Another herd immunity thread

[shuttlt]

I've read a few of the old threads on herd immunity and none of them quite seemed to pin it all down for me. I was hoping someone would be good enough to show me where the two camps disagree.

From what I can gather herd immunity can be stipped down to a mathematical argument:The_mathematics_of_mass_vaccination
I wondered whether there is anybody who feels the mathematics that herd immunity is based on is flawed?

If the maths isn't flawed, I wondered whether anybody disagreed with the numbers being pumped in?

If you don't disagree with the theory of herd immunity, I wondered if you disagreed with the figures for vaccination rates that pro-vaxers are forever claiming are too low?

One of the reasons this interests me so much is that most of the pro-vax position rests on herd immunity, which you folks regard as being obviously false. If you demolish it, you win. I kind of suspect since the pro-vax position is still the party line that in fact the herd immunity debate comes down to rival sources of authority for the numbers.

[kiara7]

I disagree with vaccine-induced herd immunity argument. There have been examples of natural herd immunity to diseases, i.e. chicken pox. The vast majority had it in childhood and developed natural lifelong immunity. Then adults are periodically re-exposed to it through their own children and grandchildren for natural boosters. That is the herd immunity.

Whether formulas and math are right or wrong is irrelevant. The pro-vax herd immunity argument is flawed because it's based on flawed assumptions that vaccines are 95 or 100% effective (which they are not), that viruses and bacteria don't mutate in order to survive (which they do), and that everyone will agree to take a possibility of damaging their child for the greater good and bring him to the "altar" for the sake of the herd (which many do not).

[shuttlt]

Originally Posted by kiara7

I disagree with vaccine-induced herd immunity argument. There have been examples of natural herd immunity to diseases, i.e. chicken pox. The vast majority had it in childhood and developed natural lifelong immunity. Then adults are periodically re-exposed to it through their own children and grandchildren for natural boosters. That is the herd immunity.

That would certainly be one form of it. I guess the same maths would describe what's going on there.

Originally Posted by kiara7

Whether formulas and math are right or wrong is irrelevant.

There is no question that it is irrelivant to why many people do not vax. It's relevant to me, as these are the terms in which I think. I would assume it's relevant to the wider debate between the two viewpoints. As I've said many times, I come from a naively pro-vax background and I would welcome having my world shaken.

Originally Posted by kiara7

The pro-vax herd immunity argument is flawed because it's based on flawed assumptions that vaccines are 95 or 100% effective (which they are not), that viruses and bacteria don't mutate in order to survive (which they do),

OK. So you disagree with the numbers going in to the formula? I'll try and flesh out the numbers relating to the official figures so we can be more specific about the disagreement.

Originally Posted by kiara7

and that everyone will agree to take a possibility of damaging their child for the greater good and bring him to the "altar" for the sake of the herd (which many do not).

OK. This is more like a disagreement with the official figures for vaccination rates. Do you disagree that, for the sake of argument, measles vaccination rates were above the critical herd immunity rate until recently in the UK? I presume you must in order to justify your statement.

[PaigeC]

That entry on wikipedia is very interesting (I : math). I agree with the mathematical analysis of it entirely - my problem is with the title. The major flaw is that it uses "vaccination" and "immunity" interchangeably. If you read the article as the mathematics of immunity it clearly explains the theory of active, natural herd immunity. This however does not translate into an accurate description of active, artificial immunity.

If we describe immunity as (from wikipedia): "Immunity is a medical term that describes a state of having sufficient biological defenses to avoid infection, disease, or other unwanted biological invasion." Then natural herd immunity postulates that in the presence of sufficient biological defenses in a critical mass of individuals a whole population will be protected. The logical leap can not be made that this automatically equates to sufficient vaccination rates in a critical mass...

Herd Immunity:
if individual immunity = or > critical mass then pathogen can not propagate ergo natural herd immunity.

is different than what pro-vax claims:
if # of vaccinated individuals = or > critical mass then pathogen can not propogate

This is missing a big variable: level of acquired immunity per individual. For herd immunity to be proven to me I would need:
if vaccinated individuals attain level x of active artificial immunity ("sufficient biological defense") AND these individuals make up (= or >) a required critical mass of the population then pathogen can not propagate ergo artificial herd immunity.

Sadly, wikipedia's entry on herd immunity does not even discuss the natural biologic process of herd immunity but only the theory of vaccine-induced herd immunity (in fact, it is hard to find information on herd immunity in a non-vaccine light anywhere online). The mix up (intentional or not) of vaccine and immune is a huge part of the divide between pro and anti-vax people IMO.

[runes]

It is fundamentally flawed to talk about herd immunity as a concept that is removed from specific vaccines/diseases. All vaccines don't work the same way, and the diseases have different criteria, incubation periods, contagious periods etc. that have a major impact on how it is spread.

For example, one major factor in smallpox "eradication" was quarantine, not vaccination. Since a person that has contracted smallpox is only contagious after the rash manifests, the case can be identified and quarantined in an appropriate and timely manner to reduce or eliminate transmission.

Other vaccines, like the DTaP, don't prevent transmission, because they are not supposedly building immunity against the bacteria that cause these diseases, but the toxins that this bacteria emit.

Also not being accounted for is live virus vaccines. As long as there are live virus vaccines, I personally believe that the disease will never be "eradicated", as shedding is a real concern.

And the article that you link to does mention shifting epidemiology:

However, it is important to consider this effect when vaccinating against diseases which increase in severity with age. A vaccination programme against such a disease that does not exceed qc may cause more deaths and complications than there were before the programme was brought into force as individuals will be catching the disease later in life. These unforeseen outcomes of a vaccination programme are called perverse effects.

although this is not a full analysis of the phenomenon. You can look for some information regarding measles, maternal antibodies and infants.

So the math that is in your link might be THEORETICALLY correct, but are not necessarily applicable in real life. And in the end, isn't that what really counts?

[kiara7]

The problem as PaigeC pointed out very clearly is the assumption that vaccine-induced "immunity" is the same as natural immunity. That is the first assumption that the rest of the argument is based on. This is false. The math may be right down the line, but based on a false assumption any conclusions are false too.

[shuttlt]

Originally Posted by PaigeC

Herd Immunity:
if individual immunity = or > critical mass then pathogen can not propagate ergo natural herd immunity.

is different than what pro-vax claims:
if # of vaccinated individuals = or > critical mass then pathogen can not propogate

I was concentrating mainly on measles where they seemed to be quoting very high rates:

Originally Posted by CDC

Most children who get the vaccine develop immunity to all three diseases (over 99% for measles and 95% for mumps and rubella). Protection is believed to be life-long.

http://www.cdc.gov/vaccines/vpd-vac/...cc_measles.pdf

Is this another case of I have my sources of authoritative facts, and you have yours?

Originally Posted by PaigeC

This is missing a big variable: level of acquired immunity per individual.

I'm going to have to go away, scratch my head and read more to be sure whether it's missing or significant. Right now I'm not certain one way or the other.

Originally Posted by PaigeC

Sadly, wikipedia's entry on herd immunity does not even discuss the natural biologic process of herd immunity but only the theory of vaccine-induced herd immunity (in fact, it is hard to find information on herd immunity in a non-vaccine light anywhere online). The mix up (intentional or not) of vaccine and immune is a huge part of the divide between pro and anti-vax people IMO.

That's kind of what I want nailing the maths to help me to understand.

[shuttlt]

Originally Posted by kiara7

The problem as PaigeC pointed out very clearly is the assumption that vaccine-induced "immunity" is the same as natural immunity.

And that's fine. Is this a fact that would be disputed, or accepted by the CDC?

Originally Posted by kiara7

That is the first assumption that the rest of the argument is based on. This is false.

I need to get the figures they are pumping into the formula to be absolutely sure what the mean by immunity.

Originally Posted by kiara7

The math may be right down the line, but based on a false assumption any conclusions are false too.

No arguing with that.

[shuttlt]

Originally Posted by kidspiration

It is fundamentally flawed to talk about herd immunity as a concept that is removed from specific vaccines/diseases.

OK. Measles is a topical one.

Originally Posted by kidspiration

Also not being accounted for is live virus vaccines. As long as there are live virus vaccines, I personally believe that the disease will never be "eradicated", as shedding is a real concern.

Is measles in MMR live virus? I've got an idea it is.

Originally Posted by kidspiration

And the article that you link to does mention shifting epidemiology:

Sure, that is an acknowledged problem with vaccination programs that fail to reach herd immunity. I don't think that is disputed.

Originally Posted by kidspiration

So the math that is in your link might be THEORETICALLY correct, but are not necessarily applicable in real life. And in the end, isn't that what really counts?

The maths, as I understand it is what the pro-vax case is based on. I want to understand why it is wrong. Sure the real world is what counts, but it is wooly and ill defined, arguments about it can go on and on without ever getting anywhere. Some aspects can be expressed in terms of maths, the real question is, are those aspects important.

[alegna]

Also, it's important to remember, that herd immunity can only apply to diseases where the vaccine prevents transmission.

-Angela

[shuttlt]

Originally Posted by alegna

Also, it's important to remember, that herd immunity can only apply to diseases where the vaccine prevents transmission.

-Angela

Agreed. No herd immunity for tetinus.

[shuttlt]

Originally Posted by kidspiration

Also not being accounted for is live virus vaccines. As long as there are live virus vaccines, I personally believe that the disease will never be "eradicated", as shedding is a real concern.

In as much as so long as there is a possibility of secondary transmission the disease won't be eradicated, I agree. I disagree that this isn't taken account in the maths. A secondary transmission is just a case of infection that may, or may not manage to infect >=1 other person and start an outbreak.

[kiara7]

Originally Posted by shuttlt

The maths, as I understand it is what the pro-vax case is based on. I want to understand why it is wrong. Sure the real world is what counts, but it is wooly and ill defined, arguments about it can go on and on without ever getting anywhere. Some aspects can be expressed in terms of maths, the real question is, are those aspects important.

We need to figure out the difference between natural immunity and vaccine immunity, in numbers. I don't have time to look this up, but if you're up for it, I'm sure we'll have a very good discussion.

[shuttlt]

Originally Posted by kiara7

We need to figure out the difference between natural immunity and vaccine immunity, in numbers. I don't have time to look this up, but if you're up for it, I'm sure we'll have a very good discussion.

If I turn some numbers up, I'll most definately post them. You all probably have the advantage of me on finding them as there being a difference is fairly new on me. People keep talking as if artifical immunity fades, but that isn't what the CDC says (as previously quoted):

Originally Posted by CDC

Most children who get the vaccine develop immunity to all three diseases (over 99% for measles and 95% for mumps and rubella). Protection is believed to be life-long.

If it's lifelong and 99% effective (in the case of measles), I don't see where there is much room for a natural immunity to do much better. Perhaps, how many children they mean by 'most' is where the difference lies?

[anewmama]

Originally Posted by shuttlt

One of the reasons this interests me so much is that most of the pro-vax position rests on herd immunity, which you folks regard as being obviously false.

I don't think it is absolutely false. I think there are flaws and questions, but I don't think I could ever throw it out entirely as some have.

[shuttlt]

Apologies for the storm of posts. I realized I'm confused about something:
"Most children who get the vaccine develop immunity to all three diseases (over 99% for measles and 95% for mumps and rubella). "
Does this mean most children are 99% protected, or 99% of children are completely protected? I'm looking, but the CDC faq didn't make it clear.

[anewmama]

Originally Posted by kiara7

There have been examples of natural herd immunity to diseases, i.e. chicken pox. The vast majority had it in childhood and developed natural lifelong immunity. Then adults are periodically re-exposed to it through their own children and grandchildren for natural boosters. That is the herd immunity.

I don't disagree with the idea that children get it and adults' immunity is reinforced. But there is no herd immunity here in my opinion because it is still a circulating disease which children get. Or should I say was before the vax?

The way it used to work the way I see it is there was only partial herd immunity with adults carrying on immunity after childhood exposure. The only part of the herd being mostly protected is adults. But the idea that adults are immune and that might protect kids doesn't work so there is no total herd immunity. Or was. Hard to talk about this one as there is a vax!

[runes]

Originally Posted by shuttlt

Is measles in MMR live virus? I've got an idea it is.

Yes. All 3 in the MMR...measles, mumps and rubella, are live virus vaccines.

As is varicella (chicken pox), rotovirus, oral polio and Flumist.

Originally Posted by shuttlt

Sure, that is an acknowledged problem with vaccination programs that fail to reach herd immunity. I don't think that is disputed.

Shifting epidemiology occurs whether the vaccine program "reaches" herd immunity or not. Case in point...chicken pox.

Originally Posted by shuttlt

The maths, as I understand it is what the pro-vax case is based on. I want to understand why it is wrong. Sure the real world is what counts, but it is wooly and ill defined, arguments about it can go on and on without ever getting anywhere. Some aspects can be expressed in terms of maths, the real question is, are those aspects important.

If you are asking if the key concepts of epidemiology can be boiled down to the math, and if this math is either correct or relevant, my original assertion still stands. It is a lot more complicated than a bunch of mathematical formulae.

For example, how do they account for asymptomatic and subclinical cases? Certainly they won't figure in the math, and they won't count as a clinical "case" but it sure does factor into the epidemiology.

If you are planning to vax for the MMR, are you going to get titres drawn after vaccination and every year afterward to see if your child is immune? Why or why not?

[shuttlt]

Originally Posted by anewmama

I don't think it is absolutely false. I think there are flaws and questions, but I don't think I could ever throw it out entirely as some have.

Apologies, it can be a little too easy to tar everybody with the same brush. The spectrum here goes from the odd pro-vaxer right the way to people who don't subscribe to the conventional model of disease.

[alegna]

Originally Posted by shuttlt

Agreed. No herd immunity for tetinus.

(Right, since tetanus isn't a communicable disease in the first place )


Or pertussis.

Or probably diphtheria

Or polio with the current vax.

-Angela