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Why does drug resistance easily evolve but vaccine resistance does not?

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Re: Why does drug resistance easily evolve but vaccine resistance does not?

#11

Post by mannykannot »

While I do not doubt that this difference exists in general, I am wondering if there is not, to some extent, an issue of terminology here. My understanding is that influenza vaccination is somewhat uncertain because antigenic shift and drift produces new, or not-recently-seen, strains. When a bacterium modifies its genome to survive an antimicrobial drug, we call that 'resistance', yet I guess the drug is still as effective as before against unmodified bacteria. While the mechanism is, in detail, different in the two cases, they both involve the pathogen modifying its genome to render the treatment less effective.

Maybe the distinction is because, in the case of influenza, the strain changes are not in response to, and driven by, the treatment? HIV, however, seems to be very effective in mutating specifically in response to every candidate vaccine that has been tried against it.

Re: Why does drug resistance easily evolve but vaccine resistance does not?

#12

Post by m3kw9 »

mannykannot wrote: post #11

While I do not doubt that this difference exists in general, I am wondering if there is not, to some extent, an issue of terminology here. My understanding is that influenza vaccination is somewhat uncertain because antigenic shift and drift produces new, or not-recently-seen, strains. When a bacterium modifies its genome to survive an antimicrobial drug, we call that 'resistance', yet I guess the drug is still as ef…

Exatly, the resistance due to evolution and new strains by passing vaccines is not very comparable

Re: Why does drug resistance easily evolve but vaccine resistance does not?

#13

Post by ianai »

m3kw9 wrote: post #12
mannykannot wrote: post #11

While I do not doubt that this difference exists in general, I am wondering if there is not, to some extent, an issue of terminology here. My understanding is that influenza vaccination is somewhat uncertain because antigenic shift and drift produces new, or not-recently-seen, strains. When a bacterium modifies its genome to survive an antimicrobial drug, we call that 'resistance', yet I guess the drug is still as ef…

Exatly, the resistance due to evolution and new strains by passing vaccines is not very comparable

As a total amateur, it seems like the bacterial/viruses need only find one way to breakthrough your immunity. Your immune system has many more attack vectors to cover. The bacteria only need to be right once, but the immune system billions.

Re: Why does drug resistance easily evolve but vaccine resistance does not?

#14

Post by epmaybe »

philjohn wrote: post #6
dnautics wrote: post #5

The decreasing effectiveness of the flu vaccine suggests to me that the flu metagenome is evolving resistance to our vaccine generation strategy.

It's not, each year we have to guess which strains will be prevalent, and sometimes they get it wrong.

That brings up an interesting question: what does the CDC do to predict strain prevalence each year?

Re: Why does drug resistance easily evolve but vaccine resistance does not?

#15

Post by alextheparrot »

ianai wrote: post #13
m3kw9 wrote: post #12

Earlier quoted context omitted.

Exatly, the resistance due to evolution and new strains by passing vaccines is not very comparable

As a total amateur, it seems like the bacterial/viruses need only find one way to breakthrough your immunity. Your immune system has many more attack vectors to cover. The bacteria only need to be right once, but the immune system billions.

The immune system is also layered - a single viral infection won’t necessarily kill you right away. If it does penetrate the initial layers, the immune system will continue adapting and fighting it on each new front. Eventually your entire body might even engage using things like a fever. In this way, it doesn’t need to be right initially billions of times, but capable once at one of many steps.

Re: Why does drug resistance easily evolve but vaccine resistance does not?

#16

Post by icegreentea2 »

epmaybe wrote: post #14
philjohn wrote: post #6

Earlier quoted context omitted.

It's not, each year we have to guess which strains will be prevalent, and sometimes they get it wrong.

That brings up an interesting question: what does the CDC do to predict strain prevalence each year?

They're tell you!

https://www.cdc.gov/flu/about/season/vaccine-selection.htm

Ars Technica also did a nice breakdown (with many related Q&As)

https://arstechnica.com/science/2017/12/this-years-flu-seaso...

Re: Why does drug resistance easily evolve but vaccine resistance does not?

#17

Post by paviva »

Very good question and a very good answers in this article!

I'll add one more reason not explored by the authors: antibodies don't "leak" in the environment, in contrast to the antibiotics which are everywhere.

For example, if I'm vaccinated against S. pneumoniae (one of the bacteria that can cause pneumonia), the bacteria have to get inside my body to gain exposure to my vaccine-induced antibodies. This makes the emergence of resistance very unlikely because :

(1) the number of bacteria that are exposed to the antibody is relatively small, because the antibody response is pretty fast and happens before the bacteria had a chance to multiply to significant numbers; (2) any bacteria clones who evolve resistance to the antibody remain susceptible to the myriad of other immunes peptides, to macrophages, and so on. In other words, as long as I survive my pneumonia, no resistance can ever emerge, because I will kill all the resistant clones through other means.

Contrast this to antibiotics. I have pneumonia, I take antibiotics, I'm cured. However, I excrete those antibiotics in urine and stool. Outside of my body, enormous numbers of bacteria are exposed to minute doses of antibiotics. The number of surviving clones is likely to be very high, and those survivors do not face any supplemental threat. Thus, resistance to that antibiotic can be transmitted to later generations.

Re: Why does drug resistance easily evolve but vaccine resistance does not?

#18

Post by Xylakant »

lr4444lr wrote: post #10

Not a biologist here, but hoping maybe one can correct me on this: isn't it an important factor that in the immune system the signaling cells themselves have evolved to respond to variants of a given pathogen's protein marker, whereas drugs are always presenting the same chemical challenge?

As far as I read the article and understand your question, this is indeed one of the factors that they mention. Each persons immune system reacts in a different way, posing a unique challenge to the pathogen.

Re: Why does drug resistance easily evolve but vaccine resistance does not?

#19

Post by rflrob »

philjohn wrote: post #6
dnautics wrote: post #5

The decreasing effectiveness of the flu vaccine suggests to me that the flu metagenome is evolving resistance to our vaccine generation strategy.

It's not, each year we have to guess which strains will be prevalent, and sometimes they get it wrong.

Not only that, the strains they choose not to include will likely spread more effectively than the ones that they do. So even if the vaccine magically protected 100% of people against the most prevalent N strains, the (N+1)th strain will be the one that most people get. Did the CDC “guess wrong”, or are they doing their best to fight an impossible battle?

Re: Why does drug resistance easily evolve but vaccine resistance does not?

#20

Post by pishpash »

paviva wrote: post #17

Very good question and a very good answers in this article! I'll add one more reason not explored by the authors: antibodies don't "leak" in the environment, in contrast to the antibiotics which are everywhere. For example, if I'm vaccinated against S. pneumoniae (one of the bacteria that can cause pneumonia), the bacteria have to get inside my body to gain exposure to my vaccine-induced antibodies. This makes the em…

You don't excrete antibodies? I think you might be saying that antibiotics are passive strategies which are inherently overly broad and thus problematic.
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