Bikers descend on Sturgis rally with few signs of pandemic

Discussion in 'Coronavirus (COVID-19) News' started by CenterField, Aug 8, 2020.

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  1. Lesh

    Lesh Banned

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    My point has always been that if you are going to surrender to the virus and just let people get exposed to it...you better have some solid numbers in your favor.

    And we do NOT have that.
     
  2. CenterField

    CenterField Well-Known Member Past Donor

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    The issue is, there is no fixed number. I though I had explained it (and the authors above, did). Look at what the authors said, it's variable "rather than as an exact value or even a best estimate." It varies according to the population, the season, the behavior of the population (in terms of epidemiological control measures they adopt), the susceptibility of the population (which varies with race, gender, blood type, level of vitamin D, previous encounters with common cold-causing coronaviruses, etc.), the density of he population, and so on and so forth.

    I agree with you in the fact that I do not believe that Sweden or Stockholm or NY or the US have achieved herd immunity yet. I do disagree with 577's estimate on this (respectfully; its'not like he doesn't have some strong points). But there is no fixed number. It could be as low as 33% for certain populations and geographic areas, or as high as 92% for other populations.

    In the slums of São Paulo, Brazil, a population was found for which the R0 number was 12 (given crowded quarters, no masks, poverty with no access to hygiene items like sinks and showers, no ventilation, predominantly black people), maybe the highest ever recorded for the SARS-CoV-2. For that pocket of population with a R0 of 12 - almost measles numbers - the HIT would have to be 91.6%. Say, you have on the other hand a population of people who take extremely good epidemiological control measures, they live in single family homes, they are white (Hispanics and blacks are more susceptible), all their kids go to the same school and the school had a huge outbreak of a coronavirus-caused common cold and everybody got it, and they all have high levels of vitamin D given that most of them go to a primary care office there in the neighborhood where the doctor is adamant about Vit D supplements, it's high summer and people are not hanging out indoors, so that for that population the R0 number is 1.5, the HIT for them will be 33.3%.

    There is a theoretical "basic" R0 number, and an Re number which is called the "effective" reproduction number, in real life, according to various factors. The latter is more conducive of calculating the HIT for a given subset of the population such as a borough, a county, a city...
     
  3. CenterField

    CenterField Well-Known Member Past Donor

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    R0 = basic reproduction number, more linked to the virus' basic infectiousness
    Re = effective reproduction number, more linked to the real-life ability of the virus to get transmitted, according to precautions used by susceptible subjects, and the degree of susceptibility in the population.
    The latter is smaller than the former if people take precautions.
    The British Medical Journal has put together a simple, lay-person accessible explanation, here:
    https://www.bmj.com/content/369/bmj.m1891
    And I love your demo!
     
  4. ronv

    ronv Well-Known Member

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    I have been looking for a way to calculate Re that doesn't take a math degree. Have you seen one?
    I'm not so interested in mitigation but with the number of people already infected.
     
  5. Lesh

    Lesh Banned

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    Then you sure as **** better not be basing policy on it.

    And if you do...use the "simplified" numbers that the Mayo Clinic uses
     
  6. CenterField

    CenterField Well-Known Member Past Donor

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  7. CenterField

    CenterField Well-Known Member Past Donor

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    It's not entirely unreasonable to use a "simplified" number representing the average of several Re's for a country, so some places will have a higher HIT, others will have a smaller one, all things considered we'll get to a sort of national average. I suspect, just gut-feeling wise, that the average for the United States sits somewhere around 50% to 60%. I think that the top range of 70% of the Mayo Clinic is probably too high; it seemed this way in the early days of the pandemic but it seems like there is some slow down already especially in certain areas that have passed peak, and there's been the notion of more sub-sets of the population that are less susceptible, some notion of cross-immunity with common cold coronaviruses, so all things considered I think that we don't need to get as high as 70% of the entire population infected, to see the Re drop below 1.0 (when this happens, the outbreak starts to dwindle).

    Let's hope it's around 50% because if we have a highly efficacious vaccine (and three of the vaccines, the Sputinik V, the CoronaVac, and the Novavax, all three supposedly yielded immunogenicity above 97% (the CoronaVac kept 98% even for the elderly; seems like the most efficacious one, so far). If the HIT national average is around 50%, less than half of the population would need to accept a 98% efficacious vaccine for us to achieve herd immunity (less than half because there's the people who already have natural immunity, from having survived the disease). About 45% of Americans accept the flu shot every hear. Presumably we'd achieve at least that much with the Covid-19 shot. Say, after the end of phase 3 we get a vaccine that is 95% efficacious and 45% of us take it. That would result in 42.75% of the population being immune via the vaccine. We'd need only 7.25% of the population with natural immunity, to get to 50%. If we are missing two out of three infections, we're at about 6% already. If we are missing 4 out of 5 we're already there.

    Unfortunately these high-performing vaccines are not the ones that are likely to win the domestic race. These would be the Moderna one and the Pfizer one (the AstraZeneca one seems out of commission, now), and these are both mRNA vaccines, which are unproven and might be much less efficacious than the CoronaVac, which is Chinese therefore not likely to get to us anytime soon.

    Our own Novavax, though, looks very promising. It's still in phase 2 but has yielded 100% efficacy in phase 1. It is a protein subunit vaccine, a platform much more established than the mRNA platform.

    After the Oxford/AstraZeneca setback I'm placing my hope on Novavax.
     
    Last edited: Sep 11, 2020

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