Tamsin Brooks on Don't Worry About the Vase

[Tamsin Brooks]

I love your pieces. This is some thoughtful writing. But I can't agree with you when it comes to the idea that Omicron will be intrinsically "milder" than Delta. I'm afraid that at this point, based on the evidence we have, this may be wishful thinking. The reason is that so far, Omicron is behaving exactly the way it would if it both the morbidity and mortality rates *and* the population severely affected were basically the same as Delta, no better, no worse. Take this quote after the analysis of hospitalizations, for instance: "The thread that was in gives some caveats on the hospital numbers, they get revised upwards later and lag cases, but still. " They were revised upwards later, and they do lag cases. But that doesn't cover the issue with this. Because right after this, you reprint a tweet stating that the cases are trending very young, just as South Africa's population is very young (average age 26.) If Omicron behaves like Delta in terms of mortality and morbidity, we would 100% expect to see milder cases in the young... and we're seeing milder cases in the young. If Omicron acts like Delta in terms of vaccines providing protection against severe outcomes, then we'd see exactly what we are seeing, which is vaccines providing protection against severe outcomes. Most cases of Delta are mild; most cases of Omicron are mild. Many countries have unhooked the number of cases from the number of deaths, like the UK; there's no reason to think it will be different with the new variant. Omicron is doing nothing to date that is consistent with the theory that it is intrinsically milder than Delta, only that under specific circumstances, it is *as* mild as Delta-- but only under those circumstances. There is nothing indicating that the virus itself has become "milder."

I understand feeling hopeful about it (and I think it's significant that "hopeful" is the word you use.) But a number of factors are going to have to change before it's at all possible to say that the virus itself has become any milder, and they have not changed yet. The vast majority of all the confirmed cases with Omicron being identified and discussed are in one of two groups: the fully vaccinated, or the very young. In those populations, Omicron is behaving just like Delta did. The cases were mild then; the cases are mild now. Once this new variant really gets its teeth into a population like the US, with significant numbers of people who are both unvaccinated and in the risk groups that would have had serious problems with Delta, we're going to see if this continues to be the case or not. We will need to compare the young and/or vaccinated cases vs. young and/or vaccinated hospitalizations and deaths *and then* older/lots of pre-existing conditions/unvaccinated cases vs. older/lots of pre-existing conditions/unvaccinated cases hospitalizations and deaths. They can't all be lumped together, or it will make no sense at all. But based on the current facts as they stand, the facts that we actually have, I think that it just can't be claimed that the virus has itself become any milder than Delta.

[Zvi Mowshowitz]

I agree that what we're seeing would be broadly compatible with Omicron=Delta in terms of what happens if a given person catches it. I also think it's broadly consistent with it being milder, and it's unclear what answer you would get if you controlled for all that stuff properly (and thus, what the ultimate answer will be), and I would be very unsurprised by either outcome. I don't think we get the luxury of 'can't be claimed' (or the similar 'no evidence') here, and I notice that the news does seem better on this front than I expected after accounting for all these factors as best I can.

And of course, I stand very ready to change my tune in either direction very quickly when new data comes in.

[Tamsin Brooks]

Thanks for the reply! I really do love your posts. I just feel that right now, we cannot compare apples to apples with the young patients who are being hospitalized in South Africa at the moment vs. the much older population in the US. Time will tell, and in a few months, the picture will be much clearer.