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> Doesn't the fact that it's outcompeting Delta imply that there is some cross immunity? Not really. If Delta's Rt is greatly reduced because lots of people h

by mlyle 5y ago

> Doesn't the fact that it's outcompeting Delta imply that there is some cross immunity? Not really. If Delta's Rt is greatly reduced because lots of people have immunity, Omicron can show up with a much higher Rt and grow in case numbers. It doesn't need to further reduce Delta's Rt to "win". I.e. even if R0 among those naive to the variants is similar, once you have 2/3rds of people who can't get Delta because of vaccination or prior infection and that can get Omicron, ... Omicron is going to win. And it looks like Omicron may be more contagious than Delta at baseline, so it's even quicker.

throwaway55421 5y ago
Yes, sorry, that's not what I thought "outcompeting" meant in the epidemiological sense. I thought it implied that one variant grows to the detriment of the other. Otherwise, we could say something like "COVID outcompetes the flu". I don't think we have the data on Omicron vs Delta yet as you say.
- mlyle 5y ago
  > Yes, sorry, that's not what I thought "outcompeting" meant in the epidemiological sense. I thought it implied that one variant grows to the detriment of the other. I mean, it does, but ... we don't really know that Omicron is outcompeting Delta in that sense. We know that Omicron case counts are growing, relative to Delta, but we don't know how well Omicron prevents later infection by Delta, etc. You asked "Wouldn't the fact that it's outcompeting Delta imply that there is some cross immunity?" The only fact that we have right now is that Omicron is growing quicker than Delta, not that Omicron is somehow suppressing Delta with cross-immunity. > Otherwise, we could say something like "COVID outcompetes the flu". Well--- COVID causing everyone to be careful, combined with influenza's lower Rt due to not being novel, really put a dent in influenza. So even then, without cross-immunity, you can have growth in one suppress growth in the other.
  - throwaway55421 5y ago
    Gotcha. yeah I agree on all of that.

by mlyle 5y ago

throwaway55421 5y ago

Yes, sorry, that's not what I thought "outcompeting" meant in the epidemiological sense. I thought it implied that one variant grows to the detriment of the other. Otherwise, we could say something like "COVID outcompetes the flu". I don't think we have the data on Omicron vs Delta yet as you say.

mlyle 5y ago
> Yes, sorry, that's not what I thought "outcompeting" meant in the epidemiological sense. I thought it implied that one variant grows to the detriment of the other. I mean, it does, but ... we don't really know that Omicron is outcompeting Delta in that sense. We know that Omicron case counts are growing, relative to Delta, but we don't know how well Omicron prevents later infection by Delta, etc. You asked "Wouldn't the fact that it's outcompeting Delta imply that there is some cross immunity?" The only fact that we have right now is that Omicron is growing quicker than Delta, not that Omicron is somehow suppressing Delta with cross-immunity. > Otherwise, we could say something like "COVID outcompetes the flu". Well--- COVID causing everyone to be careful, combined with influenza's lower Rt due to not being novel, really put a dent in influenza. So even then, without cross-immunity, you can have growth in one suppress growth in the other.
- throwaway55421 5y ago
  Gotcha. yeah I agree on all of that.