitalization) RSV by 75% in clinical trials. Thus their recommendations for its use are much more broad:
The AAP recommends a single dose of nirsevimab for:
- All infants younger than 8 months born during or entering their first RSV season.
- Infants and children aged 8 through 19 months who are at increased risk of severe RSV disease and entering their second RSV season.
In an ideal scenario, nirsevimab will become available for all children who qualify for it this season and completely replace palivizumab (sorry Sobi) for those infants who would have received that drug. Unfortunately, that is unlikely to be the case as the logistics of it all are going to be complicated and expensive. There are several issues that will impede the roll out for this season:
- Pediatric practices will be busy dealing with the transition to a commercialized COVID-19 vaccine. Adding a new recommended medication that still lacks billing codes for its administration will result in these practices taking an intolerable financial hit, so they might wait until 2024-2025.
- Nirsevimab administration will likely require many pediatric practices to train staff or hire new staff in order to follow state guidelines. They might have to pay for and make room for additional storage capacity. They will have to pay**, up front, for the doses. And all of this has to be done knowing that there might be significant hesitancy from caregivers and that it may take up to a year for insurance payments to reach their bank accounts. Many practices could opt out.
- Many children rely on the Vaccines for Children program to receive recommended immunizations. Nirsevimab, though not a vaccine, will be included in the program. This is a really good thing but VFC-funded products take longer to reach children than those that are payed for privately. RSV will get to many of these kids before they have access to the shot.
There is reason for parents and pediatric healthcare providers to be excited when it comes to nirsevimab. I certainly am. I can’t imagine having another RSV season like the last one, though I fully realize that it might be just as bad in a few months. But I’m hopeful that all the bumps in the road will be smoothed out for 2024-2025. Then we will just have to focus on how to reassure caregivers, reduce the expected hesitancy to this new drug, and counteract the tidal wave of misinformation that is certainly heading our way.
*Nirsevimab specifically binds to the RSV fusion (F) protein, which is the site where the virus binds to cilliated cells that make up the bulk of our human respiratory epithelium.
**The cost of one dose for each child will likely be less than a tenth of palivizumab’s total seasonal cost, but will still likely cost a few hundred bucks. It will almost certainly be cost effective system wide but many families will not be able to afford it without assistance.