User:Kaban-kun/scratchpad

"Vaccine-resistant" organisms

 * http://www.healthmap.org/site/diseasedaily/article/first-cases-vaccine-resistant-whooping-cough-found-united-states-2813
 * the source cited does not appear to refer to "vaccine-resistance" at all: http://www.nejm.org/doi/full/10.1056/NEJMc1209369
 * http://www.cidrap.umn.edu/news-perspective/2013/02/researchers-find-first-us-evidence-vaccine-resistant-pertussis -- only headline refers to "vaccine-resistant" (VR).

Anti-vaccination movement

Occasionally people argue that vaccine usage should be curtailed, out of concern that widespread use of vaccines will create "vaccine-resistant" pathogens, in the same way that widespread use of antibiotics has led to the evolution of antibiotic resistant bacteria.

This concern seems reasonable and plausible, at least on a first look. However, when examined more closely, it fails to hold up. Antibiotics and vaccines work via completely different mechanisms, and it is this difference which makes even the label of "vaccine-resistant" misleading

When a patient takes an antibiotic to fight a bacterial infection, there is actual interaction between the antibiotic and the bacteria. Penicillins, for example, interfere with the peptidoglycans that make bacterial cell walls strong; the cell walls that have been so weakened burst under a difference in pressure. Occasionally, however, bacteria will mutate so that they form their peptidoglycan walls differently, and penicillins can no longer bind to and weaken these walls. This is one example of an antibiotic resistant mutation.

By contrast, there is no direct interaction between a vaccine and the pathogen it protects against. In many cases, the vaccine will have been gone from the system for years before the actual pathogen enters the patient's system; what isn't gone are the T-lymphocytes, the memory cells of the immune system, that were created when the vaccine made its earlier visit. When exposed to a vaccine, these memory cells "learn" particular antigens which are characteristic of the pathogen to be protected against. This is the same thing the immune system does on the first encounter with an actual pathogen; the difference is that when the first encounter is with the actual pathogen, the body's resources are under far more strain.

It is of course possible (probable is another question) for a pathogen to mutate so that it no longer exposes the antigens that the vaccine taught the immune system to recognize, and one could call that mutated strain of pathogen "vaccine-resistant" -- but the