Bob Wachter Profile picture
Apr 4, 2021 25 tweets 8 min read Twitter logo Read on Twitter
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

May 23
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
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
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
Dec 27, 2022
I appreciate all (or, at least most) of the feedback on yesterday’s post regarding how I make decisions about Covid risks and mitigations, including my 50% Rule.
A brief follow-up thread today, with a few additional thoughts and responses: (1/12)
a) First, of course we’re entering year 4 (!) of Covid (I mistakenly said year 3 in yesterday's first tweet). Sorry.
I was hoping that by now Twitter would have added an edit function, but the new management seems focused on other changes. Hopefully at some point. (2/12)
b) A few folks asked how masking fits into my risk mitigation algorithm.
Just as I’m comfortable doing anything OUTSIDE without a mask, I’m OK in ALL indoor spaces – incl. crowded theaters, subways, etc. – wearing a KN95. I’m also OK removing my mask briefly to eat/drink. (3/12)
Read 12 tweets
Dec 25, 2022
Covid (@UCSF) Chronicles, Day 1013
As we enter Covid Year 3, it’s clear we’ll be in our current predicament for the foreseeable future. This means we all need to find our own method to weigh & mitigate risks.
Today I’ll describe my “50% Rule” & how it governs my choices. (1/25)
All of us make risk choices daily, without much thought. What is the chance of rain above which I’ll bring an umbrella? Do I buy flood or earthquake insurance? Do I take a statin for my cholesterol? In making these choices, it’s rare there’s an unambiguously “right” answer.(2/25)
Instead, we weigh the odds & badness of the thing we’re trying to avoid; how unpleasant, risky, & expensive the mitigation is; & our own risk tolerance. Since the cognitive burden of doing this for myriad choices daily is onerous, we all develop rules of thumb to guide us. (3/25)
Read 25 tweets
Dec 19, 2022
Covid (@UCSF) Chronicles, Day 1006 (!)
There’s an awful lot of Covid confusion & misinformation out there, particularly around these three topics: masks, vaccines, and home tests. Let’s look at them in today's thread. (1/24)
To start, these statements are correct:
• Wearing the wrong mask, or wearing a mask incorrectly, doesn’t work
• Vaccination/boosters don’t work as well as they used to in preventing infection
• Home tests yield more false negative results than they used to.
But these statements are unambiguously wrong:
• Masks don’t work
• Vaccines/boosts don’t work
• Home tests don’t work
This is confusing enough that it’s an easy mark for those who want to spread misinformation. Here’s how I interpret the science to inform my decisions: (3/24)
Read 24 tweets

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