The "myth" of herd immunity

[JoeTheJuggler]

I have an antivaxxer on my FB page who insists that herd immunity is a myth, because vaccines wear off over time and people aren't protected by their vaccine induced antibodies after several years.

Isn't that like arguing that condoms aren't very effective if you try to re-use them?

I think your antivaxxer assumes that herd immunity only comes from life-long immunity. It comes from the fact that I as an individual, even if I'm not vaccinated, stand a better chance of getting through the flu season without getting infected if a substantial part of the population--the people in my community-- doesn't get sick and infect me.

WRT to flu, the viruses change so frequently, that lifelong immunity isn't a goal anyway. That's why you get a new seasonal flu vaccine every year.

The lifelong accumulation of antibodies (through vaccinations and from living through infections) is probably what makes older folks less likely to get sick with H1N1. But that's not what "herd immunity" refers to.

 

[JoeTheJuggler]

Herd immunity doesn't exist? Strange, lets ask someone with smallpox about it...

Well said. I'm more verbose, so I'll spell this out a bit more. . .

The reason I personally never got smallpox was not that I personally was vaccinated against it (I wasn't), but because the disease was already virtually wiped out of the human population (thanks to vaccination programs) before I came along.

I'm benefiting from herd immunity and not personal immunity.

 

[Ixion]

Yeah, I'm pretty sure she does.

LIke I said, awesome post. We love posters like you who know their stuff, and I totally enjoyed reading. Feel free to get carried away as much as you like!

Thank you.

As for Herpevac, I checked the clinical trial. It is supposed to end this month: http://clinicaltrials.gov/ct2/show/NCT00057330.

Then, GlaxoSmithKline will have to finish FDA approval and start production and marketing. Probably 3 years minimum. At least downgrading disease in women is a good first step towards establishing herd immunity for Simplex II.

 

[Hooloovoo]

There's so much good stuff here. Thank you all. What I knew about herd immunity and antibodies didn't go much past what I learned in high school physiology, most of which I've long forgotten. It's time to get myself educated, so I can better respond to this crap.

 

[EvilSmurf]

Then, GlaxoSmithKline will have to finish FDA approval and start production and marketing. Probably 3 years minimum. At least downgrading disease in women is a good first step towards establishing herd immunity for Simplex II.

I feel a [rule10]storm a-coming from the usual religious right suspects if someone recommends that vaccine be given in a standard vaccination schedule.

 

[Hooloovoo]

Herd immunity doesn't exist? Strange, lets ask someone with smallpox about it...
MrQ

I know. It's silly, huh? Herd immunity is something that's so obvious, but I felt like I should be a good little skeptic and ask around.

Antivaxxers don't consider that vaccinated people are still exposed to the viruses and bacteria, but because of their immune status can get subclinical infections which then boosts their immune system. Also, the immune response is normally measured by antibody levels which do wane over time, but it's the memory B and T cells that provide immunological memory and these are not measured. If the immune response wanes then middle aged people would be getting measles and mumps etc wouldn't they?

This is excellent information. As far as I knew, a person had to have antibodies to retain immunity. Do these B and T cells last for a person's entire life?

CMI = Cell-mediated immunity.

It is the other branch of the adaptive immune system. One branch, the humoral response, makes antibodies, which mainly seek to neutralize extracellular pathogens, such as bacteria. The other branch, CMI, utilizes specialty cells to recognize infected cells (such as virally infected cells) or malfunctioning cells (such as cancer) and eliminate them before the problem spreads.

Neato. This stuff gets more interesting all the time.

 

[Eos of the Eons]

I feel a [rule10]storm a-coming from the usual religious right suspects if someone recommends that vaccine be given in a standard vaccination schedule.

Yeah, cuz the threat of HIV, bacterial infections, and pregnancy all dissappear when you get vaccinated against HPV and Herpes Simplex! Can't have people thinking they can have teh relations!

 

[rjh01]

Without doing any mathematics.
Instead of vaccinating people, lets say we shoot them.

Take a group of 100 and shoot 99.
Supposing number 100 doesn't already have the virus, given that person-person contact is the sole, or major vector.
Did his chance of catching it just go up or not?

How (from the POV of the virus) does vaccinating those people differ from shooting them?

Can you fight the spread of fire by removing potential fuel?
Yes. Foresters do so daily, by thinning undergrowth, even when no fires are burning.
Maybe that's a better metaphor?

I do not think anyone has answered this post. The chances of getting a disease depends on how many people you meet who might have the disease. If you shoot 99% of the people but the remaining 1% still meet the same number of people then you have done nothing to stop the disease. If instead you reduce the number of people you meet by 99% who might have the disease then you reduce the chances of getting the disease by 99%. But it does not end there. After some time the % of people who can spread the disease goes down further reducing your chances of getting the disease.

Of course hermits and people who live in isolated communities will never get infectious disease either as they never meet other people.

 

[Hooloovoo]

I feel a [rule10]storm a-coming from the usual religious right suspects if someone recommends that vaccine be given in a standard vaccination schedule.

A shot to prevent the wrath of Almighty God from raining down upon the genitals of the sinful. He can be thwarted by nerds in lab coats. Keep thwarting, nerdy warriors!

 

[Travis]

I'm not understanding why an anti-vaxxer would make this argument. If there is no herd immunity wouldn't that mean we need to get more people vaccinated simultaneously?

 

[Eos of the Eons]

no no no no no... it means vaxxes are more useless than doing nothing, so don't bother with them. Their ultimate agenda is to get everyone to stop using them and buy crap like magic oils, water, and overdose on their supplements (just go to any antivaxxer office and see all their wares).

 

[Capsid]

This is excellent information. As far as I knew, a person had to have antibodies to retain immunity. Do these B and T cells last for a person's entire life?

It's still not that well understood. For memory cells to be maintained, it's thought they need exposure to the antigen. But people vaccinated with smallpox years ago (~50 years!) still seem to have good immune memory without exposure to the virus.

Another example is during measles outbreaks. The majority who get infected are the unvaccinated, if immunity to the vaccine waned you should expect the vaccinated adults to get infected too.

 

[Elvis666]

CMI = Cell-mediated immunity.

It is the other branch of the adaptive immune system. One branch, the humoral response, makes antibodies, which mainly seek to neutralize extracellular pathogens, such as bacteria. The other branch, CMI, utilizes specialty cells to recognize infected cells (such as virally infected cells) or malfunctioning cells (such as cancer) and eliminate them before the problem spreads.

Thanks, Ixion. This stuff is one of the main reasons I read this forum.

 

[Ixion]

It's still not that well understood. For memory cells to be maintained, it's thought they need exposure to the antigen. But people vaccinated with smallpox years ago (~50 years!) still seem to have good immune memory without exposure to the virus.

Another example is during measles outbreaks. The majority who get infected are the unvaccinated, if immunity to the vaccine waned you should expect the vaccinated adults to get infected too.

Exactly. I dabble a bit with memory T cells in my laboratory, but not to the depths that some of my colleagues do. Very complicated.

 

[Almo]

Thanks, Ixion. This stuff is one of the main reasons I read this forum.

Seconded.

 

[Ixion]

I love that the forum has so many intelligent and informed people on it. I learn new things all the time.

As MrQuest and JoetheJuggler pointed out, diseases like measles and smallpox make herd immunity more noticeable because there is no other vector for them. In other words, the only way you can get the disease is from another human. In populations with a large vaccinated group, the disease doesn't get very far, but in non-immunized populations it can be crippling.

For some other diseases that are carried by other vectors, like mosquitoes, the possibility of getting the disease is more dependent on if you had been vaccinated than if you had not and somebody else had.

 

[Hooloovoo]

It's still not that well understood. For memory cells to be maintained, it's thought they need exposure to the antigen. But people vaccinated with smallpox years ago (~50 years!) still seem to have good immune memory without exposure to the virus.

Another example is during measles outbreaks. The majority who get infected are the unvaccinated, if immunity to the vaccine waned you should expect the vaccinated adults to get infected too.

Fascinating stuff! Again, thanks to you all for this information. I'm with Elvis666. I've learned more on this forum than nearly anywhere else.

 

[Hooloovoo]

I'm not understanding why an anti-vaxxer would make this argument. If there is no herd immunity wouldn't that mean we need to get more people vaccinated simultaneously?

Yeah, it would. It makes about as much sense as any antivax argument.

 

[Estellea]

I'm not understanding why an anti-vaxxer would make this argument. If there is no herd immunity wouldn't that mean we need to get more people vaccinated simultaneously?

Anti-vaxers deny herd immunity for a variety of reasons but I think the primary one is that they are free-riders and know it. Thus, if herd immunity doesn't exist, their non-contribution, as it were, doesn't matter.

 

[Skeptic Ginger]

...Like
For some other diseases that are carried by other vectors, like mosquitoes, the possibility of getting the disease is more dependent on if you had been vaccinated than if you had not and somebody else had.

Likewise, tetanus which requires common soil bacteria to enter a puncture wound where it grows best in the absence of atmospheric oxygen.

Rabies also readily comes to mind as a risk independent of human herd immunity, but dependent on animal prevalence plus the person getting vaccinated if exposed.