6 ms·

There are a lot of comments here essentially saying this is not a problem an we are properly reaching herd immunity. I am wondering if these commenters are dis

There are a lot of comments here essentially saying this is not a problem an we are properly reaching herd immunity. I am wondering if these commenters are discounting the possibility of a vaccine? There is a strong possibility that we will have a vaccine before we can safely reach herd immunity.

matz1 6y ago
Not a problem in the sense that, tested positive doesn't mean you are sick, tested positive doesn't mean you are having severe symptom.
nradov 6y ago
The timing and effectiveness of a potential vaccine are still unknown. Hopefully some of the vaccines being tested now will work, but it's quite possible that all will prove to be ineffective or unsafe. So from a public policy standpoint we have to proceed on the assumption that a vaccine isn't going to save us.
tunesmith 6y ago
Natural herd immunity is a non-starter anyway. If we reach herd immunity before a vaccine arrives, the economic damage would be far worse than any shutdown. If the R0 is 5.7, you need 82.5% (4.7/5.7) of the population either immune or quarantined/locked-down. If everyone stops the lockdown, that means 82.5% of the population infected. No matter how much we want to argue down the IFR, that's catastrophic. Semi-related note, I think we haven't properly socialized the basic numbers behind the disease. I hear that Covid-19 is more contagious than first thought, with a "natural" R0 of 5.7. I also hear that it has a doubling time of around three days, originally thought to be more like 5-6. I also hear that the contagion period is 8-10 days. These three numbers do not make sense together. The R0 number needs to be reached during the contagion period. The average contagion period is likely far longer, or, it's way more contagious than 5.7 (which would mean the herd immunity threshold goes higher). Also, if the illness is more contagious than we first thought, it means that the lockdown was even more effective than we first thought. Here's a fun mental exercise for whoever's reading this. Say that you have a bubble of 100 people, and released a disease that infected 50 people and killed all of them; 100% fatality. Then say you discovered that it actually infected all 100 people, but only 50% of them died. Is the disease less dangerous than you first thought?
- wrycoder 6y ago
  The US is at 121K deaths atm. I made an estimate a while back assuming 60% of the population becomes infected and came up with 350K deaths. Bad, but not catastrophic. And I don't think we will get that high.
  - tunesmith 6y ago
    60%/350k assumes an R0 of less than 2.5 (2.5 is to get to 60% herd immunity threshold, and then more infections continue to happen as it dies out), and also an IFR of less than 0.2%. I think those are outside of the range of any recent estimates I've seen. Natural R0 is generally believed to be higher, and IFR is believed to be in the 0.5% - 1% range. I also hope we won't hit 350k, but if we stay below that number, it will be because of a combination of continued lockdowns and finding an effective treatment/vaccine before we reach herd immunity.
    - tripletao 6y ago
      The 1-1/R0 assumes a homogeneous and well-mixed population, and thus overestimates the fraction infected required for herd immunity. For real, people with lots of contacts will get infected and become immune first, with disproportionate benefit. That effect is hard to quantify, but it's near-certainly big, with many papers speculating that herd immunity may occur around 30% recovered: https://www.medrxiv.org/content/10.1101/2020.02.10.20021725v2.full.pdf https://www.medrxiv.org/content/10.1101/2020.02.10.20021725v... This is before considering overshoot, which can occur just as in the homogeneous case (and is a reason to slow the spread as much as reasonable, even if you expect/fear that the end result will be herd immunity from recovered patients). Reported IFRs are now calculated from serostudies testing for IgG. The best studies are on the high end of your 0.5-1%, but there's reason to suspect they're significant overestimates. Sensitivity for the blood tests was established from cases severe enough to seek medical help, and may be much lower for mild cases. There's also evidence of mucosal immunity in patients who test negative for IgG, and recently of T cell response in such patients too: https://www.medrxiv.org/content/10.1101/2020.06.21.20132449v1.full.pdf https://www.medrxiv.org/content/10.1101/2020.06.21.20132449v... And the number of coronavirus deaths is greater than the actual number of excess deaths, since they're disproportionately elderly. All these second-order effects are uncertain, and difficult to incorporate into a final number; but they're real, and to ignore them completely risks a gross overestimate. Maybe people know that, and think of the overestimate as "conservative"; but considering the tremendous costs of both the coronavirus itself and society's response, I strongly disagree. Finally, since you said "lockdowns"--if you credit lockdowns (which are always vaguely defined; but government-imposed restrictions on movement and assembly, broadly) with all of benefit to the USA, how do you explain Japan? They're sitting at 8 deaths per million, they never significantly locked down, and their contact tracers are missing ~80% of cases. Maybe it's the masks? Even in California, use is waning. No one seems to have the political appetite to enforce the order coercively; NYC just stopped enforcing theirs entirely after an incident. Maybe it's the contact tracing anyways, since missing 80% of cases might be fine if you catch the 20% who are super-spreaders (which you will disproportionately, since each person they infect is a chance to find them tracing back)? I could imagine big public campaigns to explain the importance of cooperating with contact tracers, or websites to help people anonymously advise their contacts (which have been tried for STDs, which have at least as much stigma). But I've seen almost nothing. To be clear, I agree that restrictions on movement and assembly were and are a good idea in some cases, and New York and Lombardy surely wish they'd locked down earlier. I just don't like seeing them discussed as if they're responsible for all the difference between our current situation and a first-order model that we know is significantly wrong.

matz1 6y ago

Not a problem in the sense that, tested positive doesn't mean you are sick, tested positive doesn't mean you are having severe symptom.

nradov 6y ago

The timing and effectiveness of a potential vaccine are still unknown. Hopefully some of the vaccines being tested now will work, but it's quite possible that all will prove to be ineffective or unsafe. So from a public policy standpoint we have to proceed on the assumption that a vaccine isn't going to save us.

tunesmith 6y ago

Natural herd immunity is a non-starter anyway. If we reach herd immunity before a vaccine arrives, the economic damage would be far worse than any shutdown. If the R0 is 5.7, you need 82.5% (4.7/5.7) of the population either immune or quarantined/locked-down. If everyone stops the lockdown, that means 82.5% of the population infected. No matter how much we want to argue down the IFR, that's catastrophic. Semi-related note, I think we haven't properly socialized the basic numbers behind the disease. I hear that Covid-19 is more contagious than first thought, with a "natural" R0 of 5.7. I also hear that it has a doubling time of around three days, originally thought to be more like 5-6. I also hear that the contagion period is 8-10 days. These three numbers do not make sense together. The R0 number needs to be reached during the contagion period. The average contagion period is likely far longer, or, it's way more contagious than 5.7 (which would mean the herd immunity threshold goes higher). Also, if the illness is more contagious than we first thought, it means that the lockdown was even more effective than we first thought. Here's a fun mental exercise for whoever's reading this. Say that you have a bubble of 100 people, and released a disease that infected 50 people and killed all of them; 100% fatality. Then say you discovered that it actually infected all 100 people, but only 50% of them died. Is the disease less dangerous than you first thought?

wrycoder 6y ago
The US is at 121K deaths atm. I made an estimate a while back assuming 60% of the population becomes infected and came up with 350K deaths. Bad, but not catastrophic. And I don't think we will get that high.
- tunesmith 6y ago
  60%/350k assumes an R0 of less than 2.5 (2.5 is to get to 60% herd immunity threshold, and then more infections continue to happen as it dies out), and also an IFR of less than 0.2%. I think those are outside of the range of any recent estimates I've seen. Natural R0 is generally believed to be higher, and IFR is believed to be in the 0.5% - 1% range. I also hope we won't hit 350k, but if we stay below that number, it will be because of a combination of continued lockdowns and finding an effective treatment/vaccine before we reach herd immunity.
  - tripletao 6y ago
    The 1-1/R0 assumes a homogeneous and well-mixed population, and thus overestimates the fraction infected required for herd immunity. For real, people with lots of contacts will get infected and become immune first, with disproportionate benefit. That effect is hard to quantify, but it's near-certainly big, with many papers speculating that herd immunity may occur around 30% recovered: https://www.medrxiv.org/content/10.1101/2020.02.10.20021725v2.full.pdf https://www.medrxiv.org/content/10.1101/2020.02.10.20021725v... This is before considering overshoot, which can occur just as in the homogeneous case (and is a reason to slow the spread as much as reasonable, even if you expect/fear that the end result will be herd immunity from recovered patients). Reported IFRs are now calculated from serostudies testing for IgG. The best studies are on the high end of your 0.5-1%, but there's reason to suspect they're significant overestimates. Sensitivity for the blood tests was established from cases severe enough to seek medical help, and may be much lower for mild cases. There's also evidence of mucosal immunity in patients who test negative for IgG, and recently of T cell response in such patients too: https://www.medrxiv.org/content/10.1101/2020.06.21.20132449v1.full.pdf https://www.medrxiv.org/content/10.1101/2020.06.21.20132449v... And the number of coronavirus deaths is greater than the actual number of excess deaths, since they're disproportionately elderly. All these second-order effects are uncertain, and difficult to incorporate into a final number; but they're real, and to ignore them completely risks a gross overestimate. Maybe people know that, and think of the overestimate as "conservative"; but considering the tremendous costs of both the coronavirus itself and society's response, I strongly disagree. Finally, since you said "lockdowns"--if you credit lockdowns (which are always vaguely defined; but government-imposed restrictions on movement and assembly, broadly) with all of benefit to the USA, how do you explain Japan? They're sitting at 8 deaths per million, they never significantly locked down, and their contact tracers are missing ~80% of cases. Maybe it's the masks? Even in California, use is waning. No one seems to have the political appetite to enforce the order coercively; NYC just stopped enforcing theirs entirely after an incident. Maybe it's the contact tracing anyways, since missing 80% of cases might be fine if you catch the 20% who are super-spreaders (which you will disproportionately, since each person they infect is a chance to find them tracing back)? I could imagine big public campaigns to explain the importance of cooperating with contact tracers, or websites to help people anonymously advise their contacts (which have been tried for STDs, which have at least as much stigma). But I've seen almost nothing. To be clear, I agree that restrictions on movement and assembly were and are a good idea in some cases, and New York and Lombardy surely wish they'd locked down earlier. I just don't like seeing them discussed as if they're responsible for all the difference between our current situation and a first-order model that we know is significantly wrong.