We have the first study (still un-peer-reviewed) that advances an evidence-based hypothesis for why Omicron COVID may actually produce milder disease. I want to emphasize this is a single study, which has not undergone peer review. The gist is that Omicron was much faster at taking hold in the air passage leading to the lungs but much less efficient in replicating in lung tissue. The surmise is that this makes it much better at jumping from host to host – which is demonstrated by rate of spread in multiple countries – but much less efficient at creating illness once it gets into the lungs.
Muge Cevik, a virologist at the University of St. Andrews (who is one of the people on my COVID expert list), notes another study which seems to support these findings.
It is important to note that rate of replication in the lungs is not the only driver of disease severity. So it is best to see this as a possible and partial explanation of why Omicron may be much more transmissible while also producing a more mild version of the illness.
As we’ve discussed, there is already evidence that Omicron is producing, on average, milder disease than earlier variants. But based on available evidence the best explanation for this is that it does a better job of infecting people with existing immunity. So the “milder” disease isn’t really a sign Omicron is milder, only that it infects people whose immune systems are better able to fight it. That said, that doesn’t rule out the possibility that Omicron also produces milder disease in itself. This is the first study at least that I’ve seen that suggests that may be the case and provides a clinical description of why that may be the case.
A couple other points. Remember: get that booster. I continue to read up on the progress of Omicron in countries where the Omicron wave is further advanced. South Africa and then a group of countries in Western Europe. The rate of growth is simply explosive. There’s no other way to put it. The CDC released some data yesterday suggesting that Omicron currently accounts for just under 3% of US cases. So the surge that is already underway here is mostly not Omicron. But we should expect a very, very large wave of infections in the coming weeks, in part because of Omicron but also because of what seems to be a standard COVID winter surge. The pace and scope of the surge looks likely to be something like the original one in the Spring of 2020.
That doesn’t mean it will be as bad. The vast majority of the people in the United States now have some immune experience with COVID, either through infection or vaccination. As a population we’re much more prepared. But even with a potentially milder strain and vaccine protection that many people getting sick will land a lot of people in the hospital and end a lot of lives. Just yesterday, in advance of this surge, 1,732 people in the US died of COVID.