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I’m convinced that seroprevalence studies greatly underestimate the true level of immunity of a given population to COVID.
Take Sweden: point is not whether they did the right thing. I think they didn’t & lost a lots of lives. The point is given the low seroprevalence & continued lack of lockdown etc how did their COVID rates plummet? Is their seroprevalence capturing the true % of immune population
By immune I don’t mean immune from not having COVID PCR positive if you go checking for it. But immune from having symptomatic COVID. @Rfonsi1
Just a bit of background. I’ve done a few threads on this topic. But until we have more proof, everyone should consider themselves susceptible and act accordingly. Don’t relax. Masks. Social distance.
In March, I first thought not all people can be susceptible based on Wuhan. https://twitter.com/vincentrk/status/1244347036293627910
In March, I first thought not all people can be susceptible based on Wuhan. https://twitter.com/vincentrk/status/1244347036293627910
Then Lombardy and NY made it more possible that a subset of the population may may not be susceptible (?due to cross immunity or T cell immune response) because I didn’t think it was possible to have steep sustained drops with just 10-20% seroprevalence. https://twitter.com/vincentrk/status/1274792133929639936
Then we had the fascinating Antarctica cruise ship story. How can we have 10 rooms, 2 people in each for 20-30 days together and one has COVID and one doesn’t? https://twitter.com/vincentrk/status/1275838416236580867
Then we had a bunch of studies that showed people can be sero negative but have robust T cell responses specific to SARS CoV-2; & people who had T cells reactive to SARS-CoV-2 b4 we had the COVID pandemic! Are these protective? Don’t know. But they can explain some of the above. https://twitter.com/vincentrk/status/1278017849781563394
I’m linking this because there’s great discussion in a subtweet than can get lost. @jhuber 
https://twitter.com/jhuber/status/1284253357524135936
https://twitter.com/jhuber/status/1284253357524135936
This is good supporting data.
If you have symptoms and PCR positive, then we know seroconversion occurs >90% of the time.
If you screen and detect PCR positivity, only about 50% seroconvert. Explains some of the things in this thread. Thanks @rfsquared https://twitter.com/rfsquared/status/1284591153845809152
If you have symptoms and PCR positive, then we know seroconversion occurs >90% of the time.
If you screen and detect PCR positivity, only about 50% seroconvert. Explains some of the things in this thread. Thanks @rfsquared https://twitter.com/rfsquared/status/1284591153845809152
One more study @NatureMedicine showing asymptomatic COVID people can become seronegative quickly. Authors warned that they may not be immune. But we have to keep in mind that they very well could be immune & wont be captured in seroprevalence studies. https://www.nature.com/articles/s41591-020-0965-6
In this study 40% of asymptomatic people became seronegative. And 13% or symptomatic. Depending on when seroprevalence studies are done relative to when they were infected, these people will not be called seropositive.
People have asked me if I’m concerned that antibody levels appear to decrease after COVID infection, and what it means for vaccines. I’ve said repeatedly I’m not. Antibody levels may go down even to the point of not being detectable. But the memory cells will be there https://twitter.com/vincentrk/status/1285022130556538880
https://twitter.com/vincentrk/status/1285022130556538880
