omicron variant – Page 6 – Pediatric Infection Connection

Calm Before the Storm, or Just Calm?

Bud WiedermannMay 28, 2023May 28, 2023Leave a comment

We seem to have settled back into the good old days of infectious diseases and outbreaks, always something going on but at least nothing on the level of the past 3 years. Certainly we'll see an upswing in covid sometime in the coming months, but in the meantime I will try to return this blog to something approaching normality.

Short Antibiotic Course for Community-Acquired Pneumonia in Children

A group of Chinese investigators, working with McMaster University experts in evidence-based medicine, reported a meta-analysis looking at treatment duration in randomized controlled trials of antibiotics for pediatric CAP. Let me say from the start that this study is an excellent example of how to perform a high quality meta-analysis. I came to that conclusion before I realized that the McMaster group was involved, in particular Gordon Guyatt who is one of the world's leading researchers in EBM methodology.

The group defined short-term treatment as 5 days or less and found that shorter duration did not seem to alter outcomes compared to longer treatment. Here is one of the Forest plots looking at treatment failure of 3 or 5 days of antibiotics versus 5, 7, or 10 days:

This is one of many forest plots (also known as blobbograms, don't you love that!) including multiple subgroups that together provide reassurance for short-course therapy for CAP. The authors spent considerable time looking or sources of potential bias, somewhat difficult because each of the included studies had differing definitions and methodologies.

The children in these trials had relatively mild CAP, so the results shouldn't apply to those with more severe CAP. Also, It is likely that a large proportion of study subjects had viral infections. As the authors mention, "... it is usually extremely difficult to distinguish between viral and bacterial CAP." Still, the takeaway message should be to consider short (or no) antibiotic therapy for mild pediatric CAP.

Human Papillomavirus Transmission from Pregnant People to Their Neonates

Investigators from multiple Canadian institutions reported a prospective cohort of 1050 pregnant persons and their newborns with regard to HPV infection rates in the mothers, along with HPV detection in placentas and rates of positivity in their infants followed for a 6-month period. Note that the study recruited mothers early in pregnancy in the time period of 2010-2016. The bottom line was that 40%(!) of mothers had detectable vaginal HPV, but only 92/860 (10%) of tested placentas were positive. Detection of HPV from any site (conjunctival, oral, pharyngeal, genital) in newborns at birth or at 3 months of age was positive in about 7%, but no infant was positive at 6 months of age at any site.

This is a nice study and is somewhat reassuring that HPV transmission from mothers to infants in utero or perinatally is not a large problem. Of course, having seen innumerable infants with tracheal HPV, I can vouch that even an uncommon event like perinatal HPV transmission can result in severe consequences.

'Demic Doldrums

Please excuse my stretch to find an alliteration for this topic. Until we see the next covid wave, I liken this time to the doldrums. If you, like Jack Aubrey*, command a ship in the early 19th-century British Navy, the doldrums are to be feared; an absence of wind means your ship is stalled. It's not easy to row a 3-masted vessel in the ocean. However, a pandemic doldrum is a good thing. I'll include some 'demic doldrum postings as a semi-regular feature in upcoming blogs.

This past week had a few covid highlights worthy of mention. First, investigators at the University of Warsaw, Poland, reported 3- and 6-month echocardiographic evaluations in 172 consecutively diagnosed children with Multisystem Inflammatory Syndrome in Children. All of the subjects were asymptomatic from the time of their MIS-C hospital discharges. Results were quite good, even in those with initially severe cardiac involvement.

Along similar lines, we have some new data on safety of the Pfizer covid vaccine with numbers on myocarditis/pericarditis rates. It's a US commercial claims database analysis from the FDA and other organizations (but no contribution from Pfizer, so less chance of bias) and covers 3 million children 5-17 years of age. It looked at rates after both the primary series and after a third vaccine dose. Out of 20 different adverse events monitored, only myocarditis/pericarditis showed a safety signal but just in children in the 12-15 and 16-17 year age groups. The average rate for this complication was 39.4 events per million vaccine doses and tended to occur about a week after the primary series. The investigators were able to perform medical record reviews on only a subset of the events to verify diagnoses. This study is an example of the type of post-marketing data we need to continue to follow vaccine recipients for adverse events and is encouraging that nothing new is turning up so far.

We also have evidence of progress on the long covid front, more appropriately termed PostAcute Sequelae of COVID (PASC). We now have a better case definition. That may not sound like a big deal, but for something this complicated a good case definition is essential to figuring out diagnostic and management trial design and best strategies. A group from multiple institutions in the US developed a scoring system based on study of almost 10,000 adults. Signs and symptoms found to be significant enough to include in the scoring include postexertional malaise, fatigue, brain fog, dizziness, gastrointestinal symptoms, palpitations, changes in sexual desire or capacity, loss of or change in smell or taste, thirst, chronic cough, chest pain, and abnormal movements.

Meanwhile, it's time to pay attention to the southern hemisphere, just as we do for influenza, since it could be a harbinger for what we'll see in a few months. We don't have the same level of monitoring as early in the pandemic, but I will keep my eye on Australia, where cases are rising in almost all states though still at a low level.

Lastly on the covid front, variant studies such as those in the UK continue to show we are living in an XBB variant world. I'm also keeping my eye on a new one, EM.1.

*Jack Aubrey is the fictional British naval officer appearing in 20 (+1 uncompleted) novels by Patrick O'Brian. I've read all the books and was pleased to see the first in the series recommended for summer reading by the Washington Post's (and fellow Silver Spring resident) Michael Dirda. The books take a little work, a lot of unfamiliar terminology and details to get through, so not quite the easy beach read. You may be more familiar with the movie Master and Commander which was actually a combination of events from 3 of his books.

Whatever you're up to this summer, try to make room for curling up with a few good reads.

Default Dedebt?

Bud WiedermannMay 21, 2023May 21, 2023Leave a comment

Living in the DC area, it's impossible to ignore the news on the looming debt ceiling deadline. Thankfully, we don't have a lot of infectious diseases causing immediate worry.

It's RSV Week

No, we haven't had any bizarre spring outbreak of RSV disease, just a spring outbreak of RSV news.

I wasn't able to view the FDA VRBPAC meeting about the Pfizer RSV vaccine for pregnant women, but I've gone over the documents, slides, and news reports. From a superficial view, the committee members voted unanimously that the vaccine, administered to pregnant people at 24-36 weeks gestation, was efficacious in preventing medically-attended lower respiratory tract infection (MA-LRTI) in their newborns from birth through 6 months of age. They also voted that the vaccine was safe, although 4 of the 14 panel members voted "No" for the safety issue.

Looking at the efficacy numbers, the vaccine efficacy was 57.1% (95% CI 14.7-79.8%) for RSV+ MA-LRTI and 81.8% (40.6-96.3%) for severe (defined as tachypnea, oxygen desaturation, need for high flow cannula or ventilatory support, ICU admission, or unresponsiveness) RSV+ MA-LRTI. The main trial involved about 7000 mothers, randomized equally to vaccine or placebo. As you can see, the confidence intervals are quite large, indicating the relatively low numbers of the outcomes of interest. Efficacy for severe disease dropped to 69.4% at 6 months of age, again with a wide confidence interval. The numbers are pretty good for a respiratory viral vaccine. Here's a screenshot of one of the FDA presentation slides for severe disease:

For safety evaluation, both mothers and infants were studied. The main concern that arose had to do with a higher rate of premature delivery in the vaccine group. Here's the safety summary from the FDA presentation:

You can see that the premature births/deliveries percentages are close to one another, and the differences did not reach statistical significance. Still, it is notable if in fact there is some causal association - remember, it would be a vaccine potentially given to all pregnant people. Also, it's a bit more concerning because over a year ago GlaxoSmithKline paused their trials of a maternal RSV vaccine over safety concerns. The safety concern with the Pfizer vaccine would likely require tens of thousands of participants in new clinical trials to have enough power to see if the relationship holds; rather, this would be something to focus on with post-marketing surveillance if the vaccine is approved.

At the time I write this, FDA has not yet issued an approval statement for the vaccine. Of course, we have plenty of time since the next RSV season is likely months away. Also, we must remember there is another potential new alternative for RSV severity mitigation in young infants, the long-acting antibody preparation nirsevimab. The CDC's ACIP will discuss maternal/pediatric RSV prevention at their meeting on June 22. It may be that nirsevimab is a better choice than vaccine at this point. I'll be very interested to follow that June ACIP meeting.

But Wait, More RSV

A couple new studies appeared last week. One longitudinal cohort study in Tennessee demonstrated an association between lack of RSV infection in the first year of life and lower risk of asthma developing within a 5-year followup. This isn't the first study revealing that early RSV infection can lead to subsequent asthma diagnosis. The study involved only term infants, suggesting significant potential benefit of RSV preventive measures beyond just premature infants.

Another study from Colorado reported that lack of exposure to RSV during the bulk of the covid pandemic could be the reason we saw such a severe RSV season this past fall and winter. We'll need to see the results replicated in other locales, but the study was well done and the mechanism is biologically plausible.

Covid News

Not much has changed in the past week, but a few items of interest appeared. First, the World Health Organization has recommended the next iteration of vaccine be a monovalent product targeting the XBB lineage, abandoning any inclusion of the ancestral strain. I'll be interested to see if the US follows suit when FDA meets June 15 to discuss composition.

A recent modeling study also caught my attention. As I've said before, modeling studies have many assumptions and can end up being totally off base, but this one from multiple institutions shows that, if we had done a better job with covid booster vaccinations in fall of 2022, we would have seen a significant decrease in both hospitalizations and school absenteeism in the pediatric population last winter. Perhaps I'm cherry-picking this study because it agrees with my bias that covid vaccination benefits all age groups, but the study methodology seems sound given the limitations of any modeling study.

Lurking in the Shadows

Mpox remains a problem, particularly for men who have sex with men. The vaccine is highly effective.

Influenza H5N1 continues to lurk, causing sporadic infection primarily among those with very close contact with fowl including chickens. The US Department of Agriculture is studying a vaccine for poultry as well as use of other mitigation strategies.

CDC has some new guidance on building ventilation, maybe one of the lessons learned from the pandemic that would be useful to implement now in your office and/or home, depending on need and available financing.

I'll keep my eye on all these shadows, but in the meantime I'm turning my attention to a more practical matter of my carport's battle with carpenter bees. Listen to the soundtrack in the link, it sounds like it came from a bad horror film.

The Gospel of Meta-Analysis

Bud WiedermannApril 30, 2023April 30, 2023Leave a comment

Well, definitely no gospel with this study design type, though sometimes it seems as if some medical researchers place MA on a very high pedestal. In the days when I was teaching a graduate school course in evidence-based medicine, I asked learners to approach MA as the most dangerous form of medical study, because so few people were aware of the nuances of study design and how that could impact interpretation and translation into clinical practice.

This past week I saw 2 new MA studies published that offer an opportunity to look into this more deeply.

Time to Buy Ocean Spray Stock?

Definitely not, but the granddaddy/momma of all MA and EBM, the Cochrane Library, has a significant update to its MA of use of cranberry juice and related products to prevent urinary tract infections. Cochrane is the ultimate in high-quality MA with a very standardized process to conduct such reviews and a rigorous editorial process. Access to full Cochrane reviews requires a subscription, but the summaries and often helpful "Plain language summaries" are open to all.

However, these gold standard MAs don't always translate into immediately useful clinical practice changes. I have found them to be more helpful in pointing the way for future studies to answer lingering questions.

The current cranberry/UTI review was published last month and updates the last review published in 2012. The new update now has twice the number of studies (50) as in 2012, so gives a better estimate of effects. The entire review runs to 150 pages, just to give you an idea of the level of detail.

Below I have taken the section of the results that shows the summary analysis for studies in children; that dark diamond shows a significantly lower relative risk for children given a cranberry product as opposed to placebo or control in preventing symptomatic UTI. (With apologies for the column alignment in the table, it defeated my limited web design skills.)

As most pediatric healthcare providers know, authorities recommend limiting the use of antibiotics as prophylaxis for recurrent UTI in children, with the main use drawback being development of antibiotic resistance. Should we now recommend cranberry products for children at risk for recurrent UTI?

To answer this, we need to look closely at the methodology of the Cochrane MA, in particular the characteristics of the studies chosen for the review. This requires a close look at the dreaded Methods section of the study. Of the studies included above, Afshar, Salo, and Wan compared cranberry juice to placebo; Ferrara was a cranberry/lingonberry syrup combination compared to Lactobacillus treatment; and the Dotis study looked at cranberry capsules compared to no treatment. Most of the studies looked at children with more than 1 prior UTI, but Salo enrolled children after their first UTI. Only one study enrolled more than 100 children. So, you can see from the start that we have some highly variable study characteristics.

What is more of a problem with most MAs is the fact that, in order to include only studies of high quality where data are very clearly documented, the study milieu bears little resemblance to real-life situations. In our clinical practices we don't have access to research nurses who are hovering over all the subjects to better ensure treatment compliance and data collection. This is really the difference between reporting efficacy (how an intervention behaves under ideal circumstances) versus effectiveness (how it works in real-world situations). Also, we don't know how the cranberry intervention compares to other non-antibiotic strategies such as promoting better voiding habits in children.

This is an excellent study, and the data clearly show a benefit (efficacy) for the cranberry interventions. From a practical standpoint, I don't think I would start recommending this for children who have experienced UTI, but if a parent wanted to try it I wouldn't be opposed. Just remember, any intervention to prevent recurrent UTI must be maintained long-term; it's not something to try for a month and then forget about.

Is Covid Vaccination Associated with Bell Palsy?

The short answer: probably yes, but that's not the correct question. What you, I, and our patients should want to know is how Bell palsy (BP) rates vary between the vaccinated and unvaccinated; i.e. is the risk of peripheral facial nerve paralysis likely to be more or less with vaccination versus covid disease? A new MA study attempted to shine some light on this question. Both randomized controlled trials and observations studies were eligible for inclusion, and the studies were heavy on adults with only a few adolescent studies. The methodology was generally of high quality.

The researchers reported several outcome comparisons. Looking just at the observational studies, there were fewer "events" (BP cases) in the vaccinated versus unvaccinated participants, and many fewer events comparing vaccine recipients to people experiencing SARS-CoV 2 infection. They found no difference comparing Pfizer to Oxford/AstraZeneca vaccine recipients in observational studies. So, from these comparisons, it's very clear that if you are worried about Bell palsy, you want to be vaccinated.

What's really interesting, though, is that if you look just at randomized controlled trials comparing mRNA vaccination with placebo, the reverse was seen: vaccine recipients actually had more events.

Why are we seeing such a contradiction of associations? Well, it's not really a contradiction, it's a great example of the difficulties in both using study results and explaining them to the general public. One really needs to have an understanding of overall BP rates as well as how data are collected under a variety of circumstances.

The baseline rate of BP in the general population, without covid considerations, is around 15-30 per hundred thousand people per year. The BP rate in the vaccine recipients in the RCTs in this report was 18/100,000/year, similar to previous reports. However, the rate of BP following actual infection with SARS-CoV-2 in the general population has ranged from 32.3 to 82 per 100,000, significantly higher. So, this report still says it is better to be vaccinated against this virus than to be infected with it, which is really the question we care about most. In an RCT, study subjects might have a lower covid infection rate anyway (people enrolling in a vaccine study probably lean towards more infection-cautious behaviors than in the general population) and tracking is limited to a specified time following study entry. These are nuances between RCTs and observational studies that can make it appear that conclusions contradict one another.

All the data from this MA were from the published studies themselves; some MA are able to use patient-level data (data on individual patients, rather than the aggregate report from the publication), but his was not the case here. So, the investigators were unable to evaluate multiple factors that might have clarified our understanding. I certainly hope investigators (and pharmaceutical companies!) will move to better data sharing in the future to allow for more thorough analyses and comparisons of studies via patient-level data.

I suspect some in the anti-vax movement could take data from this study out of context to persuade people to avoid covid vaccination. If SARS-CoV-2 goes away (not gonna happen any time soon, sadly), then purely from a BP standpoint you could argue against receiving the vaccine, but we have many more examples of vaccination benefits. And, we have all now seen what happens with infections that "went away," only to flare again when vaccination rates fall. It is still better to be vaccinated against covid than to experience infection.

One more caveat - remember that these types of studies only show an association between events and cannot prove or refute cause and effect. However, with knowledge of the mechanisms of BP with other infections and vaccinations, most authorities would conclude that BP can be caused by covid vaccination, just at a lower rate than caused by the infection itself.

Meta-Analysis Fatigue?

You might well be experiencing this by now, but if you want a little more explanation I did attempt, early in the pandemic, to explain Cochrane reviews and to provide some tips about keeping up with and interpreting the medical literature. Always tough, but manageable.

(Try to) Keep It Simple 2

Bud WiedermannApril 23, 2023April 23, 20232 Comments

I had high hopes that the relative lull in covid disease would allow me to focus on other topics in this blog, but my wishes took a setback this past week mostly due to FDA and ACIP weighing in on simpler covid vaccine recommendations. While it is true they are simpler, as usual there is much complexity in the details.

The New Covid Vaccine Guidance

I was wondering what was taking so long for the FDA to update recommendations particularly for spring boosters for "elderly" (how I hate this word!) and immunocompromised individuals. Most of those individuals are several months past their last vaccine doses, and most studies show significant waning of protection after about 3 months. Well, it turns out they may have been waiting for the next regularly scheduled meeting of the ACIP on April 19, because they released their simplified authorization for bivalent vaccines on April 18. Both agencies recognize the need for simplicity if we are to see any improvement in the horrific vaccination rates in our country.

Still, lots of questions remain. I tuned in to the ACIP meeting, let's look at some highlights of their presentation.

To summarize a large amount of data, vaccine safety signals continue to be very encouraging. Separately, a new publication in Pediatrics showed a lower rate of vaccine-associated myocarditis in adolescents than had been reported previously, using data from the VAERs system.

No matter what angle you use to look at the data, the benefits of vaccination clearly outweigh risks even in the present day where most of the US population have some degree of immunity from prior infection, vaccination, or both. Here are the latest pediatric antibody data:

Looking and listening to the early presentations, I was most struck at the very effective safety tracking systems in place, composed of both old and new methods of safety assessment.

It's important to recognize that each of these systems involves different methodologies and looks at different aspects of safety. I was eligible for and received my second bivalent booster last Friday. (I should note, I'm considered "elderly" in the US in terms of this bivalent booster, but not in the UK where apparently age 75 is elderly and I couldn't have received a booster!) After my injection, I decided to look into v-safe again. I'm glad to say that v-safe is still operational and thus I was able to report on my symptoms, which were none. Those of you who have used v-safe in the past, as I have done for all 6 of my own covid vaccines, know that it asks about specific, common, side effects. It's great to monitor those rates, but it isn't a system that is designed to catch rare side effects of the vaccine. Other systems do that quite well, however, though still tough because we're talking about such extremely rare events that may occur at similar rates in the general/unvaccinated population.

Dr. Ruth Link-Geddes presented data on vaccine effectiveness against symptomatic infection in young children, collected through the ICATT (Increasing Community Access to Testing) system. VE is a difficult and somewhat moving target since vaccine uptake is so low in this population, it might vary with brand of vaccine and time since last vaccination, and, as usual, the variants are changing. As you can see, the data are very current.

Note that the Pfizer primary series requires 3 doses versus 2 for Moderna, and the system had too few children who received 3 Pfizer doses to break down VE further to give an estimate of how/when protection wanes.

A nice simplification for practices administering covid vaccines is the decrease in types and appearances of vials needed:

Now for the complicated details. It was clear that not all scenarios have been addressed, especially for the pediatric population. One such messy detail is the difference in age cutoffs between Moderna and Pfizer vaccines, with a transition at the 6th birthday for Moderna and the 5th birthday for Pfizer. As Dr. Sarah Long brought up in the ACIP meeting, there's not much difference immunologically in the 4 - 6 year old age group, but currently we are stuck with confusing guidance simply because the 2 companies chose different age breakdowns for their clinical trials. The FDA needs to get past this.

Also, it was very clear that ACIP (and FDA) have said nothing about spring bivalent boosters for severely immunocompromised young children such as transplant recipients. As it stands now, they have no option to receive another vaccine until perhaps fall 2023, yet they are among the most vulnerable populations. We don't have results from studies in this population, but that's not a compelling reason to hold off making a recommendation for the interim period. Perhaps other organizations (American Academy of Pediatrics, et al) need to press FDA and ACIP on this matter.

Another gap in the new guidance is what to do about healthcare providers. It seems like eons ago, but HCP were given priority in the initial vaccine rollout as a means to provide some protection to vulnerable populations and also try to preserve HCP availability to provide care during peak pandemic disease periods. It is perhaps not as crucial now, but given that some are calling for removal of universal masking in healthcare settings, how about considering a system of choosing either masking or another booster for those HCP? Masking in general isn't a big deal for most, but it is another expense and we do need to be cognizant that it does interfere with communication, especially for those whom English isn't their primary language or for those with hearing impairment and other disabilities.

CDC has updated their web page with these changes, though it's a load of words and tables that make it very tough to get the picture quickly. I"m hoping they come up with a more graphical decision aid soon. Also, a COCA call webinar to explain all this to HCP is planned for May 11, though the listing is not yet posted on their website.

Statewide Variation in Covid Policies

An article from The Lancet caught my eye. It is based on database analysis and funded by organizations mostly supporting vaccination and other public health preventive measures so must be taken with a grain of salt. However, it did demonstrate that "State governments' uses of protective mandates were associated with lower infection rates, as were mask use, lower mobility, and higher vaccination rate, while vaccination rates were associated with lower death rates." Gross domestic productivity and reading test scores were not associated with state policies, but lower 4th grade math test scores were associated in some settings.

A New Approach to Antibody Treatment

We have been through the whiplash of having effective monoclonal antibody treatments available at different times during the pandemic, only to see them rendered useless when a new variant takes over. Much research is ongoing to find a better way, and one might be the use of recombinant polyclonal antibody treatment as mentioned in this article from a California company. It's just an in vitro article, a long way from efficacy trials, but expect to see more about this approach.

Those Pesky Variants

Speaking of variants, the XBB sublineage has taken over in the US according to CDC data, and that XBB.1.16 strain that I mentioned had grown dramatically in India is now projected to have some advantage in both the US and the UK. It appears to be very agile with immune escape, but not much data yet on severity of disease. XBB.1.16 is the dark blue at the bottom of the vertical bars below.

The Simple Life

Once again I fell into the trap of being led from contemporary entertainment to the book on which it was based. This time it's the Richard Russo novel, Straight Man, on which the AMC series "Lucky Hank" is (somewhat loosely) based. I've only seen 2 or 3 of the TV episodes, but the book highlights Occam's Razor. I've used this reasoning aid in my clinical diagnosis thought process for years, even before I knew about its existence. It's been badly misquoted and misused, including in the Russo novel, but it does focus on simplicity. I loved that Russo's protagonist's dog is named Occam. I haven't yet finished the book but I am enjoying it - a humorous, sarcastic take on life in academia, some of which I've unhappily experienced.

A Spring in My Step

Bud WiedermannApril 16, 2023April 16, 2023Leave a comment

Both the springtime weather and a recent visit with family that included my granddaughter definitely put a spring in my step. Also useful for lawn mowing duties that have hit peak April duty.

A Worrisome Outbreak

Public health authorities recently called attention to an outbreak of hepatitis A associated with frozen organic strawberries sold on the west coast. That's not particularly unusual news. What really caught my attention was the fact that the strain of hepatitis A causing disease this month is identical to a strain that caused an outbreak in 2022. In essence, the cause of a past outbreak was identified, but whatever measures were taken to stop the outbreak didn't prevent the current one.

The FDA first warned of the current outbreak in February 2023, but an April 11 update (scroll to bottom of the page) identified the strain as being the same as last year's outbreak; the supplier is in Baja California. Multiple retailers had offered the products for sale, including big name stores such as Costco, Aldi, and Trader Joe's.

Currently only 7 infected individuals in 2 states have been identified, but this is always an underestimate since many people with hepatitis A never receive testing.

Those of you not residing on the west coast shouldn't feel entirely safe. The 2022 outbreak spread to the midwest, and the strawberry products in the current outbreak have been distributed nationwide. The products have been voluntarily recalled, but some families may have these contaminated strawberries in their freezers. Families can learn brands and lot numbers at the FDA link above.

Fauci's 10 Lessons

Dr. Fauci and his former chief of staff at NIH, Gregory K. Folkers, published a perspective article covering their top 10 lessons learned from the COVID-19 pandemic that may be useful in further pandemic planning. It's not anything particularly new or startling but nice to see gathered in one place. I was particularly struck by #1 ("Expect the unexpected.") and #10 ("Emerging infections are forever."). Given our current state of public health disarray in the US, I feel like we are sitting ducks for the next one. The tremendous culture wars surrounding personal freedoms combined with the strong resurgence of the anti-vaccination movement could greatly interfere with controlling the next epidemic or pandemic.

Infectious Period and Transmission of the Omicron Variant

The Health Security Agency in the United Kingdom published a great review of data regarding the omicron variant, covering the period from the start of the omicron wave in December 2021 through January 2023. It's a 54-page document, but fortunately you can read a nice summary of the main messages at the start.

Regarding the infectious period, most transmissions from symptomatic individuals occur during the first 5 days of symptoms. Similarly, peak viral loads occurred 2 to 5 days after symptom onset. Viral clearance mostly appeared on days 7 to 11 in the general population and slightly longer in more severely ill or immunocompromised groups (10 to 15 days).

Studies comparing viral loads and transmission rates from symptomatic versus asymptomatic people were mixed. The Agency could not make any firm conclusions from the studies comparing these 2 populations.

This review should be helpful as various groups try to decide on rational quarantine and school attendance policies for the near future.

Sitting Ducks

Although I grew up in south Texas in the 1950s and 60s and knew many hunters, I don't know a thing about duck hunting. The idiom "sitting ducks" that I used in the Fauci section above must come from a hunting analogy, but I was stymied in trying to pin down an accurate origin for the term; clearly it was in use during World War II. I did learn a bit about uropygial, or preen, glands that produce oil and help maintain duck buoyancy, can't wait to bring that up at my next group gathering.

In the meantime, get out and enjoy the springtime!

Tag: omicron variant