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.