Bob Wachter Profile picture
Apr 4, 2021 25 tweets 8 min read Read on X
1/ Covid (@UCSF) Chronicles, Day 383

Perhaps the most confusing time since the start of the pandemic – its easy to be overwhelmed. I’ll try to make sense of some of the key trends, particularly the “4th surge” & vaccines vs variants.

Bottom line: I’m still leaning optimistic.
2/ Part of my optimism stems from where I live: Covid stats in San Francisco are excellent. Let’s start w/ @UCSFHospitals, where there are 7 Covid pts (vs. ~100 in January), & only one on a vent (Fig L). Test positivity is 0.9%; 0.4% in asymptomatic patients (R). Pretty darn low. ImageImage
3/ SF overall is also good: 37 cases/day in city of 875K, maybe a tiny uptick in past few days (Fig L). Only 21 Covid pts in all SF hospitals (vs. 259 in January; R). And only 6 Covid deaths in SF in past 4 weeks; total deaths remain <500 for pandemic. Test positivity also 0.9%. ImageImage
4/ Why such good control in SF? It's partly behavior: most still masking; indoor dining open @ 50%. And 48% of SF adults have rec’d one shot; 27% are fully vaxxed. (U.S. avg: 31% one dose; 18% both) We have variants, but mostly West Coast one – bad, but not as bad as UK variant. Image
5/ In regions w/ surges (Michigan, Northeast), it’s likely that some combo of these factors are at work: people lowering their guard, opening of high-risk settings too soon, lower vaccination rates, & higher prevalence of UK variant. Hardest hit places have more of these at play.
6/ The variants are scary but beatable – through remaining careful & by vaccination (which works well against variants currently in U.S., mostly UK's B117). Plummeting case rates in UK & Israel (Fig) offer vivid evidence that UK variant can be defeated by widespread vaccination. Image
7/ Note: U.S. isn’t far behind UK in vaccine doses given – U.S. has given enough vax for 24.9% of population; UK 27.4%. Why is Covid falling faster there: a) they’ve (smartly) opened more slowly, & b) they’ve employed delayed 2nd dose strategy, having vaccinated 47% of populace…
8/ … with one shot, but only 8% with two shots. Conversely, U.S. has stuck w/ on-time 2nd dose strategy: 31% have rec'd one dose, 18% both. I still believe UK made the better call: we now know that one dose is 80% protective – so UK got more people protected faster than we did.
9/ Why am I optimistic despite our regional upticks? Because virtually all we've learned about the vaccines is phenomenal. First, we now know that their efficacy in real world settings matches that seen in clinical trials: ~90%.… That's astoundingly good.
10/ AND we know that the earlier question – namely, does vaccination cut the risk of asymptomatic transmission? – has been answered: Yes! That's great news.….

AND we know that near-perfect vaccine protection vs. hospitalizations & death remains true in…
11/ …real world settings. AND that our vaccines appear to work just fine, thank you, against the variants that we’re actually seeing in U.S. AND that our vaccination pace has skyrocketed to ~2.5-3M/day. AND that the three vaccines that we’re using in the U.S. are completely…
12/ … safe, both in terms of short-term side effects/ allergies, & long-term effects.

(Parenthetically, this piece @TheAtlantic… on AstraZeneca clotting issue is worth reading – while “blood clots” are common, the syndrome of low platelets & widespread…
13/ …clotting is not, so I’d guess that this is in fact a rare side effect of AZ vaccine. The benefits of getting vaccinated still far outweigh this tiny risk, but it's a nail in the coffin for AZ’s efforts to be part of the U.S. arsenal, since we’ll have enough vax without it.)
14/ AND finally, we’re seeing rising numbers of people who want to be vaccinated… ; no longer big differences between whites & communities of color. Now it seems that it's mostly Republicans choosing to forego vaccination. The White House is rolling out…
15/ …a vigorous campaign to promote vaccination in various groups (Walensky’s “Doom” speech was likely part of it).

Once vaccination is fully/equitably available to all (in next 6-8 wks), if someone chooses to forego their shot that’s a personal choice...but it’s an awful one.
16/ Because here’s how I think about Covid in the U.S. today:

In 2020, we were all at risk, but some were at higher risk of getting Covid due to exposure (job or living circumstances, +/- behavior) or at higher risk of dying from Covid due to age/comorbidities/access to care.
17/ While the traditional categories related to risk of exposure & death are still meaningful, today we need to divide the population into three different groups:

a) Fully vaccinated
b) Partly immune (via partial vaccination or prior infection), &
c) Unprotected.
18/ Fully vaccinated folks can live pretty large, as @CDCgov has signaled in their new guidance about get-togethers & travel. Even with variants growing, the protection against getting Covid, transmitting it, & particularly against getting very sick & dying is truly impressive.
19/ Partly immune folks are safer, but they should still be careful. Even if you’re ~80% protected via your first mRNA shot or via prior infection (Denmark study: ~80% protection from prior infection, but only ~50% in those >65…), the variants are so much…
20/ …nastier (B117: ~60% more infectious & ~60% deadlier) that their risk is still very real.

For these folks: finish vaccination as soon as you can; it still seems likely that those w/ prior infection may only need 1 shot of mRNA vax, but that’s not yet endorsed by FDA/CDC.
21/ (I know that some may cry hypocrisy when I recommend that partly vaccinated folks get 2nd shot ASAP, while also promoting delayed 2nd shot strategy. It’s the difference between individual vs public health. As an individual, it’s better for you to finish both shots fast, but…
22/ … as a society, we’d be better off if more people got first shots sooner. Another reason why life as a public health official is so impossibly tough.)

And finally, the third group is the unvaccinated. If anything, they're at higher risk than at any time in the pandemic…
23/ …since they remain completely vulnerable to SARS-CoV2 generally & now face a variant that's even more infectious & deadly. Moreover, due to Covid fatigue and/or misguided messaging, many are acting less safely. If there’s a fourth wave, this is the group that'll be hammered.
24/ A saving grace is that, on avg, they're younger & healthier than folks who've been vaccinated. The bad news: with large numbers of infections, plenty of them will still get sick & some will die, and their infections will fuel higher rates of transmission & thus more variants.
25/ So it could go either way: a virtuous cycle if folks stay careful & get vaccinated. A vicious one if folks act unsafely or don’t get jabbed. Worst case: more vaccine-resistant variants.

Taken as a whole, I’m still optimistic. But you can see why it’s so darn confusing. /end

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More from @Bob_Wachter

Dec 18, 2023
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) Image
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)
Read 25 tweets
Aug 18, 2023
Covid (@UCSF) Chronicles, Day 1249
While good data are far harder to come by than in the past, it’s clear that we’re experiencing another Covid uptick. Today: what that means and how you might choose to alter your behavior in response. (1/25)
First, the evidence for the uptick (I don’t say “surge” since I associate that with the massive surges of the past):
This curve of hospitalizations (a reasonable proxy for the amount of Covid in the community) shows a definite, but relatively mild, upward trend. (2/25) Image
Alas, one can't look at any single measure to quantify an uptick anymore. But all arrows now point in the same direction: up (⬆ wastewater,⬆ hospitalizations,⬆ deaths,⬆test positivity). Even my fave measure, @UCSFHospitals’ asymptomatic test positivity rate, is no… (3/25)
Read 25 tweets
Jul 13, 2023
Until this week, I remained a NoVid, which I chalked up to being fairly cautious, fully vaxxed & a bit lucky.
This week my luck ran out. My case is a cautionary tale, particularly for the “just a cold” folks. Mine definitely was not...I literally have scars to show for it. (1/22)
I’ve got my 2nd bivalent in April, so my protection against a severe case was still strong, but the 2-3 month window of protection vs. getting Covid had passed. I've let down my guard a bit: still masking on planes & in crowded rooms, but I do now eat and drink indoors. (2/22)
This week, I was on clinical duty @UCSFHospitals. We are still required to mask in patient areas (good!). I felt fine until Sunday afternoon when, after leaving the hospital, I noticed a dry cough. By Sunday night, I felt flu-ish, with a sore throat, fever, and chills. (3/22)
Read 22 tweets
May 23, 2023
Covid (@UCSF) Chronicles, Day 1161
With the Pub Health Emergency over, it's a good time to update you on my view of Covid & my current approach to Covid behavior – which is now based on 2 principles:
1) Is the risk worth it?
2) Can I live w/ the behavior for the long haul? (1/25)
First, let’s review today's situation. Since Omicron's emergence in 11/21, the biggest surprise has been the absence of surprises. Yes, we’ve seen a few variants that led to mild surges, but we haven’t had to interrogate our Greek dictionary for a new letter for 18 months. (2/25)
mRNAs still work great in preventing severe infection, and Paxlovid, home tests, & ventilation still work well too. Long Covid remains a concern, but we know that both vax & Pax lower its frequency, that most (though definitely not all) folks… (3/25)…
Read 25 tweets
Feb 17, 2023
Important @TheLancet systematic review finds Covid infection confers robust & long-lasting (good at 40 weeks) protection vs both symptomatic & severe Covid infection.(Weaker w/ Omicron, but still good.)…
How will results influence my behavior/thinking?(1/7)
a) I've been considering a Covid infection to be the equivalent of a booster in terms of protection against reinfection & severe disease (hospitalization/death). These study results indicate that it is at least that good, maybe even a bit better... (2/7)
b) We've been headscratching about why XBB variant didn't cause more of a surge, despite low uptake of the bivalent booster. It may be that immunity from all those 2022 Omicron infections kept it at bay (that's informed speculation – Lancet study ended before XBB spike)... (3/7)
Read 7 tweets
Jan 19, 2023
Covid (@UCSF) Chronicles, Day 1038
Some folks continue asking what I'm doing viz Covid behavior...
Answer: I'm changing my behavior. In the Bay Area, I'm now OK with indoor dining & removing my mask for small group gatherings.
I haven't changed, the risk has. Here's how: (1/25)
Specifically, I haven't changed my perspective on balancing prudent caution with everyone's (including my) desire for "normal."
But, in the Bay Area at least, the Covid risk has come down considerably, and, by my way of thinking, this allows for a more permissive approach.(2/25)
Where I'm coming from:
1) I'm 65 & haven't had Covid
2) I want to live as fully as I can, but am comfortable taking reasonable steps to avoid infection
3) I'm fully vaxxed & had bivalent in Sept
4) My main fear is Long Covid, which I peg at ~5% probability per Covid case. (3/25)
Read 25 tweets

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