…then Rick drops the mic :-)
> On Aug 12, 2021, at 4:18 PM, basfa-requ...@lists.basfa.org wrote: > > Send Basfa mailing list submissions to > basfa@lists.basfa.org > > To subscribe or unsubscribe via the World Wide Web, visit > http://lists.basfa.org/listinfo.cgi/basfa-basfa.org > or, via email, send a message with subject or body 'help' to > basfa-requ...@lists.basfa.org > > You can reach the person managing the list at > basfa-ow...@lists.basfa.org > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of Basfa digest..." > > > Today's Topics: > > 1. Re: BBQ party for the vaccinated, West Menlo, Saturday, Aug. > 14, 4pm-12m (Rick Moen) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Thu, 12 Aug 2021 03:05:31 -0700 > From: Rick Moen <r...@linuxmafia.com> > To: basfa@lists.basfa.org > Subject: Re: [Basfa] BBQ party for the vaccinated, West Menlo, > Saturday, Aug. 14, 4pm-12m > Message-ID: <20210812100531.gb19...@linuxmafia.com> > Content-Type: text/plain; charset=utf-8 > > Quoting Jonathan Del Arroz (jdelar...@gmail.com): > >> I?ll just host a party for the unvaccinated instead, since studies are >> showing we spread the new variants less, anyway. Mine should be safer! > > Nope. Your knowledge of epidemiology needs repair, Jon, as you've > been misinformed. > > There _aren't_ "studies" showing that unvaxed spread Delta and > successors less. That is wrong twice over: Unvaxed are massively more > likely to get infected at all, and also massively more likely to remain > infectious for longer periods, lengthening potential exposure. > > What actually came out wasn't a study, but rather a brief item in the > Aug. 6 edition of CDC's _CDC Morbidity and Mortality Weekly Report_ > (MMWR) covering a Delta outbreak at Provincetown, tip of Cape Cod, after > Independence Day. Social media glommed onto _one_ figure: among 469 > PCR-confirmed COVID-19 infections found among seaside party-goers, 346 > (74%) occurred in vaccinated persons. Also, breakthrough (vaxed) infectees > during their period of infectiousness carried about the same viral load > as did the unvaxed infectees (the same "cycle threshold" aka Ct, during > operational cycles of the machine that does PCR testing to detect and > duplicate viral genetic material). So, whoa! Being vaxed means you > spread Delta _more_, right? > > Nope. This falls haplessly into Base Rate Fallacy, where you flub > estimating probability by ignoring context. > > To understand that, imagine a slightly inattentive researcher studying > alcoholism in Dad's hometown of Kristiansund, population ~25,000. > > Say (not real numbers here, but credible ones) results note that out of > 550 identified alcoholics, 542, were blond. Whoa, says he! If you're > blond and resident of Kristiansund, you've 97% chance of alcoholism. > We must search for genetic links. > > Does this researcher get a Nobel? Nope, he gets indulgent chuckles, > as he forgot Kristiansund (north of Bergen) has wall-to-wall blonds, > about as many blonds as herrings. Call that, in round figures, 22,000. > So, more like a 542 / 22000 * 100 = 2% chance, not 97%. > > Getting back to Provincetown: That 74% is just wildly devoid of base > rate context, in that the study of the outbreak made no estimate of how > many persons got exposed, nor even what percentage of those present > in total were vaxxed. The 469 infectees were essentially self-reported > people, concerned enough to get PCR-tested. Nobody got told "We need to > test you if you were in any Provincetown bar between July 10th and 18th": > Thus, there's an automatic "detection bias". Second, as vaxed > population has increased, especially among people like Cape Cod > holidayers, you get the Kristiansund-blonds problem: Vaxed persons > necessarily will then constitute a rising portion of cases. > > For all of the above reasons plus others I don't even get into, _MMWR_ > warned the info was "insufficient to draw conclusions about the > effectiveness of COVID-19 vaccines against SARS-CoV-2". But social > media ignored that, and stumbled straight into the Base Rate Fallacy > trap. https://www.snopes.com/fact-check/cdc-provincetown-covid-event/ > https://www.snopes.com/ap/2021/07/30/study-vaccinated-people-can-carry-as-much-virus-as-others/ > > As a statistics guy and a Bayesian, that kind of thing makes me sad. > > Also, with Delta as with prior variants, vaxed infectees clear virus faster. > https://www.cdc.gov/coronavirus/2019-ncov/variants/delta-variant.html > https://www.technologyreview.com/2021/08/09/1031292/questions-delta-variant-contagious-tranmission-vaccination/ > > -- > Cheers, "Orthodoxy is my doxy. Heterodoxy is someone else's doxy." > Rick Moen -- William Warburton, Bishop of Gloucester (1698-1779) > r...@linuxmafia.com > McQ! (4x80) > > > ------------------------------ > > Subject: Digest Footer > > _______________________________________________ > Basfa mailing list > Basfa@lists.basfa.org > http://lists.basfa.org/listinfo.cgi/basfa-basfa.org > > > ------------------------------ > > End of Basfa Digest, Vol 173, Issue 4 > ************************************* _______________________________________________ Basfa mailing list Basfa@lists.basfa.org http://lists.basfa.org/listinfo.cgi/basfa-basfa.org
