1/ Covid (@UCSF) Chronicles, Day 357
I’ve taken a little break from my threads – Covid is slowing down (yippee!) & I’ve gotten busy hosting @inthebubblepod. Thanks for your patience.
Today, I’ll update numbers, take a deeper dive into new CDC recs, & cover a few odds & ends.
I’ve taken a little break from my threads – Covid is slowing down (yippee!) & I’ve gotten busy hosting @inthebubblepod. Thanks for your patience.
Today, I’ll update numbers, take a deeper dive into new CDC recs, & cover a few odds & ends.
2/ @ucsfhospitals, marked improvement. Today, 18 pts, 4 on vents (Fig L). (On 1/12, #s were 102/24.) Test positivity also way down: now 0.7% overall – 3% in pts w/ symptoms, 0. 4 in pts w/ no symptoms (Fig R). Thus, asymptomatic person in SF has ~1-in-250 chance of having Covid. 
3/ Keep this low prevalence in mind in considering safety of activities. Remember, chance of catching Covid not only relates to riskiness of activity (eating inside, going to gym, etc) but also to odds that nearby person has Covid. Based on UCSF, it’s pretty low in SF right now.
4/ SF also good: 47 cases/d (vs 375 in Jan; Fig L). Hospitalizations also 47 (was 259 at peak in Jan; Fig R). Test positivity= 1.1%. Total of 436 deaths = 49 deaths/100,000 people.
A few comparisons: NYC: 354/100K; LA: 220; Miami: 207; Chicago: 194; Dallas: 136; Houston: 113.
A few comparisons: NYC: 354/100K; LA: 220; Miami: 207; Chicago: 194; Dallas: 136; Houston: 113.
5/ SF may well reach the end of Covid w/ <500 deaths. If U.S. had SF’s per capita death rate, we would have suffered 162,000 deaths, instead of 526,000.
In other words, 364,000 Americans would be alive today if the U.S. mirrored SF’s Covid mortality rate. Lots to be learned.
In other words, 364,000 Americans would be alive today if the U.S. mirrored SF’s Covid mortality rate. Lots to be learned.
6/ U.S. & CA trends also comforting (note: CA’s winter spike was mostly in SoCal.) Reassuring given growing frequency of CA variant – recent studies indicate it’s only modestly more infectious. Note that, w/ far higher rate of prior infection, SoCal is more “immune” than NorCal.
7/ While TX mask decision is unforgivable, it’s worth noting that – despite more lax approach in TX & FL than CA – case curves are similar (Fig). That said, CA’s death toll is significantly lower:
CA: 138 deaths/100K
FL: 148/100K (7% higher than CA)
TX: 158/100K (14% higher)
CA: 138 deaths/100K
FL: 148/100K (7% higher than CA)
TX: 158/100K (14% higher)
8/ The vaccine roll-out has turned from scandalous (in Dec/Jan) to impressive. We'll soon hit 100M doses given, now averaging >2M doses/day. 76% of distributed vaccines have been injected. The bottleneck now is supply – this should improve soon w/ addition of the J&J vaccine.
9/ Importantly, % of population that now wants vaccine has jumped – now 69%, vs 51% in Sept. In communities of color, rise has been particularly steep (61%, up from 42%). Equity problem is more one of accessibility of sites/scheduling than of attitudes.
pewresearch.org/science/2021/0…
pewresearch.org/science/2021/0…
10/ Meanwhile, % hesitant Republicans up (Dems 83% intend or have rec’d; vs 56% Repub), driven by misinformation campaigns from right-wing media & foreign countries. Another thing I’ll never understand about Trump: he & Melania were vaccinated without fanfare before they left WH.
11/ Trump should be basking in the glory of vaccination campaign (Operation Warp Speed was arguably the most important success story of his administration). Yet he, & other Republicans, have chosen to stay stay silent or even go anti-vax. Another missed opportunity to save lives.
12/ The quickening pace of the vaccine rollout means that, while we’re still far from herd immunity, we now have enough population immunity to exert a significant downward pressure on cases. The U.S. began w/ 100M people w/ prior Covid. Now add 92M doses injected (some have…
13/ …rec'd both doses, some 1 dose) & avoid double-counting those w/ prior Covid (who already had immunity, though vaccine will render it more durable). This get us to ~150M people w/ significant immunity (vaccine & infection-induced), or ~60% of adults; 45% of total population.
14/ But what about the variants! New @NEJM study showed that main variants of concern respond to antibodies formed after Pfizer vaccine. This, plus the relatively muted growth in the U.S. of the potentially vaccine-resistant strains (So. Africa, Brazil)…. nejm.org/doi/full/10.10…
15/ … offers even more grounds for optimism. While UK strain is, as expected, becoming dominant in U.S., the UK cases are falling more rapidly than U.S. (albeit w/ more consistent public health measures & higher % vaccinations) – more evidence that we can defeat the variants.
16/ I’m pleased that @CDCgov released its post-vaccination guidelines – as discussed @inthebubblepod podcasts.apple.com/us/podcast/too…, there are lots of things that folks can do post-vaccination. Saying that nothing should change doesn’t offer a lot of motivation to the vaccine hesitant…
17/ …(tho I’d hope that quashing risk of death would be sufficient incentive). I think CDC got it right, but it’s tough to make recs for an entire population when the issues are quite nuanced. To illustrate, let's work through a back-of-envelope example.
cdc.gov/coronavirus/20…
cdc.gov/coronavirus/20…
18/ Take the rec that it’s OK for vaccinated people to have indoor dinner w/ unvaccinated people in a home, unmasked. Based on UCSF’s asymptomatic case-positivity rate, let’s say that (in SF; odds may be higher elsewhere), there’s a ~1/250 chance that any one person is infected.
19/ OK, let’s consider a scenario from perspectives of both a vaccinated & unvaccinated participant. The vaccinated person is extremely protected – c/w unvaccinated, she/he has 72%-95% lower odds of Covid. Overall household Covid attack rate is ~17% so... jamanetwork.com/journals/jaman…
20/…the risk of a single encounter must be less – let's guess (no good data) it's ~3%. Taking odds of asymptomatic infection (0.4%) x 3% usual transmission risk from encounter, then cut odds by 72-95% w/ vaccine. My math says 1 in ~60,000 chance that vaccinated diner gets Covid.
21/ Low enough? To me, yes, since there’s zero chance of getting super sick & dying. One caveat: we’re not completely sure that mild Covid can’t lead to Long Covid. Odds must be very low; so I'd guess there's a 1 in ~300,000 chance of a regrettable outcome from dinner. I'd do it.
22/ How about the risk to the unvaccinated dinner guest? If the asymptomatic, unvaccinated dinner guest in SF has a 1/250 chance of having Covid, the vaccinated person has 72-95% lower odds, so maybe 1/2000. (I've simplified, since 1/250 includes some vaccinated folks. But you...
23/…get the idea.) Emerging data from Israel & Moderna point to ~60-80% reduction in chance of a vaccinated person transmitting the virus. If usual odds of dinner transmission are 3% & vaccination drops it by ~2/3rds, then ~1%. Ergo, odds of vaccinated person infecting his/her…
24/…dinner guest would be ~1 in 200,000. Again, pretty darn low & I'd be in for dinner. Unless…
...the guest was at sky-high risk of bad outcome, such as over age 75 (~200-fold higher risk of death than a 25-year-old). In that case, not worth it.
Which is where CDC landed.
...the guest was at sky-high risk of bad outcome, such as over age 75 (~200-fold higher risk of death than a 25-year-old). In that case, not worth it.
Which is where CDC landed.
25/ Despite complexity, CDC's job is to offer simple guidance for all. Above reflects their process in making recs.
Thx for reading. I’ll keep doing threads ~weekly as long as they seem useful. For the 1st time in a year, I can see a time when news will be good enough to stop.
Thx for reading. I’ll keep doing threads ~weekly as long as they seem useful. For the 1st time in a year, I can see a time when news will be good enough to stop.
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