Having trouble understanding SF's strategy around masking—not sure what "slowing the spread" achieves this time absent other programs. Help me steel-man?
Buying time for vaccination? 84% eligible got 1+ vaccine; ~3wks to rise from 83%; now 500 ppl/day of 126k eligible. :/
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Maybe: buying time for the ~10% of vaccinated residents who have only received one dose of their two-dose series? That could have a bigger impact in the short/medium-term than waiting for more 0->1 recipients.
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Maybe about scaling the expo to avoid hospital overflows? The SFData hospital capacity tracker stopped updating on 07/21, but this could conceivably make sense, given that hospitalizations will probably reach (at least) their January peak.
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Or is it about buying time for vaccine approval for < 12 y.o.s? I haven't heard public health officials express this argument, but on its face it makes more sense than the others. Data doesn't support this driving the decision, though: only ~7% of cases are <12 (and falling)
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Masking could make a lot of sense if coupled with some other policy which actually has an end-game: perhaps they'll shortly announce proof-of-vaccination/test requirements for restaurants and other public venues? Then you're buying time for accelerated vaccinations.
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Or: buying time to get housing programs going for the unhoused? Data doesn't really support this as a driving force; only ~1% of cases are among people experiencing homelessness.
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To be clear I'm not disputing virulence / danger here! Keeping people from getting sick is good! I'm confused because R0 is high enough that we're stuck with exponential spread in the medium-term; without other policies, I don't see how this changes the total area under curve.
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(I do wish would explain the strategy in technical form! I'm sure they have memos, analyses, etc. Probably they don't share because it would create lots of noise/confusion/support-burden, but I wish we could just read the "real" reasoning!)
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Following up: the hospital overflow scenario seems unlikely to be the driving force here; even in the January peak COVID patients represented only ~11% of SF hospital beds:
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Furthermore, even during the highest peak in the Bay Area, none of our hospitals ever reached more than 64% full.
Beyond that, COVID patients never represented more than 11% of our total hospital capacity.
And that was _before_ most people were able to get vaccinated.
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Very interesting! CDC model's finds that vaccinated masking is sufficient to drop R (currently ~1.34) < 1 at our vaccination coverage % (but unvaccinated masking is not). This is a much greater effect than I expected and justifies the policy if true. washingtonpost.com/context/cdc-br (p20)
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In March (!) a CADPH study found that 29% of Bay Area residents had antibodies, which means the right column of plots is more relevant to us. Surprised our R is so high given that—maybe this model is too optimistic.
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Slowing the spread means it will stabilize closer to the herd immunity level rather than wildly overshooting it.
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See this thread for a more detailed explanation.
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4. The main point in the original thread was that if herd immunity requires 60% of the population to be infected, you can't just let the epidemic go unchecked and expect to suffer "only" 60% infected. This is because of something known as overshoot. Let's take a look.
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