The beginning of respiratory virus season, a large part of which involves infections with respiratory syncitial virus (RSV), is right around the corner. The CDC is predicting that it will be about as bad for kids as it was last year, and perhaps even better. Last year wasn’t great, but it was definitely better than the train wreck that was 2022-2023. Those were rough times for pediatricians, particularly in hospitals in many regions around the country.
I wrote about my experience in the Boston area at the time here and here. Last year was still hard but much more manageable without the severe shortage of intensive care and hospital beds that had us managing critically ill babies in hallways at a community hospital with no PICU. As I discussed last summer here, pediatric healthcare providers and families with young children were excited about the prospect for better days ahead because of the roll out of a new medication that could prevent severe RSV in infants and high risk toddlers.
Nirsevimab (brand name Beyfortus) is an injection that contains antibodies against the F protein on the surface of the virus, rather than a vaccine that would encourage the body to make the antibody itself. That would work, and it does with the RSV vaccine recommended for pregnant people during RSV season and all people over 75 years, or 60 years if they have risk factors for severe disease or live in a nursing home. The F protein helps the RSV virus enter human cells, particularly in the lungs, which is why the shot was so promising as a prevention of severe disease.
Nirsevimab almost certainly reduced the severity of last year’s RSV season. Millions of doses were given out but there were huge issues with getting shots into arms. These ranged from expected logistical problems with a new drug that required staff training, space for refrigeration, and ironing out insurance coverage, but there was also the unexpected lack of supply when the manufacturers dropped the ball. Then, of course, there were difficulties with caregiver hesitancy and refusal, which varied from region to region in the usual ways. Florida, I’m talking about you.
Data from before the roll out looked really good, with an excellent safety profile and great efficacy at preventing RSV disease that required medical care. Preliminary data from after the roll out looked even better:
So what did they find? Ultimately 699 infants met criteria, 407 of which were positive for RSV and 292 of which weren’t. 1% of RSV positive patients had received Beyfortus compared to 18% of the RSV negative patients. Using multivariable logistic regression models (some kind of math, I think?), they found the shot to be 90% effective at preventing hospitalization, which is 12.5 percent better than what was seen in prelicensure data. There are some limitations/caveats, however.
These aren’t big numbers. A very small percentage of these hospitalized infants actually received Beyfortus. And most of the infants who did had risk factors for more severe disease. In fact, just under half of high risk babies in the study got the shot compared to only 6% of those at low risk. The results may not be fully generalizable to all infants. But if Beyfortus works really well in kids who are more likely to require admission to a hospital, it is going to work even better for lower risk kids, and there does not appear to be any concerning downsides. So the risk to benefit ratio is still rock solid in support of giving it to all babies.
That was back in December. Since then, there has been additional data that supports continued excitement about the prospects of dramatically improved RSV seasons, assuming of course that these babies get the shot. In July, the New England Journal of Medicine published a large post-licensure study that investigated the shots effectiveness at preventing hospitalization from RSV:
We conducted a prospective, multicenter, matched case–control study to analyze the effectiveness of nirsevimab therapy against hospitalization for RSV-associated bronchiolitis in infants younger than 12 months of age. Case patients were infants younger than 12 months of age who were hospitalized for RSV-associated bronchiolitis between October 15 and December 10, 2023. Control patients were infants with clinical visits to the same hospitals for conditions unrelated to RSV infection. Case patients were matched to control patients in a 2:1 ratio on the basis of age, date of hospital visit, and study center. We calculated the effectiveness of nirsevimab therapy against hospitalization for RSV-associated bronchiolitis (primary outcome) by means of a multivariate conditional logistic-regression model with adjustment for confounders. Several sensitivity analyses were performed.
The study found a reduction in the risk of hospitalization of 83%. There was also a 70% reduction in the risk of RSV disease severe enough to require admission to a critical care unit and 67% protection against the need for “ventilatory support”. These results, along with all the previous positive findings, strongly support recommendations for providing this medication to all infants.
Final final thoughts?
On a personal note, this will be my final regular contribution to Science-Based Medicine. I submitted my first post just under 12 years ago, after having been an avid reader since the debut in 2008, and a couple months after meeting David, Kimball, Steve, and Harriet at CSICon 2012 in Nashville. It was Kimball who invited me to send something in. We actually ended up working in the same hospital a year later after I moved from Baton Rouge to Boston.
12 years and over 250 posts later, I couldn’t be happier having been a part of this team. I got to meet and work with some amazing people. It gave me some recognition with journalists and even got me a brief and unsatisfying appearance on Inside Edition. I had the opportunity to speak at NECSS 3 times, and sit on several SBM panels. One of many memorable highlights for me was the time I led a panel discussion with David, Steve, and Paul Offit in 2019 right after having had a lovely green room chat with with Carl Zimmer and his wife about vaccine hesitancy.
I truly appreciate all of the experiences I’ve had related to SBM. I appreciate all the helpful, and sometimes not so helpful, feedback in the comment section. I definitely appreciate that David never told me enough already with the science-based satire posts. I obviously will never be able to quit my day job to work for The Onion.
I will probably contribute here from time to time in the future. Maybe this will just be a break for me to work on a book, perhaps a thorough take down of baby chiropractic or a collection of old Knudsen’s News posts. Here is the new Knudsen’s News site, by the way. Who knows what the future holds?
One last shameless plug. My wife, Emma Jones, is a hospice and palliative care doctor who recently published her first book. It’s about her experience with burnout as a healthcare professional and how she learned to manage it. Please consider sharing it with anyone who your feel might benefit.