Welcome to the December 2023 Newsletter for

Santa Monica Primary Care.

In this issue, we will cover end-of-year tips and some of the things we see in a
GP practice around the Holidays. Winter is the season for respiratory viruses –
specifically Influenza, COVID and RSV. We will cover these as well with lots of
colorful graphs and even maps!

December: Not The Time to Schedule a Colonoscopy (or much else!)

Gastroenterologists of any subspecialty are busiest it seems during December. My best guess is that this phenomenon is due to patients hurrying to have screening colonoscopies before their insurance premiums reset in January. Interestingly, data from anesthesia practices (Piersa et al. 2021. Anesthesiology 135:804-812) show a 20% increase in daily caseloads during the month of December. In three years of data analysis (2017-2019), up to 24.5% more colonoscopies were performed per day in December than January through November


Gastroenterologists are not the only subspeciality that experiences this end of year rush and it does raise legitimate concerns about the availability of specialists for time sensitive and urgent cases – and not only at the end of the calendar year. It is part of a larger overall trend that I have observed with subspeciality wait times sometimes becoming unacceptably lengthy. Average wait times nationwide to see a Dermatologist average over 30 days, for Orthopedics over 2 weeks (55 days in San Diego!), and Cardiology 26 days (link: https://www.medicaleconomics.com/view/appointment-wait-times-drop-for-family-physicians-indi cating-shift-in-care).

One potential ‘fix’ to this phenomenon would be to have health insurance coverage run from July 1st until June 31st rather than from January 1st to December 31st. In this way, patients who have met their deductible would be scheduling procedures such as screening colonoscopies during the middle of the summer when sick visit rates are lower. The end of the calendar year is
always a busy time for medical practices as illnesses increase, hospitalizations increase and patients are left trying to fit in elective procedures.

COVID-19: Historically Low Rates Continue in Los Angeles (and Santa Monica)

While the Los Angeles Times recently raised concerns about a ‘tripledemic’ of COVID, flu and RSV (link: https://www.latimes.com/california/story/2023-12-05/covid-flu-rsv-on-the-rise-in-california-is-anot her-tripledemic-coming) objective data from Los Angeles County suggests that one part of that trio is not increasing. In fact, current COVID-19 rates are 65% lower than they were in the late summer and 80% lower than they were at the beginning of the year (Figure 1 below).

Smoothed Daily Incident Case Rate (Per 100,000 population) of SARS-CoV2: Los Angeles Country, California

One critique of these low rates is that most people are testing at home (if at all) so the numbers reported by the county really are not representative of the true case rate. However, using prevalence estimates (prevalence defined as the percentage of the population with an active COVID infection, calculated as a function of observed case rates, testing rates and positivity rates), we see a similar pattern with low current prevalence rates as well (Figure 2 below).

Estemated Prevalence Rate (per 100 individuals) of SARS-CoV2: Los Angeles Country, California

The most recent County-wide prevalence estimate for the week ending 11/28/2023 is 0.3% or, in other words, 3 discernable (not necessarily infectious) COVID cases per 1000 individuals.

Here at Santa Monica Primary Care, we are seeing far fewer cases than we did a year ago. Whereas in November 2022, we had 29 cases in the practice, this November we had only 6 (Figure 3 below). This extends a year-long trend wherein we have consistently seen, with the exception of September, fewer cases each month of 2023 as compared to 2022.

Total Cases of COVID-19 by Month: Santa Monica Primery Care

This may be a function of widespread blended immunity from vaccination and
community-acquired infection. General seasonal trends remain wherein we experience a large Winter (December/January) surge followed by a quiet Spring and then a mid to late summer smaller surge in cases. Historically we have seen an uptick in COVID cases after the Thanksgiving and December Holidays, so I think we can reasonably expect that this will again occur although it has not, as yet, become obvious.


The second virus of the aforementioned ‘tripledemic’, influenza, is increasing as would be expected for this time of year. Currently, 6.8% of viral cultures sent to clinical laboratories have been positive for influenza, and 4% of outpatient visits nationally have been for influenza or influenza-like respiratory illnesses. The Southeast and South-Central areas of the country are reporting the highest levels of activity (Figure 4 below).

Of the strains isolated, 74% were H1N1 and 26% were H3N2. For those that follow my monthly newsletter, we covered the selection process for seasonal influenza vaccine components in the October newsletter. Indeed, H1N1 as well as H3N2 subtypes are in the 2023/2024 formulation. So it is reassuring to see that the vaccine matches the predominant circulating subtypes. This bodes well for this season’s shot to be effective against infection entirely and more certainly in the reduction of severe disease.

RSV: Vaccination and National Trends of the Infection

Interestingly, most of the vaccination questions I have had this season have been about the RSV vaccine. To recap, there are two RSV vaccines approved for use in the United States for those 60 and older: RSVPreF3 (GSK / Arexvy) and RSVpreF (Pfizer / Abrysvo). In the UK only Arexvy has been approved for use for those over the age of 65 as the data presented by GSK are far clearer and a demonstrated 82% efficacy for Arevxy as compared to 67% for Abrysvo. Both vaccines work by stimulating an immune response against the Fusion protein (the F of the PreF and F3) that allows the virus to fuse to a host cell (yours!) and release genomic RNA into it. Blocking this protein prevents the virus from infecting cells. The vaccines themselves are expected to last over several seasons, although the observed efficacy of each declines over
time. For example, Arevxy dropped from 82% to 56% from Season 1 to Season 2.

Seasonal trends are not difficult to discern in this CDC graph beginning December 2021 and extending through in the last week of November 2023 (Figure 5 below).

Antigen Detections and PCR Detections: RVS, United States December 2021 through November 2023

RSV seasonality is typically November through March in the United States although in 2022 cases began an upward trend in September, before peaking in mid-November. Cases began trending upwards later in 2023 with the first rise occurring in October. Cases are far lower now than they were this time last year.

Paxlovid Rebound

I have been a proponent of Paxlovid administration for acute COVID since it first came on the market. There are a couple of reasons for this. Firstly, Pfizer trials have shown that Paxlovid administration within 5 days of symptoms reduced hospitalization and death by 86% amongst unvaccinated patients. Secondly, a September 2022 CDC study showed a 51% lower hospitalization rate within 30 days of infection amongst those who had received a primary mRNA vaccine series and at least one booster. Lastly, a VA study showed a nearly 30% risk reduction in long COVID for those patients who received Paxlovid as compared to those that did not (link: https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2802878).

However, it had long been my experience that COVID rebound associated with Paxlovid treatment (defined as a recurrence of symptoms and receiving a positive test after having the disease and then testing negative) was far higher than initial manufacturer estimates. Whereas Pfizer estimated a rebound rate of 2.3% with Paxlovid, a recent study published November 13th, (link: https://www.acpjournals.org/doi/10.7326/M23-1756) found that 20.8% of patients treated with Paxlovid experienced a rebound as compared to 1.8% of those receiving placebo.

The 20.8% is remarkably close to the rebound frequency we have seen here at Santa Monica Primary Care. Of 121 patients we have treated with Paxlovid, 24 (19.8%) reported a clinical rebound, typically about two weeks after treatment, Interestingly, rebound phenomenon appeared to cluster in our experience (Figure 6 below).

Paxlovid Rebound  Percent (%) by Month: Santa Monica Perimary Care,  2022-2023

The highest rates of rebound were seen in the Spring and Summer of 2022. During this time BA.1, BA.1.1 and BA.2 followed by the KBB sublineages of Omicron emerged. As compared to its Delta predecessor, Omicron multiplied 70 times faster in lung tissue but led to less severe disease. Perhaps rebound frequency is related to the circulating variant. In 2023, we had generally good results with Paxlovid with no reported rebounds until recently we have seen them reoccur in the months of July and October.

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