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I'm putting this post together on Father's Day, and tomorrow is Juneteenth, a holiday increasingly recognized in the US. Today two of my 3 sons are farther away than usual, one in Berlin, Germany, at the Special Olympics World Games and another working in healthcare in Mekele, Ethiopia. The third member of the triumvirate remains in the eastern US time zone.

Can anyone guess which state was the first to make Juneteenth a permanent state holiday?

Influenza Rising in Southern Hemisphere

The most recent World Health Organization update on influenza, published on June 12 with data current as of May 14, not surprisingly shows an uptick in flu activity in sections of the southern hemisphere. The influenza AH1N1 2009 pandemic strain and B Victoria lineages predominate, meaning we are likely in good shape from a vaccine standpoint for next winter in the US.

RSV and covid haven't increased to the same extent as flu in the south, for the most part.

Polio Vaccine for Travelers

'Tis the season for world travel, but I'm thinking many folks aren't aware of newer polio risks around the world. Spurred by the pandemic and various war zones, polio vaccination has waned. Also, as I've noted in the past we're seeing vaccine-derived polio disease via transmission from recipients of the oral live polio vaccine. The CDC continues to update polio vaccine recommendations for travelers. Twenty-nine countries around the world have circulating poliovirus, but in addition to the "usual suspects" the list now includes both Canada and the United Kingdom.

Certainly the risk can vary in settings within these countries, but primary care providers should remember to discuss vacation plans with families, not just out of interest but to make sure they are informed of any risks and where to find resources. Make sure all children are up to date on immunizations, including polio, and some adults may wish to receive a one-time killed polio vaccine booster if traveling to a high risk country.

'Demic Doldrums

Here in the US we continue with our low levels of SARS-CoV-2 circulation in most jurisdictions; now we rely primarily on ED visits and hospitalization rates for any early warning given our lack of other good community monitoring tools. The FDA VRBPAC group met on June 15 to advise on composition of the next covid vaccine, and I was able to attend most of the meeting including the important parts of the discussion sessions. All 3 US vaccine manufacturers (Moderna, Pfizer, and Novavax) presented data.

As most providers know, the XBB sublineages (XBB represents a recombination of omicron strains) now predominate; the ancestral strain has virtually disappeared from circulation in humans, as have all subsequent strains except for the omicron lineage. Without going into perhaps agonizing detail, most authorities agree that covid vaccines for the near future should focus on the XBB sublineage. The vaccine manufacturers have a fair amount of preliminary data on immunogenicity of XBB-containing vaccines. Results suggest good safety signals and good neutralizing antibody activity against currently circulating XBB strains. Less data are available for memory B- and T-cell responses to these vaccines, and nothing substantial so far on XBB vaccination of children. Work continues, and we should see more about pediatric XBB vaccination in the next month or 2.

A very important part of the presentation has to do with cross-reactivity of antibody among the various XBB strains that were tested. Because of this, a monovalent vaccine with any XBB strain is likely to be effective against these closely related sublineages. Since among other reasons all 3 companies had the most experience with the XBB.1.5 vaccine and can readily ramp up vaccine production for this product, the VRBPAC members unanimously voted to go this route and the FDA officially signed off on this recommendation. Next up is a discussion at the ACIP meeting on June 23, but don't expect any vote or final recommendations at this session. That should come a bit later. In particular, we will need guidance on pediatric use, combined use with other vaccines such as for influenza and RSV, and whether to recommend for all or just for certain high-risk populations.

Last week I perhaps dissed the CDC's use of color in their depiction of variants, but now I need to acknowledge I was wrong. The most recent MMWR had some nice graphics. The graph below not only shows the colorful distribution of variants but also the relatively low numbers of cases recently (with the caveat that testing in general is less now than in 2022).

As can be seen, we have been in an omicron world for some time, with XBB now in charge.

Quickly, a few other covid notables from last week:

Juneteenth

Perhaps not what you would have guessed, but my home state of Texas was the first to make Juneteenth a permanent state holiday, in 1980, which was decades before most of the rest of the country. I left Texas in 1984 and parts of it now are unrecognizable to me, but it's easy to understand why that state was out in front on Juneteenth. The original event was June 19, 1865, in Galveston, TX, when Union troops arrived and finally enacted the January 1, 1863, Emancipation Proclamation and freed slaves in Texas. In my childhood, unless you kept yourself under a rock, if you lived in Texas you knew about Juneteenth.

Happy Father's Day to all fathers out there, and to everyone please use Juneteenth to reflect on its many lessons that continue to challenge us to do better.

Frontline pediatric healthcare providers probably wouldn't think things are calm given our current onslaught of RSV and influenza cases crowding physician practices, emergency rooms, and hospitals. However, we are in a bit of calm of sorts for covid. Covid cases actually are decreasing in the UK and the US. Lacking a reliable crystal ball, we'll all need to wait to see whether the next few months will bring a significant rise in covid cases. In the meantime, let's explore a couple areas of interest and confusion.

How Well Do the Bivalent Boosters Work?

More time is needed for the definitive answer on this. The discussion has been going on for months, but this past week we saw posting of 2 preprint articles suggesting, based on immunologic testing, that they may not be much better than the original vaccine used as a booster, at least in terms of preventing illness after infection from some of the newer variants. This is actually what was suspected all along. The bivalent vaccine to stimulate immune response to the spike protein from BA.4/BA.5 was hoped to be a bit more effective to prevent severe disease caused by future virus variants. Carolyn Johnson's explanation of the issue in the Washington Post was excellent, please check it out. It is important to recognize that these 2 studies were based on very few individuals and have not undergone peer review. However, the reports are from generally reliable teams at Columbia University/University of Michigan and Beth Israel Deaconess Medical Center. I don't expect big changes in the results once the peer review is completed.

I want to expand on one concept mentioned as an explanation for the findings in both articles, that of immunologic imprinting. This phenomenon also has been referred to as original antigenic sin.

This imprinting is very different from filial imprinting, like baby ducks following the first thing they see after birth. Original antigenic sin refers to the 60+ year old observation that our immune systems like to use the memory of our response to an infection with an antigen (virus in most cases) when infected at some future time with a variant of that antigen. It could potentially interfere with a more robust immune response to that new variant. Of course, covid didn't exist when it was first described; the main subject was influenza at that time. Scientists developing new vaccines have been well aware of this phenomenon for decades. Covid vaccine development has incorporated this concept.

A key point: although it's possible the bivalent vaccines aren't that much better than the original vaccines when used as boosters, any booster is far better than no booster. Please encourage everyone eligible to be fully vaccinated and boosted for COVID-19.

[I realize I haven't mentioned this in a while, but some may wonder about my frequent use of Wikipedia in my links. For many medical issues, I find Wikipedia to be highly accurate plus a little more understandable to non-medical folks than virtually all other sources.]

Should We Worry About Polio in the US?

In general, no, but anyone lacking full vaccination against polio needs to beware. A few years ago it would have been hard for me to imagine ever saying that, but a combination of war, politics, natural disasters, and apathy make paralytic polio a real possibility now. Wild-type polio transmission was eliminated in the western hemisphere in 1991, and it still is, but failure to eradicate it elsewhere has led to vaccine-derived poliovirus causing paralytic polio across the world, including in the US. (Paralytic disease, the most severe form of polio, develops in less than 1% of infected individuals.)

For those unfamiliar with the disease (few clinicians have seen an active case of paralytic polio, unless they have worked abroad), remember that we have had 2 types of polio vaccine for many years. The live polio vaccine (aka Sabin vaccine, developed in 1961) is a weakened version of the wild virus, given by mouth, and requires viral replication in our bodies to produce immunity. It is particularly helpful in achieving immunity in populations difficult to reach by widespread immunization because the vaccine virus is excreted in stool and can be spread to others. That's mostly a good thing, but sometimes this vaccine-derived strain can undergo transformation to increased virulence and actually cause disease in others. A killed vaccine given by injection (aka Salk vaccine, developed in 1955) also is effective though slightly less so than the live vaccine. The live vaccine has not been used in the US since 2000; all polio immunizations in the US, and in most other developed countries, utilize the killed vaccine.

Even though most of us in the US are immunized and therefore protected against polio, wastewater surveillance in New York City suggests that the vaccine-derived virus is circulating in at least 5 counties, putting un- or under-immunized people at risk for paralytic polio. This situation likely is occurring elsewhere in the US, but so far we lack comprehensive wastewater polio reports. Data from London suggest the problem is widespread.

The pandemic and ongoing anti-vaccine rhetoric has disrupted vaccination programs in the US. Let's hope we don't see more cases of paralytic polio in the US.

Interested readers can learn more about the history of polio from the Global Polio Eradication Initiative.