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Wed Apr 8, 2020, 03:08 AM

California Herd Immunity?

I know a lot of people who had the worst “flu” of their lives this past late fall and early winter. And many of the Asian kids wearing masks to school.

https://www.ksbw.com/article/new-study-investigates-californias-possible-herd-immunity-to-covid-19/32073873

19 replies, 2414 views

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Arrow 19 replies Author Time Post
Reply California Herd Immunity? (Original post)
Bluesaph Apr 2020 OP
TeamPooka Apr 2020 #1
ProfessorGAC Apr 2020 #8
LizBeth Apr 2020 #2
BigmanPigman Apr 2020 #3
Squinch Apr 2020 #6
a la izquierda Apr 2020 #15
BigmanPigman Apr 2020 #16
a la izquierda Apr 2020 #18
Journeyman Apr 2020 #4
Voltaire2 Apr 2020 #5
Celerity Apr 2020 #9
Voltaire2 Apr 2020 #13
MFM008 Apr 2020 #7
Baclava Apr 2020 #10
nilesobek Apr 2020 #11
Mariana Apr 2020 #12
Proud Liberal Dem Apr 2020 #14
andym Apr 2020 #17
Baclava Apr 2020 #19

Response to Bluesaph (Original post)

Wed Apr 8, 2020, 03:13 AM

1. my spouse was one of those. Got the flu on Dec 18th and was sicker than she had ever been

in 20 years. And was sick for several weeks too.
The cough stayed with her for almost 6 weeks

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Response to TeamPooka (Reply #1)

Wed Apr 8, 2020, 05:11 AM

8. She Was Sick When I Was

Pretty close, anyway. I was feeling better by the 17th, but hit me like a ton of bricks the weekend prior.
Subbed at a school week before, and 3 regular teachers, 12 kids (tiny school) and secretary all got sick with bronchitis or pneumonia, all within 2 weeks.
Thing that make you go, hmmmm!

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Response to Bluesaph (Original post)

Wed Apr 8, 2020, 03:19 AM

2. Oregon too. Different from a cold, not a flu. But, we didn't see bad cases, just mediocre'ish.

There weren't deaths. It took out our front desk first week in January. We get a lot of traffic from Washington thru California and I had conversation with more than one about these symptoms we experienced.

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Response to Bluesaph (Original post)

Wed Apr 8, 2020, 03:50 AM

3. Someone on DU said that she and her co-workers

all had some kind of bad flu in Jan or Feb. I believe she lived in WA or OR though.

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Response to BigmanPigman (Reply #3)

Wed Apr 8, 2020, 04:44 AM

6. I had one in January in NY. The cough lasted about 2 months.

Can't wait till an antibody test is widely available.

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Response to Squinch (Reply #6)

Wed Apr 8, 2020, 10:05 AM

15. Same.

My cough lasted a month and was awful.

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Response to a la izquierda (Reply #15)

Wed Apr 8, 2020, 06:03 PM

16. Is it the kind of cough

where you cough so much that your chest muscles get sore and it hurts to cough? That is what happens to me when ever I get bronchitis or pneumonia.

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Response to BigmanPigman (Reply #16)

Wed Apr 8, 2020, 06:58 PM

18. I've had bronchitis before...

This pain and the cough was really weird. Really weird right feeling in my sternum.

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Response to Bluesaph (Original post)

Wed Apr 8, 2020, 03:56 AM

4. I encountered a number of people in the past 4 or 5 months who were sick for a long time . . .

and as I remember, most said it never became the flu but felt like it at times.

Maybe there's something to this idea.

I never got sick, nor did anyone within my immediate family, but it would be nice to know there's a greater buffer around us, even if I do have to remain socially distanced.

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Response to Bluesaph (Original post)

Wed Apr 8, 2020, 04:41 AM

5. 90% or more required.

So actual herd immunity very unlikely.

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Response to Voltaire2 (Reply #5)

Wed Apr 8, 2020, 06:24 AM

9. nowhere near 90% is needed, someone gave you bad info, it is somewhere between 50 and 66% depending

on the (reproductive ratio) An of 2.5 would mean 60% would need to be exposed. An of 2.0 would mean 50% would be the number. An would mean 66% is needed.


Some estimates

https://www.sciencemediacentre.org/expert-comments-about-herd-immunity/

Prof Willem van Schaik, Professor of Microbiology and Infection, University of Birmingham, said:

“Herd immunity describes the phenomenon that at-risk individuals are protected from infection because they are surrounded by immune individuals. The spread of the virus is thus minimised. Currently, we talk mostly about herd immunity in the context of vaccines. If a sufficiently high number of individuals in a population are vaccinated, they will provide herd immunity to the small number of people that are not vaccinated (e.g. for medical or religious reasons). We have recently seen cases of measles outbreaks where herd immunity was not sufficiently high because children were not vaccinated out of completely unfounded fears against vaccination.

“Herd immunity exists for flu. If large proportions of the population would get a flu vaccine that could protect non-immunised individuals. The problem with flu is that it is difficult to know which strains of flu (think of strains as variations on a theme: it is flu but just a little bit different) will be causing infections at any given point in time and so that is why the flu vaccine is not always 100% effective. The major problem with coronavirus is that this is a novel virus that has never spread before, which means that everyone is at risk for infection. Herd immunity can only be reached by widespread vaccination (but there is currently no vaccine, and it may take a long time before an effective vaccine becomes available) or by individuals falling ill and recovering thereby developing natural immunity against the virus.

“Unfortunately, a very rough estimate suggests that we will only reach herd immunity to Covid-19 when approximately 60% of the population is immune (and remember that immunity is currently only reached by getting the infection as we have no vaccine!). The major downside is that this will mean that in the UK alone at least 36 million people will need to be infected and recover. It is almost impossible to predict what that will mean in terms of human costs but we are conservatively looking at 10,000s deaths, and possibly at 100,000s of death. The only way to make this work would be to spread out these millions of cases over a relatively long period of time so that the NHS does not get overwhelmed. Social distancing might contribute to this. Clearly the government believes that this process is manageable and building up herd immunity is the most effective way to stem Covid-19. I note that the UK is the only country in Europe that is following this strategy. Other countries also use scientific advice to guide their research and it is unclear to me why the UK is alone in their laissez-faire attitude to the virus. Perhaps the government has access to modelling data that suggests that the numbers I quoted above in numbers of cases and deaths are unavoidable in any scenario (e.g. even with prolonged social distancing strategies) but unfortunately these data, if they exist, have not been made available to the wider academic community so it is difficult to comment. However, last night’s U-turn banning large events suggests that the government’s policy is still very much subject to change. This change was perhaps influenced by the unprecedented outcry of scientists on the lax containment policy of the government.

snip



Prof Paul Hunter, Professor in Medicine, UEA, said:

“Immunity is when an individual has acquired resistance to infection with a particular pathogen (a virus, bacterium or parasite that causes disease) because they have already had an infection with that pathogen and recovered or have been immunised. Herd immunity occurs when a large enough proportion of a population are immune that an infection does not spread so easily or it can actually die out.

“In determining what level of herd immunity is necessary to stop the spread of infection we need to know the R0 (or reproductive ratio) this is the number of people that are likely to be infected by a single case when a new pathogen appears in a community with no prior immunity.

“So assume a pathogen with an R0=2, this means that after the first case there will be 2, then 4, then 8, etc. But by the time half the population is immune, on average half the people exposed from a single case will be immune and therefore only one person per infected person gets the infection.

“So the sequence 1, 2, 4, 8, 16, 32, 64, 128, 256 ….. becomes 1, 1, 1, 1, 1, 1, 1, 1, 1 and the disease will actually die out fairly quickly. Estimates of the R0 for COVID-19 vary somewhat but are in the order 2.0 to 3.0. Assuming that R0=3 then after about 66% of the population becomes infected then the virus will die out in the population.





Prof Matthew Baylis, Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, said:

“What is herd immunity? In a nutshell, everyone in a population is protected from infection before all of them are immune. The reason is that at a certain level of immunity (i.e., a proportion of people are immune, from having had the disease or having been vaccinated), the point comes when – on average – one infected person does not manage to contact and pass the infection on to one other person. Most of their contacts are already immune. The occasional contact is still susceptible, and the odd transmission event happens, but not often enough to sustain the disease. Transmission grinds to a halt, even though some or even many people have still not had the disease. This is herd immunity. It is one of the reasons boys are vaccinated against rubella: by vaccinating boys, boys are less likely to transmit to girls (an effect of immunity), and by vaccinating boys, girls are less likely to transmit to girls (an effect of herd immunity). For herd immunity, it does not matter whether the immunity comes from vaccination, or people having had the disease; people just need to be immune.

“A key question is how much immunity is needed before we get herd immunity? It varies per disease, depending on how transmissible it is. For a highly transmissible disease, like measles, on average one person might infect up 20 others, and herd immunity kicks in at 95% immune – and so, the target coverage for MMR vaccine is 95%. For flu, on average one person infects just 1.3 others; in this case herd immunity kicks in at about 25% immune or less; and so the target coverage for flu vaccine is much less than it is for measles (three quarters of over 65s).

“So what about COVID-19? Estimates are that one person may infect as many as 2-3 others, on average, meaning herd immunity should kick in at 50 – 67% of the population immune. And so in the absence of a vaccine, there would appear to be nothing to stop the spread of the virus until 50-67% of us have had it; and at that point herd immunity will kicks in and transmission will decline or stop. This is where the 60% of the population statistic has come from. And this is deeply concerning – taking the low fatality rate estimate of 1%, even 50% of the UK population infected by COVID-19 is an unthinkable level of mortality.





Dr Simon Gubbins, The Pirbright Institute, said:

“For a viral disease “herd immunity” refers to the indirect protection an uninfected individual receives if a proportion of the population is immune to infection. This could be achieved due to previous infection with the virus or more likely due to vaccination. The protection comes about because in a partially immune population infected individuals are less likely to encounter uninfected ones and so transmit the virus to them. Consequently, infection chains are interrupted and spread is stopped or slowed.

“The proportion of the population that needs to be immune for the number of new cases to decline depends on the basic reproductive ratio of the virus, known as R0. This is the average number of secondary cases that arise from each primary case when a virus is spreading in a wholly susceptible population.

“For SARS-CoV-2 estimates for R0 are around 2.5, so the proportion of the population that needs to be immune to achieve herd immunity is around 60%.

“Herd immunity acts as an evolutionary pressure for a virus to adapt so that it can escape immunity and can spread more easily. Influenza viruses are very good at this and frequently mutate to produce new strains to which people are not immune. This is the reason the seasonal flu vaccine needs to be updated annually. There is no information to show whether something similar will happen with SARS-CoV-2.”



Dr Ed Wright, Senior Lecturer in Microbiology, University of Sussex, said:

“Herd immunity is the required proportion of a population that needs to be immune to a pathogen to stop it from spreading within that same community. This immunity can be stimulated by vaccination or recovery following infection. The level of herd immunity required depends on how transmissible the pathogen is.

“This can be gauged from its basic reproduction number (R0) – the average number of people a positive case will go onto infect. For instance, to stop measles virus spreading within a population requires upwards of 90% of people to have immunity because the R0 for the measles virus is high (12-18) – it’s an airborne virus. The latest R0 for SARS-CoV-2 puts it between 2 and 3 so estimates suggest around 60% of the population would need immunity to stop the virus from taking hold in a community.”


snip

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Response to Celerity (Reply #9)

Wed Apr 8, 2020, 09:50 AM

13. Ok I bow to the experts: 60%.

"“So what about COVID-19? Estimates are that one person may infect as many as 2-3 others, on average, meaning herd immunity should kick in at 50 – 67% of the population immune. And so in the absence of a vaccine, there would appear to be nothing to stop the spread of the virus until 50-67% of us have had it; and at that point herd immunity will kicks in and transmission will decline or stop. This is where the 60% of the population statistic has come from. And this is deeply concerning – taking the low fatality rate estimate of 1%, even 50% of the UK population infected by COVID-19 is an unthinkable level of mortality."


For the US we are at: 401,636 out of 331,002,651 or about 0.12%.

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Response to Bluesaph (Original post)

Wed Apr 8, 2020, 04:59 AM

7. I just pray

This crap doesnt come back like the 1918 flu did in October of that fall.
Started out in spring much like C19 has, went down in summer, then roared
back worse in fall.
😥😥😥

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Response to MFM008 (Reply #7)

Wed Apr 8, 2020, 07:02 AM

10. A lot of that had to do with doughboys infecting then bringing new wave back from Europe

It was a worldwide pandemic, not just the US

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Response to Bluesaph (Original post)

Wed Apr 8, 2020, 08:13 AM

11. Idaho, near the Washington border here.

Been sick since March 12th. Horrible chest pain like broken ribs with this dog. No fever.

Was told flat out to forget testing in a scheduled phone appointment. They don't have testing abilities anyhow.

Have a real physical appointment for 4/21. Not expecting much.

I have a large family to take care of. I have to work and am in numerous public situations.

Getting to the point where the fuks stop giving, carrying on like a worker robot and smoking lots of grass. 27 days sick.

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Response to Bluesaph (Original post)

Wed Apr 8, 2020, 08:55 AM

12. You know, the Chinese doctors apparently noticed very early on

that this Coronavirus illness was a new thing. I imagine the doctors in the US are competent enough that someone would have recognized it as novel, if it really had been widespread here then.

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Response to Bluesaph (Original post)

Wed Apr 8, 2020, 09:52 AM

14. Without antibody testing it is all speculation, unfortunately

Are California's (known) case/death numbers slowing?

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Response to Bluesaph (Original post)

Wed Apr 8, 2020, 06:20 PM

17. In Portland 40% thought they had had Covid-19, but only 1 out 40 (2.5%) was positive

for having antibodies against the spike protein of Sars-ncov-2.
So many people are mistaken about having had it.
Other viruses could confer overlapping symptoms.




2 more had weak cross-reactivity.

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Response to Bluesaph (Original post)

Wed Apr 8, 2020, 07:00 PM

19. California car culture, naturally self distancing, everybody in their moving bubble

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