3 ms·

> Another thing to consider is also that if you vaccinate people to reach herd immunity, you effectively pick people at random and give them immunity. But if a

> Another thing to consider is also that if you vaccinate people to reach herd immunity, you effectively pick people at random and give them immunity. But if a virus spreads naturally through a population, it won't pick people at random, it will pick the best spreaders first, and when those have either died or recovered, it will pick the next best spreaders and so on. The remaining population will successively contain worse and worse candidates for natural spread, which means that the threshold for herd immunity is much lower. Yes, this is a great point that often gets missed. This is the principle of vector exhaustion: by definition, those more likely to get infected will get infected first. Insofar as someone more likely to get infected is also more likely to infect others, that means that we see a non-linearity to herd immunity. Getting that first group of highly infectious people immune works wonders.

CWuestefeld 6y ago
I don't think the grandparent post is correct. It's not that those who spread best are infected first. It's the ones that are most easily infected (because of their particular biology, lifestyle, etc.) who are first infected. I believe (but honestly am not certain) that one's susceptibility to infection is independent of one's ability to spread more effectively.
- henrikschroder 6y ago
  Sure, I'm not saying that there is perfect overlap between the most susceptible and the most infecting individuals. But people who travel around a lot, meet a lot of different people, are simply more likely to encounter an infected person and get infected, and in turn are more likely to unknowingly infect everyone else they meet. The same mechanisms that make someone a "super spreader" is also what makes them more likely to get infected, and to get infected early in the pandemic. We know that for example medical personnel got infected in way higher numbers than the general population, for obvious reasons. But they're now also more immune than the general population, for the same obvious reasons. And as a result, intra-hospital spread decreases. Yes, it's two independent measures, but with very high correlation.
  - CWuestefeld 6y ago
    Hmmm. That's a pretty good argument. The biological component is probably completely separate, but the lifestyle component, the opportunity part, overlaps significantly.
- __blockcipher__ 6y ago
  I am also highly uncertain of this. Briefly though, elderly people are more susceptible to actual infection, and I would think would be more likely to express symptoms / have higher viral load. So it depends if the marginal likelihood of more symptoms = self-isolating sooner is counterbalanced by more symptoms = spread more easily for a given encounter. Anyway, ignoring the spreading part, the susceptibility alone does explain it to an extent, as you implied: > It's the ones that are most easily infected (because of their particular biology, lifestyle, etc.) who are first infected.

CWuestefeld 6y ago

I don't think the grandparent post is correct. It's not that those who spread best are infected first. It's the ones that are most easily infected (because of their particular biology, lifestyle, etc.) who are first infected. I believe (but honestly am not certain) that one's susceptibility to infection is independent of one's ability to spread more effectively.

henrikschroder 6y ago
Sure, I'm not saying that there is perfect overlap between the most susceptible and the most infecting individuals. But people who travel around a lot, meet a lot of different people, are simply more likely to encounter an infected person and get infected, and in turn are more likely to unknowingly infect everyone else they meet. The same mechanisms that make someone a "super spreader" is also what makes them more likely to get infected, and to get infected early in the pandemic. We know that for example medical personnel got infected in way higher numbers than the general population, for obvious reasons. But they're now also more immune than the general population, for the same obvious reasons. And as a result, intra-hospital spread decreases. Yes, it's two independent measures, but with very high correlation.
- CWuestefeld 6y ago
  Hmmm. That's a pretty good argument. The biological component is probably completely separate, but the lifestyle component, the opportunity part, overlaps significantly.
__blockcipher__ 6y ago
I am also highly uncertain of this. Briefly though, elderly people are more susceptible to actual infection, and I would think would be more likely to express symptoms / have higher viral load. So it depends if the marginal likelihood of more symptoms = self-isolating sooner is counterbalanced by more symptoms = spread more easily for a given encounter. Anyway, ignoring the spreading part, the susceptibility alone does explain it to an extent, as you implied: > It's the ones that are most easily infected (because of their particular biology, lifestyle, etc.) who are first infected.