In the Spring, a Young Man’s Fancy Turns to Thoughts of … Ticks?

OK, I know I'm not a young man, but let me dream a little bit. March 20 is the first day of spring, actually starting at 5:24 PM EDT in the Northern Hemisphere. I was reminded of spring recently when my wife, who spends approximately 86% of her waking hours outdoors, noticed a tick crawling on her arm. In my warped world view I immediately think of tick-borne diseases.

But first, a couple updates.

Paxlovid Poised for Full Approval (for Adults)

FDA's Center for Drug Evaluation and Research Advisory Committee met on March 16 to consider newer data on Paxlovid, the oral combination of nirmatrelvir and ritonavir authorized for SARS-CoV-2 treatment in selected situations. It was no surprise to anyone that data were favorable and likely will lead to full approval for individuals meeting criteria who are 18 years of age or older, but don't expect any new changes for the pediatric population yet. You can view all the documents at the meeting document site. I was more interested in the data on rebound, and the meeting documents (I didn't tune in to the sessions) had a very balanced and nuanced assessment.

First of all, recognize that rebound really involves 2 issues: viral rebound, meaning the amount of virus present drops, then bounces back up; and symptom rebound, meaning symptoms improve and then return. Also, true rebound implies a period of improvement, followed by an increase in virus or symptoms. If there is no improvement, you can't really detect rebound per se.

That all aside, the bottom line (see page 70 of the pdf, slide 59) from all the analysis from FDA was that "...rebound ... is not clearly associated with PAXLOVID treatment, is not associated with severe disease outcomes, and likely reflects natural COVID-19 disease progression and/or technical variability in virology assessments." In other words, although data continue to be collected, for now we can forget about rebound influencing treatment decisions.

The analyses involved 3 different trials including the original trial for authorization plus some trials that were primarily pre- or during omicron circulation. Most importantly, all have shown good efficacy against disease progression and excellent safety profiles, but the numbers from the omicron era (EPIC-SR 2022) are still too small to provide any separate conclusions for current times. That's been a problem with covid all along - by the time we have solid data, we've moved on to a new variant.

For the rebound consideration, here is a summary slide for combined outcomes that gives you an idea of numbers of subjects studied. Note that in the original EPIC-HR trial there was no difference in symptomatic viral RNA rebound.

The meeting site has a ton of other interesting data. I've just highlighted some key aspects.

Also on a slightly related matter, FDA has authorized the Pfizer bivalent vaccine to be used as a booster dose for children ages 6 months through 4 years, joining authorization for the Moderna bivalent vaccine booster for similar ages. It's important to remember that the primary vaccine series for Pfizer is 3 doses and for Moderna is 2 doses, both using the monovalent vaccine. Now we need to wait for CDC/ACIP to weigh in with recommendations.

What we are witnessing is the start of incremental assessments that I hope will lead to use of whatever bi- or multi-valent vaccine might be proposed for next fall, ideally for both primary series and booster doses. If analyses support this change we'll live in a simpler world of covid vaccines for children.

Babesiosis

When was the last time you worried about babesiosis? It's not on the list of commonly encountered infections, but newer CDC data just published should at least put it on our radar. The report covers the years 2011-2019 and shows that the infection is still relatively rare. However, the low numbers might be misleading because the infection is not nationally reportable and often is asymptomatic or self-limited in healthy individuals so can go undetected.

In the 10 states where babesiosis was reportable over this time period (Connecticut, Maine, Massachusetts, Minnesota, New Hampshire, New Jersey, New York, Rhode Island, Vermont, and Wisconsin), numbers increased significantly in 8 (Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York, Rhode Island, and Vermont). Of further interest is that Maine, New Hampshire, and Vermont previously have not been considered to have endemic babesiosis. Clearly we need more states to make babesiosis case reporting mandatory, but I say this knowing that many states are decreasing their public health vigilance generally.

Here's the geographic picture, based on state of residence:

If you aren't too clear about the management of babesiosis, the CDC has excellent resources for healthcare providers and for the lay public. Remember that it is a parasite that infects red blood cells, similar to malaria. Signs and symptoms often are nonspecific (febrile flu-like illness) and thus very difficult to diagnose unless hemolytic anemia develops. Individuals with asplenia, immunodeficiency, and advanced age are at highest risk of severe outcomes.

Peripheral blood smear of Babesia infection:

Another problem with babesiosis management is that some individuals carry this diagnosis falsely, on the basis of unapproved laboratory testing and misguided (or worse) clinicians. I've spent much more of my time disproving Babesia diagnoses than in actually diagnosing and treating true cases. Most of the children and young adults in my practice who were misdiagnosed had prolonged fatigue or other symptoms that weren't suggestive of babesiosis. Consultation with a reputable pediatric infectious diseases specialist is wise if a babesiosis diagnosis is entertained. Avoid so-called practitioners ordering large batteries of non-FDA approved tests for patients with vague symptoms.

Alfred Lord Tennyson

Tennyson is perhaps best-known for his poem, Charge of the Light Brigade, describing the fateful Battle of Balaclava during the Crimean War (1854, not the current Ukraine/Russia war). Thinking about spring allowed me the pleasure of rereading another of his poems, Locksley Hall, first published in 1842. It was even more pleasurable for me because I opened my copy of the slightly more modern (1892) complete and unabridged The Works of Alfred Lord Tennyson printed by Macmillan Standard Library. It's a long poem, but the pertinent passages for spring are:

"In the Spring a fuller crimson comes upon the robin's breast;
In the Spring the wanton lapwing gets himself another crest;

In the Spring a livelier iris changes on the burnish'd dove;
In the Spring a young man's fancy lightly turns to thoughts of love."