Note:
My last, and best, COVID-19 science article
on my climate science blog is here:
https://elonionbloggle.blogspot.com/2020/08/this-is-my-last-and-best-science.html
"Don't let it (COVID -19)
dominate your life "
President Trump,
October 5, 2020
INTRODUCTION:
I promised no more Coronavirus science articles on my popular climate science blog a while ago, and I've kept my promise. But I'm fed up with the misinformation about Sweden and "herd immunity. A lot of it comes from Washington, D.C., or is repeated by people who work there and get high salaries. ... And this is "a blog about lying and lawbreaking in "Warshington", DC" !
The COVID-19 pandemic is not over. So there are no COVID-19 experts yet, including me. There ARE many self proclaimed COVID-19 "experts", claiming Sweden did everything right, and now they have "herd immunity".
I doubt if they know what herd immunity means. Some claim COVID-19 was no worse than a typical seasonal flu. They are clueless. The effect of the partial lockdowns ALONE, both economic effects and health related effects, were worse than any pandemic since the 1918 flu ... that killed my mother's twenty-something mother (my grandmother) when my mother was only two years old. Add the direct health effects, and this is a horrible pandemic ... still in progress.
Lots of nations had better results than Sweden, Including neighboring Norway. I suspect nations' results were significantly influenced by how many Chinese people flew there in early 2020. That probably helped Taiwan a lot. The next factor is how well nations and states protected their nursing homes. Not well in Sweden. And then there is good or bad luck, aka random variations. ... My only advice is to take 2,000 to 3,000 IU of Vitamin D every day, for each 100 pounds of your weight, and get at least 15 minutes of sunlight too.
SUMMARY:
Sweden had a moderate death rate, lots of deaths in nursing homes and Real GDP fell over 7% in the first half of 2020. High schools and colleges were locked down. Large events were not allowed. People were asked to voluntarily social distance, and they did, causing the business decline. Social distancing might have been easier because roughly half of Swedish households are a single person. Masks were not required, but would have been useful.
There is no indication yet of much of a Swedish COVID-19 "second wave", so some people are declaring Sweden has "herd immunity". That's not likely to be true. Herd immunity is not required to avoid a second wave.
There's no logical reason to cherry pick Sweden, and completely ignore neighboring Norway and Denmark, with much better COVID results. Or Taiwan. Or all of Asia, except China. People keep talking about herd immunity in Sweden, yet have no idea what herd immunity means.
Herd immunity does NOT mean COVID-19 fatalities stop. Herd immunity is just where the reproductive rate Rt would drop below 1.0 in the absence of containment measures. Herd immunity is NOT enough to stop a disease entirely, but it’s enough to stop it from GROWING. There’s nothing that requires any nation to get to herd immunity.
To contain the spread of the virus, we don’t need herd immunity. We do need to reduce the probability of contact with an infected person who will transmit the disease, using face masks in shared indoor public spaces, along with increased person-to-person distances, shorter person- to-person interactions, hand washing and disinfecting common touch points. This is 50+ year old advice that applies to influenza, in general.
Especially avoid “super spreading” events where one infected person can come into contact with lots of uninfected people. That includes crowded bars with loud music and people "shouting" at one another.
Quickly isolate new cases to prevent transmission to additional people, and trace their recent contacts to warn those people that they need to be tested. Isolating the sick people -- what a novel idea! And isolate the people in nursing homes. They may be nearing "the end" anyway, but many have contributed a lot to society in their lives, and they deserve to live just as much as younger people do.
We need a high level of containment of new outbreaks, not stringent containment of the whole U.S. population. And strong, rapid result testing and contact-tracing measures, when new infections do break out. Masks are somewhat helpful, but far from "the answer".
DETAILS:
SARS-CoV-2 is not an influenza virus. COVID-19 is not the common cold. This virus alters the immune system, reduces the defenses of airway cells, and CAN trigger an inflammatory cascade that can lead to severe acute respiratory distress, degradation of blood vessel linings, tissue damage, and death.
I'll assume all people are susceptible. “R0” is the “basic reproductive rate.” It’s determined by the infectivity of the disease (p), the average number of contacts (N), and the duration of infectivity (D).
As more people have had the disease, and recovered, or died, the pool of susceptible people declines, so the rate of infection will slow.
If the whole population is vulnerable, let's assume each infected person transmits the disease to an average of R0 other people (using a 2.6 R0, for this example). That's a reasonable estimate of the R0 of COVID-19.
If we reduce the pool of susceptible people to 1/R0 of the population (38% for this example), then each newly infected person will infect not R0 people, but R0 x 1/R0 = one additional person. At that point, 1–1/R0 of the population (62% in this example) would already have been infected, and would have antibodies, and that 62% would be called “herd immunity.”
Herd immunity for COVID-19 in the U.S. would be a nightmare. 62 percent of 350 million people , or 217 million Americans, would have to get COVID and develop long lasting antibodies that would protect them. If I assume 20 million Americans have already been infected (causing 1 death out of of 100 infected, or 200,000 deaths) and they already have long lasting antibodies, then 197 million more Americans would have to be infected, and develop long lasting antibodies too, to reach herd immunity.
The initial death rate has declined a lot as the most vulnerable people in nursing homes died, and doctors learned how to prevent deaths since March and April 2020. I'll assume only 1 of 1,000 new infections results in death now (an optimistic, but realistic estimate). That would mean 197,000 more Americans would die (1 of 1,000, of 197 million Americans) to reach a reasonable estimate (62%) of herd immunity. Add perhaps 118 million more Americans suffering normal flu symptoms, or serious flu symptoms, but they would survive (60% of 197 million). And 79 million more Americans would suffer with mild flu symptoms, or no symptoms (40% of 197 million).
You slow down an epidemic by reducing
the probability that contact with an infected person will transmit the disease:
-- Reduce the number of contacts and social interactions, particularly involving ‘super-spreading’ events;
-- Reduce the duration of infectivity, by quickly isolating new cases and tracing their contacts.
About 40% of people with COVID-19 do not exhibit any symptoms (asymptomatic), or have mild symptoms, yet have similar viral loads and infectivity. Roughly half of asymptomatic adult cases still show some level of inflammatory lung damage, consistent with injury to alveolar cells (the “air sacs” of the lung). That may be why some people say “I feel fine,” but when you check their oxygen saturation, it’s down to 85% to 95%.
Cases that are asymptomatic at the time of testing, and then go on to produce symptoms later (“pre-symptomatic”), have a longer communicable period (~14 days). Viral load is reported to be similar across groups. The transmission of the live SARS-CoV-2 virus hasn’t been reported beyond 10 days after symptoms emerge.
Both symptomatic and asymptomatic cases of COVID-19 generate mucosal (IgA) antibodies in the early stage of inflection, with virus-specialized antibodies (IgG) appearing later, reportedly making tests that include IgA more timely and reliable. Asymptomatic cases produce lower levels of large, acute-stage, early-response antibodies (IgM), as well as fewer inflammatory markers like IL-6 and CRP.
Circulating antibody levels should gradually decline after an infection. That doesn’t mean COVID-19 immunity has been lost. It just means that the body has “memory” B-cells, and doesn’t need to crank out antibodies when they’re not needed.
