Some Good, But Preliminary Real World Data on Those Baby RSV Shots – GWC Mag

When I last wrote about Beyfortus, the new RSV antibody shot recommended for most infants and even some toddlers, it was December and the manufacturer had dropped the ball. Demand was “higher than expected”, because apparently nobody spoke to any pediatricians or parents in Boston, and I was having to discharge most of my newborn patients home unprotected* after having had a steady supply for several weeks. Our experience of high demand was, not unexpectedly, an outlier:

However, uptake varied across the country. Dr. Alexy Arauz Boudreau, associate chief for pediatrics at Massachusetts General Hospital, told ABC News between 80% and 90% of families in her patient population had their children immunized against RSV.

Comparatively, Bartlett said the immunization was offered to parents of newborns before hospital discharge and more than half of families declined, which she called “discouraging.”‘

ABC News January 26, 2024

Dr. Bartlett is a professor of pediatric infectious disease at Comer Children’s Hospital in Chicago.

I dug into the available data on Beyfortus uptake across the country and found wide disparities, and also that an overall disappointingly low number of qualifying children received the proven safe and efficacious medication. What was to blame? In addition to the early supply problems, which didn’t truly ease up until January, the degree of hesitancy and even how the shot was promoted by state medical officials almost certainly differed significantly from region to region. Florida, we are all looking in your direction right now.

In fact, according to the CDC’s Immunization Information System data, which collects data on vaccines given from most states, Florida appears to have put the fewest percentage of Beyfortus shots into the arms of qualifying babies. This particular dataset is limited in that it only includes children who were eligible (birth to 7 months if first RSV season, 8 to 19 months with risk factors for severe disease in 2nd season) prior to October 1st of last year, and who would not age out during the current season. So when it says that Beyfortus uptake through the end of January was 0.7% in Florida, with only 1.6% of the higher risk babies less than 8 months of age, it doesn’t include a lot of eligible children who were born during the entirety of the RSV season. I doubt that things changed dramatically in babies born later in the season, because Florida.

IIS data generally underestimates true immunization rates, largely because of delays/problems with reporting. Perhaps their courier was eaten by an alligator. Still, it is probably safe to assume that this says something fundamentally true about Florida, Alabama, Texas, and other states with single digit percentages of that initial cohort of eligible kids getting the shot.

Alaska came in on top, reporting that 21.6% of that cohort of younger infants at the beginning of the season got the recommended dose of Beyfortus through the end of January. No state did particularly well in this dataset, however, though Massachusetts was not included. Maybe all of our courier were eaten by…a Boston Terrier? But I’m confident that our numbers were much better.

According to a different batch of CDC data compiled through the end of February, it does indeed look like uptake of Beyfortus increased dramatically once supplies stabilized. In October of last year, only about 13% of infants less than 8 months of age got the shot. This increased to 43% in February. This data comes from the National Immunization Surveys, which involves randomly calling the cell phones of pregnant women and only included about 600 respondents per month. It is interesting, and likely reflects a true trend in some regions, but take it with a grain of salt because NIS data tends to overestimate compared to the IIS.

The bottom line is that less than half of infants at the highest risk of severe RSV disease will have received Beyfortus this season. Many of those that didn’t were born to mothers who got the RSV vaccine during pregnancy, but many, and probably most in some states, weren’t so lucky. Hopefully next year will be better, and I think it will if only because there will be a more stable supply. But there may be another reason.

As the end of the official RSV season is nearing, there is now some preliminary post-rollout data showing that Beyfortus may actually work even better than predicted. Just last week, the CDC released a report on the effectiveness of Beyfortus in preventing hospitalization with RSV.

For the report, CDC researchers looked at eligible infants who were less than 8 months old on October 1st of last year, or born after that date, had a known Beyfortus status (got it or not), and were admitted to a hospital for an acute respiratory illness through February 29th. They excluded babies whose mothers had received the RSV vaccine or who had received the other RSV antibody, which is called Synagis and is only used for a select population of premature infants, has been around for decades, isn’t great for many reasons, and is going to be replaced by Beyfortus. They also had to have had RSV testing performed.

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.

Prelicensure data went out to 150 days after dosing. In this batch of babies, time since dosing ranged from 7 to 127 days with a mean of 45 days. The low numbers of RSV cases didn’t allow researchers to tease out effectiveness over time, but it is likely that it does wane somewhat. Also this study only looked at hospitalization. It seems obvious that if the shot reduces hospitalizations, especially if it does so in the highest risk babies, then it would also effectively reduce the risk of outpatient and emergency department visits. But more data is needed and certainly will be forthcoming.

Beyfortus has pediatric healthcare professionals and families excited about the possibility of a major reduction in suffering from an extremely common viral pathogen. We are hoping that the ultimate outcome will be similar to what happened with rotavirus after a safe and effective vaccine was introduced in 2006. Rotavirus used to make 2.7 million infants and toddlers ill with vomiting and diarrhea each year in the United Stats, putting 50,000 to 70,000 kids in the hospital for severe dehydration and killing 20-50 of them along the way. The vaccine has reduced hospitalizations by 80% and I haven’t seen a severe case in 15 years.

But no childhood immunization works that sits in a refridgerator.

*At the time, only handful of my patient’s mothers had been able to get the RSV vaccine approved for pregnant women as a method of reducing serious RSV disease in young infants. The benefit is believed to be similar, though my suspicion is that it will not end up being as effective as Beyfortus. That issue also improved over the next several weeks, though a small but significant percentage of mothers declined the vaccine in favor of the postnatal dose of Beyfortus.