We are officially in summer as of last week, and it certainly feels like it. Barring a mid-day thunderstorm, I'm going to sweat my way through mowing the lawn after I finish this post.
An Almost Marathon ACIP Meeting
The Advisory Committee on Immunization Practices met June 21 through 23 and covered a lot of ground. I was neither able (nor highly motivated, given the number of hours involved) to tune in to everything, but I did review all the slides and attend most of the discussions dealing with pediatric issues. I came up with some take-home messages. Note that the slides are all posted at the web link, and the meeting recording should be available in a few days.
General Thoughts
For influenza next season, egg allergy is further clarified: "Egg allergy in and of itself necessitates no additional safety measures for influenza vaccination beyond those recommended for any recipient of any vaccine, regardless of severity of previous reaction to egg." Allergy to the vaccine itself is an important consideration, but mere egg allergy is not. This statement conforms to existing scientific data and will make things much easier for healthcare providers and vaccine recipients.
A general overview of vaccine safety was presented on Friday, and it might be worthwhile for all healthcare providers to review at least the first portion so that they can better explain this extensive safety network to vaccine recipients and providers. Also, the latter portion discussed data on a possible link between vaccine aluminum cumulative exposure and subsequent asthma diagnoses. At this point, the association using US data is very weak but is being studied further. A study from Denmark using much better data (the benefits of a national health system) showed absolutely no association, but of course that's a different population from the US and also different vaccine schedule. Providers who are questioned specifically about this could refer to those slides.
Remember my June 11 post when I was grumbling about a movement in Congress to ban use of QALY (Quality Adjusted Life Years) by CMS? If you removed QALY analysis from this meeting, the ACIP couldn't have moved forward on anything. I'm hoping this congressional movement will get ditched, but keep an eye on it.
Also in general, we are lacking information about co-administration of newer vaccines with existing vaccines. This isn't unusual, but in some instances it could be pertinent. Prominent among those is the RSV vaccine for older adults, of course not a pediatric issue, and also lacking is efficacy information in the 85 and older and frail groups. For those specific items we will have more information eventually.
Pneumococcal Vaccine
Most of this segment centered around Pfizer's 20-valent conjugate vaccine in children. Because there are already several versions of pneumococcal vaccines available, both polysaccharide and conjugate forms, the possibilities seem endless. The committee discussed various options for children who are in the midst of their vaccine series and included regimens and combinations that have not been studied. Probably we will see formal recommendations soon, but pneumococcal vaccination is clearly the most confusing set of guidance in all of vaccinology even before the 20-valent option surfaced. This is because recommendations vary with age and specific risk groups. I can't even keep it straight in my head what I'm supposed to do for myself. Fortunately, there's an app for that. CDC has a wonderful tool called PneumoRecs, available for use on a computer or for download for Apple and Android phones. It works for all ages and risk factors, you just input specifics about your patient's age, risk factors, and prior vaccine history and poof you know what to do.
Meningococcal Pentavalent Vaccine
Meningococcal vaccination guidelines are very confusing as well, but also it is by far the most expensive (based on cost-effectiveness) vaccine recommended for routine use. This is because meningococcal disease is actually pretty uncommon, so vaccination doesn't prevent much morbidity and mortality particularly for meningococcal B disease. Meningococcus group B protection is more important for certain types of immune compromise (e.g. asplenia or terminal complement component deficiency) but used commonly for the college student age group. Many years ago I accepted the fact that many colleges are requiring it for their incoming freshmen, it is now more of a legal liability protection and I guess a measure of reassurance to parents whenever a college dormitory mini-cluster occurs.
The pentavalent vaccine combines the groups A, C, W, and Y in the existing quadrivalent vaccine with group B which now exists as a separate vaccine. ACIP did not have a vote on the pentavalent vaccine, it is still a work in progress. I did find a few epidemiologic graphs very informative. The graph below shows that meningococcal disease was declining significantly before the introduction of any vaccines in the US, making it difficult to know how much vaccination contributed to any further decline.
Second, the current number of cases is very low, and the numbers of cases in the 11-15 year olds would suggest that we should revise current recommendations.
The problem is that meningococcal immunity likely wanes significantly within a couple years after vaccination. So, giving a first dose of quadrivalent (or potentially pentavalent) vaccine in that 11-12 year old group is providing protection at the time they need it the least. That first dose should come later.
Regardless of the current vaccine recommendations, it is very clear that active and passive smoking is a significant risk factor for invasive meningococcal disease. Smoking increases binding of meningococci to respiratory epithelial cells, a major initiating event for invasive infection. Smoking reduction, including vaping though no specific vaping studies are available, is the most effective preventive measure against meningococcal disease in healthy adolescents.
Also keep in mind that epidemiologic trends might be different post-covid, as we saw initially for influenza and RSV.
RSV Prevention for Infants
This was primarily a discussion of the Pfizer RSV vaccine for pregnant people, without a vote by the committee meaning more to come on this decision. A major question regarding maternal vaccination is a possible association with premature delivery in recipients. The forest plot below shows a slight increased risk of preterm births.
What is particularly tough is that another maternal RSV vaccine study with a different manufacturer was stopped because of an increase in preterm births in the vaccine recipients compared to placebo. It's still not clear what the potential biologic mechanism would be for such an association, but for now this is a significant concern. Thankfully we are likely to have the long-acting monoclonal antibody, nirsivemab, available for the upcoming RSV season.
What I'm not including in this post, because I'm not smart enough to summarize effectively for a nonstatisticians and similar geeks, is the very elegant and thorough discussion of costs of various scenarios for RSV prevention in young infants. These considerations included using maternal vaccine and infant monoclonal antibody treatment, both separately and in combination. The combination is likely not going to be clinically- or cost-effective. Separate use (e.g. nirsevimab for mothers who did not receive vaccine, or infants born prematurely prior to maternal antibody transfer across the placenta) is difficult because providers may have difficulty accessing accurate maternal vaccine records. It's a bit of a messy consideration. Still, I wanted to at least introduce one new concept of tornado diagrams. I had great trouble even finding a user-friendly explanation for the link, but keep in mind that it is a method to determine the major factors driving cost-effectiveness. As stated in the link, big bars are the big drivers, small bars aren't. (The name comes from the shape of the graph - imagination required, nothing to with the weather.) Here is a tornado graph for nirsevimab.
It sort of looks like a tornado shape? The biggest drivers, which translate to a sensitivity analysis of how accurate the cost-effectiveness analysis is, include cost of nirsevimab, costs of hospitalizations, and our old friend QALYs lost. As you can see from the Incremental Cost-Effectiveness Ratio (ICER, the ratio of differences in cost between 2 options divided by the difference in effects such as QALYs) scale at the top, these are big bucks. I'm certainly no expert in ICERs and tornado diagrams, but this type of analysis is critical in choosing among various healthcare interventions at the population level.
I'll continue to keep my eyes peeled for better explanations of ICERs and tornado diagrams.
'Demic Doldrums
Hooray, we are still in a covid lull, including most places around the world including southern hemisphere. You can look at the good news in detail on the WHO website.
ACIP did discuss covid vaccines, briefly, but no significant new data to report. We are likely on target for monovalent XBB.1.5 vaccines available from all 3 US manufacturers by September. Also, look for some dosing simplification for the 2-4 year olds.
Off to the mower, after I drench myself in DEET.