Thread by @Bob_Wachter

Covid (@UCSF) Chronicles, Day 1371
I haven’t X'ed much about Covid lately, mostly because things are fairly stable. But a lot of folks have asked me what I’m doing, Covid-wise.
So today: how I’m acting, & why. Graphic below shows my general approach; more details follow. (1/25)

How am I acting currently? Given a moderate uptick in Covid over the past two months, I’m back to masking in crowded and poorly ventilated places, particularly when I don’t need to talk. When I do mask, I always use an N95; I see no reason to wear a less effective mask. (2/25)

Examples of where I currently mask: crowded stores, airplanes or trains; elevators; and theaters. But given that today’s uptick is only moderate, I’m still OK with indoor dining (though will opt for outdoor if conditions allow) and for going maskless at holiday parties. (3/25)

To me, the most surprising thing about Covid for the past 18 months has been the lack of surprises: no game-changing new variant; vaccines, Paxlovid, and home testing still work well; Long Covid remains a threat. That said, there are a few things that are different. (4/25)

1) Whereas I used to try to precisely map Covid prevalence to guide behavior (the "5-10 cases/100K/d" threshold), today, with so little publicly reported testing, it’s impossible to be that precise. So I just aim to place the current Covid situation into one of 3 buckets…(5/25)

Low Risk: Cases low & stable (this is how it was two months ago)
Moderate Risk: Cases moderate and/or rising (how I see things currently)
High Risk: Bona fide surge (such as the one last winter)

2) I use 2 main metrics to put the current state into 1 of these buckets:...(6/25)

a. Wastewater numbers: I follow both CDC & Biobot
b. Hospitalizations in region (Calif:
(I'll also glance at test positivity rates, ER visits & death rates, but I don't rely on them as go-to metrics.) (7/25)cdc.gov/nwss/index.html
biobot.io/data/
cdph.ca.gov/Programs/CID/D…

3) Decision making re: boosters is fairly easy, especially for age >60. To me, studies are clear that staying up to date on vax lowers hospitalization, death, & Long Covid rates, with negligible risk. For elders, staying up to date shouldn't be controversial (yes, I know).(8/25)

Decisions for younger folks without medical co-morbidities are harder, mainly because their risk of a severe case is so low, even without boosting. However, even in people <60, I think that dropping the odds of Long Covid, & transiently (10 weeks or so) lowering the…(9/25)

… chance of getting Covid make getting boosted a good call.
But it’s not a slam dunk, the way it is in older people. If one of my 30ish-year-old kids decided not to get their next booster, I wouldn’t quibble much (though I'd still recommend it). (10/25)

4) Although Covid really hasn’t proven to be a seasonal virus (see @mtosterholm: ), my threshold for masking is lower in the winter because it will also thwart flu, RSV, and other viruses that can cause real harm. (11/25)cidrap.umn.edu/covid-19/episo…

5) While I’m glad that public health officials & scientists pay close attention to the Covid variant-du-jour, I don’t get too stressed over them – they often prove to be "scariants." For personal decision making, it’s reasonable to assume that there'll nearly always be… (12/25)

… an emerging variant that has a potential advantage over prior variants, & that could grow up to be a threat.(Today: JN.1, HV.1…)
But we really never know what a variant will do until it does it, so – from the standpoint of guiding personal behavior – I focus on the…(13/25)

... wastewater & hospital rates. If it’s a variant that's truly more infectious or immune-evasive, before long we’ll see its improved “fitness” reflected in the Covid prevalence stats. Until then, knowing that it’s out there doesn’t really change my choice of how to act. (14/25)

6) How much "credit" do I give a recent vax or case of Covid in terms of blocking transmission? A modest amount for ~10 weeks, during which there is some (~30-50%) protection vs. infection. So if there was a modest uptick in cases but I had either gotten a booster or… (15/25)

...had Covid in the past 10 weeks, I wouldn’t don my mask.
After 10 weeks, though, that infection or vax doesn’t really help block transmission (though it continues to lower the odds of a severe case & Long C), so I’m back to making decisions based on prevalence only. (16/25)

7) All of this is based on my personal status: a relatively healthy 66-year-old who doesn’t live with anyone vulnerable. I’d be more careful if I was 80, immunosuppressed, or living with someone in either of these categories. And I might be a bit less careful if I was 40. (17/25)

8) As per UCSF rules, I still mask when I’m seeing patients (as I’m doing this week). In non-patient care areas at work, I follow my general rubric: given today’s moderate uptick in cases, I'll generally mask in crowded indoor spaces when I don’t need to speak much. (18/25)

9) As for testing, I still home test if I have any symptoms that could be Covid, & before gatherings that include vulnerable folks. (For example, we tested before a recent small gathering that included an immunosuppressed friend.) I end up testing a few times each month. (19/25)

Against that background, here’s how I apply it to today:
In CA (Fig L), hospitalizations ~300/d, up from 225 in Oct. but far below last winter’s ~650/d. In SF (R): 40 hospitalized Covid pts, vs last winter’s ~150.
In U.S., wastewater is up, particularly in the Midwest… (20/25)

… and the South (overall U.S. on L, regions R), but not massively so.
So I’d deem the Covid situation (in CA at least; it’s somewhat worse in the South & Midwest) to be moderate – higher risk than the fall but not a bona fide surge. And I’d act accordingly, Covid-wise. (21/25)

As to other factors, there's more flu & RSV, which moves me toward more caution (ie, a bit to R on my graphic), particularly in terms of masking. On the other hand, I get no credit from either my case of Covid in July or my booster in Sept, since both are >10 weeks ago. (22/25)

So that's where I've landed today – in my moderate box, with a little extra caution due to seasonal viruses. This means I mask in theaters & crowded stores, but I'm ok maskless at indoor dining or parties – since that’s how I’ve chosen to act when Covid risk is moderate. (23/25)

The fundamentals of Covid risk assessment & prevention are the same today as they were last year, and will probably be the same 5 years from now. While we can’t be as precise as we once were, that's largely due to a marked decrease in the acute threat level, which is a…(24/25)

… good thing. I’ve found it useful to have rules of thumb that I can live with, now and, quite probably, for years to come. I hope mine are helpful to you as you develop your own strategy, influenced by your personal risk factors and preferences.

Enjoy the holidays! (25/end)