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This is: The Case for Extreme Vaccine Effectiveness, published by Ruby on the LessWrong.
I owe tremendous acknowledgments to Kelsey Piper, Oliver Habryka, Greg Lewis, and Ben Shaya. This post is built on their arguments and feedback (though I may have misunderstood them).
Update, May 13
I first wrote this post before investigating the impact of covid variants on vaccine effectiveness, listing the topic as a major caveat to my conclusions. I have now spent enough time (not that much, honestly) looking into variants that I have a tentative position I'm acting on for now.
My moderately confident conclusion is that the current spread of variants in the US barely impacts vaccine effectiveness. The Pfizer vaccine is reported to be 85% as effective against the feared B.1.351 variant (South African) as it is against B.1.1.7 (UK). Assuming that other variants are no more resistant than B.1.351 on average (a reasonable assumption) and that presently variants are no more than 25% of Covid cases (in Alameda and San Francisco). The net effect is 0.250.85 + 0.751.0 = 0.9625. In other words, vaccines still have 96% of the effect they would if B.1.1.7 were the only variant.
Plus, that tiny reduction of vaccine effectiveness is dwarfed by the falling background prevalence of Covid. When I first wrote this post, Alameda and San Francisco were at 0.1-0.15%; now they're at ~0.05%. The same for New York and the United Kingdom.
Although relaxing of restrictions might reverse this, right now, Covid-risk is very, very low in the Bay Area and many parts of the US.
All updates/changelog can be viewed here.
I plead before the Master of Cost-Benefit Ratios. “All year and longer I have followed your dictates. Please, Master, can I burn my microCovid spreadsheets? Can I bury my masks? Pour out my hand sanitizer as a libation to you? Please, I beseech thee.”
“Well, how good is your vaccine?” responds the Master.
“Quite good!” I beg. “We’ve all heard the numbers, 90-95%. Even MicroCOVID.org has made it official: a 10x reduction for Pfizer and Moderna!”
The Master of Cost-Benefit Ratio shakes his head. “It helps, it definitely helps, but don’t throw out that spreadsheet just yet. One meal at a crowded restaurant is enough to give even a vaccinated person hundreds of microCovids. Not to mention that your local prevalence could change by a factor of 5 in the next month or two, and that’d be half the gains from this vaccine of yours!”
I whimper. “But what if . . . what if vaccines were way better than 10x? What about a 100x reduction in the risks from COVID-19?”
He smiles. “Then we could go back to talking about how fast you like to drive.”
In its most extreme form, I have heard it claimed that the vaccines provide 10x reduction against regular Covid, 100x against severe Covid, and 1000x against death. That is, for each rough increase in severity, you get 10x more protection.
This makes sense if we think of Covid as some kind of "state transition" model where there's a certain chance of moving from lesser to more severe states, and vaccines reduce the likelihood at each stage.
I think 10x at multiple stages is too much. By the time you're at 1000x reduction, model uncertainty is probably dominating. I feel more comfortable positing up to 100x, maybe 500x reduction. I dunno.
There is a more limited claim of extreme vaccine effectiveness that I will defend today:
In the case of the Pfizer vaccine (and likely Moderna too), the effectiveness in young healthy people is 99% against baseline symptomatic infection, or close to it.
We can reasonably expect the effectiveness of the vaccine against more severe cases of Covid to be greater than effectiveness against milder cases of Covid.
(Maybe it's 2x more effective against severe-Covid and 3x more effective against death compared to just getting it at all. Something lik...
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