she completely screws up a back of envelope calculation on how many deaths might happen before we get to herd immunity. She starts out correctly: if you use the standard “threshold theorem” <\/span>1<\/sup><\/a><\/span> , you conclude that roughly 65% of the people (roughly 215,000,000) need to be infected and become immune before you get to herd immunity. <\/p>\n\n\n\n And then she goes completely off the rails. She says there are about 6.6 million confirmed cases of Covid-19 with about 200,000 deaths, so there is a case fatality rate of about 2.97% based on the total number of cases (roughly 200,000\/6,600,00). That’s correct. And then this graphic shows up:<\/p>\n\n\n\n What she is doing here is taking the case fatality rate and multiplying it by the number of cases you would (roughly) need to have herd immunity. The problem is that you need to use the infection fatality rate <\/em>not the case fatality rate in any calculation like this. And, because there are many many cases of Covid 19 that we don’t know about than those we have found through testing, these two numbers are very different. The infection fatality rate is much much lower. Why didn’t she check with Ashish Jha or Michael Osterholm who would have caught this horrible mistake? The good guys aren’t supposed to go so badly off the rails.<\/p>\n\n\n\n Look anyway you cut it, as I will shortly show you, the number of deaths is beyond horrible. <\/em> But using the case fatality rate rather than the infection fatality rate means the number of deaths is too high by at least a factor of 3 – and that is absent any therapeutic changes which she correctly points out later would lower this number. <\/p>\n\n\n\n So what was her mistake? Well, the 6.6 million confirmed cases are just the tip of the iceberg. Based on antibody testings (and of course the test positivity ratios we have seen) the best estimates of the number of infections in the United States I have seen say there are between three and twelve times the number of infected people as there are confirmed cases i.e. roughly between 20 and 80 million people have actually been infected by Covid 19. Using these numbers you get an infection fatality rate of between .25% (200,000\/80,000,000) and 1% (200,000\/20,000,000). Anthony Fauci thinks that the infection fatality rate is actually the higher number i.e. about 1%, so I will use this number. This rate gives us (absent any therapeutic changes that greatly lower the death rate) 2.15 million deaths (1%*215,000,000) before herd immunity occurs at the high end with Fauci’s estimate and about 550,000 at the low end if the infection is far more widespread than testing would indicate.<\/p>\n\n\n\n So, the situation is beyond horrible in both cases – if we take the herd immunity route, but let’s not do the math wrong – it gives ammunition to the bad guys.<\/p>\n","protected":false},"excerpt":{"rendered":" I love back of envelope calculations and I love Rachel Maddow, she is so bright and usually does her homework. Yesterday, not so much. In this segment: http:\/\/www.msnbc.com\/rachel-maddow\/watch\/math-on-trump-covid-strategy-has-millions-dying-before-it-works-91958341539 she completely screws up a back of envelope calculation on how many deaths might happen before we get to herd immunity. She starts out correctly: if you … Continue reading “Alas the usually awesome Rachel Maddow doesn’t do the math for herd immunity right”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[6],"tags":[],"class_list":["post-529","post","type-post","status-publish","format-standard","hentry","category-the-pandemic"],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/garycornell.com\/wp-json\/wp\/v2\/posts\/529","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/garycornell.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/garycornell.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/garycornell.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/garycornell.com\/wp-json\/wp\/v2\/comments?post=529"}],"version-history":[{"count":6,"href":"https:\/\/garycornell.com\/wp-json\/wp\/v2\/posts\/529\/revisions"}],"predecessor-version":[{"id":538,"href":"https:\/\/garycornell.com\/wp-json\/wp\/v2\/posts\/529\/revisions\/538"}],"wp:attachment":[{"href":"https:\/\/garycornell.com\/wp-json\/wp\/v2\/media?parent=529"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/garycornell.com\/wp-json\/wp\/v2\/categories?post=529"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/garycornell.com\/wp-json\/wp\/v2\/tags?post=529"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\"\"](\"https:\/\/garycornell.com\/wp-content\/uploads\/2020\/09\/maddow-1-2.png\")
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