5 ms·

> and we are no near achieving any herd immunity. I wouldn't be so sure about that, actually. Sweden's response has been widely reported on, and even more wid

> and we are no near achieving any herd immunity. I wouldn't be so sure about that, actually. Sweden's response has been widely reported on, and even more widely mis-reported on. Sweden chose the least amount of restrictions in the EU, and mobility analysis shows that although the Swedish people changed behaviour drastically, they did it the least of the EU countries. People were doing the most distancing in late March, same as everywhere else, and have been slowly easing up ever since. And yet, the death rate has been going down steadily in Sweden since mid-April. Testing has been too low for a long time, but is finally up at reasonable numbers. And yet, the positive test rate has been cratering the past few weeks. The Swedish public health agency have done a bunch of random samplings of antibodies to measure the immunity rate, and it always came back at much lower levels than expected. The peanut gallery was quick to crow that Sweden's "herd immunity" strategy was a complete failure, zombie apocalypse etc, but the reason people were surprised that the antibody levels were so low is because it didn't match the actual spread. Something is pushing the death rate and case levels down in Sweden, it clearly isn't lockdown or distancing measures, and it clearly isn't sars-cov-2-specific antibodies. There are reports out now that a lot of people seem to have immunity or resistance through T-cell response, presumably as a result of earlier coronavirus exposure. 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. And all of these things together suggest that herd immunity is easier to achieve than we initially thought, and that regions that have been heavy hit, but that now see very little death and cases, might be very close to it.

__blockcipher__ 6y ago
> 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.

__blockcipher__ 6y ago

> 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.