Pathology
This article suggests that the reason that COVID-19 hits old people so much harder than young people is that old people have more antibodies to important pieces of their own innate immune system, particularly interferons. (In other words, they attack critical pieces of their own immune system.) They found that the proportion of people who had autoantibodies to type I interferons was
- 0.18% in people 18-69 y/o;
- 1.1% in people 70-80 y/o;
- 3.4% in people over 80 y/o.
The article wondered about why old people had more interferon autoantibodies, but didn’t speculate. I have zero expertise in the subject, so I can speculate wildly that it’s a feedback loop: if you get a little bit of damage to your immune system, it has to work harder next time, so makes a wider variety of antibodies, which means there is a greater chance that one of the antibodies will be a rogue and eat parts of your immune system. Which makes it harder to clear an infection, so you create more antibodies, ad nauseum.
The article mentions that COVID-19 kills 10% of people over 80 but less than 0.001% of individuals below 18 years old. I hadn’t ever seen it put like that.
Long COVID
This preprint from the UK found that people who had two doses before a COVID-19 infection were 40% less likely to get Long COVID as people who had no doses before infection. (This was pre-Omicron; I don’t think I have seen any studies yet on Omicron Long COVID, just because it hasn’t been long enough after the Omicron wave started.)
Recommended Reading
This article is a nice summary of what is different and scary about Omicron. If you are a frequent/detailed reader of this blog, nothing will be new, but it’s a nice recapitulation.