Herd immunity not possible without a vaccine.

[bibbitybobbitycats]

I have been doing a bit of reading about herd immunity, as I wasn't sure I understood the concept properly.

One thing that I didn't realise is that control of an infectious disease without a vaccine has never been achieved before (according to this article):

theconversation.com/can-we-actually-learn-to-live-with-coronavirus-not-until-we-have-a-vaccine-147792

I did wonder if this was completely true, as if so, how did the plague die out? This is informative:

www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)31924-3/fulltext

Which says that herd immunity to plague, malaria, and typhus occurred because people "no longer lived in close association with the requisite vectors" (for example fleas, dirty water). It also says that without a vaccine, many people would have to die from COVID-19 before population immunity is achieved.

It would seem that to achieve herd immunity without a vaccine we would need around 47 million people to be infected with the virus. Obviously, this would lead to tens of thousands, maybe hundreds of thousands of deaths and would leave many people with health problems.

So why do some people think trying to achieve herd immunity without a vaccine is a viable, ethical policy? What am I missing?

"One thing that I didn't realise is that control of an infectious disease without a vaccine has never been achieved before should read One thing that I didn't realise is that control of an infectious disease through population immunity without a vaccine has never been achieved before*

Before I say this I want to make it clear I am not an expert, I am not claiming to be, I just studied history. Secondly I do not believe covid is going to just disappear without a vaccine.
However, in Tudor times there was a disease called 'sweating sickness' or 'the sweat' or 'the english sweat' it was as far as I know a hantavirus, it killed many many people it was very contagious could kill within a day or two. It disappeared of its own accord .

Oh yes, that's mentioned in Wolf Hall. I wonder if there are other examples of diseases vanishing. Didn't the Orange One predict that will happen with Covid?

Agree OP as do many eminent scientists
www.johnsnowmemo.com/

I understand that the Spanish flu in 1918 lasted for about 18 months and then faded away / became a normal part of the flu season. There was never a vaccine.

Oh, hantaviruses are carried by rats etc. Maybe that is part of the explanation for it vanishing - could the rats have become immune and so stopped infecting people?

I’m not sure how herd immunity could work for Covid , immunity estimates between 60-90 days

The OP is contradictory. Says HI is impossible without a vaccine but also says ‘without a vaccine, many people would have to die from COVID-19 before population immunity is achieved’

?

The answer is we don’t know at this stage whether HI is possible without a vaccine. But thus far, there have been precious few reinfections.

@Toebarb

I understand that the Spanish flu in 1918 lasted for about 18 months and then faded away / became a normal part of the flu season. There was never a vaccine.

But the Spanish flu still exists (or its descendants) and is incorporated in the current vaccines. Also, many older people had immuity because of exposure to other flu viruses. Covid is a novel virus so not comparable.

@MummyPop00

The OP is contradictory. Says HI is impossible without a vaccine but also says ‘without a vaccine, many people would have to die from COVID-19 before population immunity is achieved’

?

The answer is we don’t know at this stage whether HI is possible without a vaccine. But thus far, there have been precious few reinfections.

OK, I should have phrased better. Even if it were possible to achieve herd immunity, we would need 47 million people to be infected etc.

yeah, I don't think herd immunity exists for covid. Not in the sense of "stop people getting it"

there was a good radio programme on last night... Naked Scientist? or 5am slot. About how there will be probably increased resistance to getting severe disease with each infection (increased on avg, in population not necessarily in every individual). To the point that you might get covid dozens of times in your life but the last dozen times will be asymptomatic. So the vaccine is to help elderly at risk of terrible illness, not to stop their illness at all. The vaccination programme may only run for 10 yrs (annual jabs) & then be quietly dropped.

@mightyducks

I’m not sure how herd immunity could work for Covid , immunity estimates between 60-90 days

Not true at all.

If it were true (it's not), then a vaccine would also only last 60-90 days.

Isn't the plague treated with antibiotics now? It does still pop up here and there I think

The answer is we don’t know at this stage whether HI is possible without a vaccine

And as there doesn't seem to be any precedent for HI without a vaccine, it would be unethical to go down that road?

Which says that herd immunity to plague, malaria, and typhus occurred because people "no longer lived in close association with the requisite vectors" (for example fleas, dirty water)

But surely that's NOT herd immunity, is it? The people weren't immune, they just avoided/eliminated the source of infection.

From the first article you quoted: Sars went round the world twice between November 2002 and May 2004 before disappearing altogether. This was thanks to stringent control measures, such as quarantine for contacts of people with the infection and regular deep cleaning of public areas.

So it actually gives an example of a disease that was controlled without a vaccine (or herd immunity, either.)

As I understand it the plague died out because the black rats that carried the disease were killed out by brown rats (which we have today), brown rats are more timid and so don't mix with people, so didn't give us plague flees.

Spanish flu mutated to become flu we know today.

When people say herd immunity I didn't think they meant it would go away. I assumed it meant enough people would be immune or not be badly effected so that we don't have a pandemic of people all falling ill at once. It would behave in the same was as chicken pox or flu in that managageble numbers of people get seriously ill from it.

@user1495884620

From the first article you quoted: Sars went round the world twice between November 2002 and May 2004 before disappearing altogether. This was thanks to stringent control measures, such as quarantine for contacts of people with the infection and regular deep cleaning of public areas.

So it actually gives an example of a disease that was controlled without a vaccine (or herd immunity, either.)

Yes, exactly. We can't control the spread through herd immunity because there is no vaccine, so the only choice is some form of restrictions.

I see what you are getting at now. Maybe read up a bit on measles which is probably a good example of how herd immunitiy protects without eliminating. Before vaccines, in the old world, most people would get measles, probably as a child, and some would die but once you'd had it you were immune and the world lived with it. When Europeans went to America, they brought measles and other diseases with them. Whole peoples were wiped out because they had no immunity to these diseases whatsoever.

Bubonic plague still exists and does pop up in various places, but it is a bacterial disease, so can be controlled with antibiotics.

Yes, exactly. We can't control the spread through herd immunity because there is no vaccine, so the only choice is some form of restrictions.

Tbf we can't control the spread of flu either and we have a sort of vaccine for that. We may just need to accept covid as a part of life.

Herd immunity isn't somthing you can guarantee without a fool proof vaccine like we had for somthing like small pox. So no without one we won't ever irradicate coivd.

But, once most people have had covid, their immune systems should be more primed to deal with further infections. So more people would be uneffevted by it and so less contagious. It would then probably act like flu in that it take down a few thousand elderly and vulnerable each year.

We may find that the young people that have it now will not be
vulnerable to it when they are older. Unfortunately we can't really predict what will happen naturally. We can only hope that it mutates to become more like the coronavirus' we are used to like cold.

@user1495884620

I see what you are getting at now. Maybe read up a bit on measles which is probably a good example of how herd immunitiy protects without eliminating. Before vaccines, in the old world, most people would get measles, probably as a child, and some would die but once you'd had it you were immune and the world lived with it. When Europeans went to America, they brought measles and other diseases with them. Whole peoples were wiped out because they had no immunity to these diseases whatsoever.

I had measles in the days before the vaccine!

What I don't understand is why some people think HI is a viable policy for this disease in the absence of a vaccine.

Interesting little article in this morning's Observer as to how pandemics resolve over time.
www.theguardian.com/commentisfree/2020/oct/18/how-do-pandemics-end-in-different-ways-but-its-never-quick-and-never-neat

I did wonder if this was completely true, as if so, how did the plague die out?

It didn't. It came back several times but is no longer a problem in the developed world because of antibiotics. Antibiotics only work on bacteria, we have no comparable broad-spectrum drugs to treat viruses.

One thing that I didn't realise is that control of an infectious disease through population immunity without a vaccine has never been achieved before

I think you are misunderstanding a little what herd immunity means in this context, OP.

We've managed to wipe out one virus in the whole of human history- smallpox. This was achieved by huge scale vaccination programs until the virus literally had no-where to spread.

But smallpox immunity is persistent, Covid-19 won't be, so there is no chance of everyone getting it and then it stops. We will not be able to eliminate it, even with a vaccine.

There are hundreds of viruses similar to Covid which are collectively referred to as cold/flu. Some of these are almost as deadly as Covid, yet even in years where we get a really bad one and miss it in the vaccination program it typically won't kill more than about 25k.

This is because we already have herd immunity. Many people in the population will have had that virus or a related strain, so the R number is not high enough for it to rage unchecked like Covid has. Over summer it then dies off again and if it's still around next year it would be included in the annual vaccine.

The biggest reason Covid is so bad is because it's new and we have little or no pre-existing immunity.

This is what we are trying to do with Covid- vaccinate the vulnerable while the rest of the population gets it so that, over several years, it becomes part of the normal resevoir of flus.

What I don't understand is why some people think HI is a viable policy for this disease in the absence of a vaccine.

I think most of them fundamentally don't understand how high the death rate will be if we can't get people in ICU quickly when they start struggling to breathe.

I also think they don't get that the economy will shut down far worse than it has once the disease is wildly uncontrolled.

A lot of them are just conspiracy nutters anyway or people losing jobs who are desperate for a magic solution.