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Since bacteria can evolve to overcome antibiotic use, why wouldn't they be able to evolve to overcome antibody or cell-mediated immunity?

(One possible explanation: antibiotics have only one target while vaccines elicit antibodies against multiple targets and multiple T-cell epitopes. Even more targets arise when comparing sub-unit vs inactivated vaccines, where the number of targets are extremely higher using inactivated vaccines, containing whole bacterial cell.)

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    $\begingroup$ why wouldn't be able to evolve to overcome antibody or cell-mediated immunity?...They can; Vaccines are not 100% effective. In some cases they are quite efficient. $\endgroup$ – WYSIWYG Mar 5 '15 at 13:11
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    $\begingroup$ In vaccine development today you try to choose evolutionary conserved targets for the vaccine to prevent this. $\endgroup$ – Chris Mar 5 '15 at 13:19
  • $\begingroup$ Thanks @WYSIWYG, it would be great if someone could give some reasons. $\endgroup$ – biotech Mar 5 '15 at 13:42
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    $\begingroup$ Actually most of the nowadays vaccines activate B-cells and not T-cells. Ofc. there can be resistance to vaccines, e.g. by influenza. Bacterias have more complex surface than viruses, that's why they cannot change their surface as fast as it would be necessary to overcome vaccines. $\endgroup$ – inf3rno Mar 5 '15 at 16:35
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    $\begingroup$ One major difference is that vaccine acts in human host while antibiotics act on pathogen. Antibiotics target a specific pathway in the pathogen while vaccines sensitize humans to all the antigens present in it. $\endgroup$ – One Face Mar 6 '15 at 1:50
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Unfortunately, we do see examples of bacteria and viruses evolving vaccine resistance. For instance, vaccine resistant strains of polio and pertussis have recently been identified.

Yet these seem like the exception rather than the rule. One thing that makes it harder for pathogens to evolve resistance is that vaccines usually generate antibodies to multiple antigens, all of which the pathogen would have to alter.

Another reason vaccines tend not to drive vaccine resistance is that the diseases for which we vaccinate are typically those that are not antigenically variable. (Haemophilus influenza is a notable exception; there we use a conjugate vaccine). This may have something to do with how we view vaccine efficacy. For example, we don't say that the influenza virus evolves vaccine resistance--yet we need a new vaccination each year due to antigenic shift.

If you are interested in learning more, Angela McLean has a nice article looking into this question.

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  • $\begingroup$ There is another reason why Hib is a conjugate vaccine: The polysaccherid from the capsule alone only triggers a relatively weak immune response. The antigen which is used for the coupled vaccine (often tetanus toxoid) makes the answer much stronger. $\endgroup$ – Chris Mar 5 '15 at 18:27
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    $\begingroup$ Influenza vaccines are renewed annually because the viruses change continuously and thus become resistant to most antibodies people develop, vaccine-induced or not. HI virus (AIDS) also changes so often that vaccines are extremely ineffective against it. $\endgroup$ – Archimedix Mar 7 '15 at 6:53
  • $\begingroup$ @Archimedix: Exactly -- yet we don't say that influenza viruses evolve vaccine (or acquired immunity) resistance. We just talk about antigenic shift. So it's not so much that immune resistance doesn't evolve, it's that we call it something else. You make an important point: HIV is good example of a virus where this evolution occurs within a single host during the duration of an infection. $\endgroup$ – Corvus Mar 7 '15 at 7:25
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    $\begingroup$ Also it is noteworthy that the general idea behind vaccines is to "train" your own immune system to the pathogens. Since we are all different a little bit we produce a little bit different antibodies therefore the pathogens do not have a general counter-strategy or selective pressure compared to antibiotics. $\endgroup$ – Nandor Poka Feb 24 at 19:36

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