Again: Viruses do not necessarily evolve to be milder—especially if they transmit early, like this one. Our immune system learning about it—via vaccines or infection—can mean better response next time, so milder experience. Not same as virus becoming intrinsically less virulent.https://twitter.com/zeynep/status/1465075561236250631 …
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Replying to @zeynep
This is a bold statement to make while we wait on omicron reinfection severity data. If a variant is sufficiently different, immunity from previous infection may not be effective. Consider how norovirus keeps causing the same gastro symptoms for all ages with each reinfection.
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Replying to @lisa_iannattone @zeynep
Just as there are many noroviruses and immunity from one doesn’t translate to immunity to another, immunity to one SARS2 virus may not translate to immunity to a sufficiently different SARS2 virus. We’re far too early in the course to be as certain about this as you seem to be.
2 replies 3 retweets 33 likes -
Replying to @lisa_iannattone
zeynep tufekci Retweeted zeynep tufekci
Not a bold statement. Everything else equal, of course re-infections are milder *on average*. We have so much data on this now. Two, as first tweet explains, a new variant is not everything else equal, so can be *more* severe to people with no immunity.https://twitter.com/zeynep/status/1465075561236250631 …
zeynep tufekci added,
zeynep tufekciVerified account @zeynepThis is a myth. Especially for a virus that can transmit early in disease course, like this one, selection pressure is on transmission, not virulence. So a new variant can be MORE or LESS virulent (when everything else equal, i.e. host immunity). https://twitter.com/soccervolleymom/status/1465074442044850183 …Show this thread3 replies 1 retweet 9 likes -
Replying to @zeynep
There’s actually not much data on severity of reinfections and much of the data we have doesn’t suggest a milder course for all. We could just as easily say primary infections are mild on average but the avg isn’t the story. The small % of a large number = many w severe disease.
1 reply 1 retweet 20 likes -
Replying to @lisa_iannattone @zeynep
Reinfection severity data that suggests many can have a more severe course the second time. And this was all pre-delta and pre-omicron. https://secure.jbs.elsevierhealth.com/action/getSharedSiteSession?redirect=https%3A%2F%2Fwww.clinicalmicrobiologyandinfection.com%2Farticle%2FS1198-743X%2821%2900422-5%2Ffulltext&rc=0& … https://www.cdc.gov/mmwr/volumes/70/wr/mm7008a3.htm?s_cid=mm7008a3_w … https://jim.bmj.com/content/69/6/1253 … https://www.medrxiv.org/content/10.1101/2021.10.04.21264540v1 …
1 reply 2 retweets 18 likes -
Replying to @lisa_iannattone
You can have cases here and there more severe—especially with strain changes. But I've seen all those studies. The key issue is the obvious, glaring conditional probability. You cannot only study the re-infections you encounter—obviously sicker than population-wide.
2 replies 0 retweets 6 likes -
Replying to @zeynep @lisa_iannattone
Let me put it this way. There is absolutely no way to explain the epi curve you see in *every* country over time without accepting re-infections and breakthroughs are milder on average. No way. It's the same way droplets/contact only could not explain the epi data. Clear as day.
2 replies 0 retweets 10 likes
Just like why airborne transmission was so obviously true, here, we understand the science, so we get the mechanisms. So here, too, we have population-wide data, solid science, and science and epi data producing a coherent explanation only in one possible way. Can't do better.
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