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Vaccines. what exactly is the significance of using killed microbes

  1. Jul 30, 2011 #1
    vaccine may contain attenuated microorganisms, killed microorganisms or toxoids.
    Certain vaccines contain attenuated forms or killed forms or toxoids.

    For example, in case of cholera, rabies, hepatitis B, Japanese encephalitis, we use killed form. Why can't we form attenuated forms here? Is it because the diseases are so deadly that usage of attenuated forms can cause the death of the recipient of the vaccine. But, if it is attenuated isn't it true that the life form has lost it's toxic properties and is still being able to produce antibodies?

    So what exactly is the significance of using killed microbes for these particular diseases?
     
    Last edited by a moderator: Jul 30, 2011
  2. jcsd
  3. Jul 30, 2011 #2

    Ryan_m_b

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    Staff: Mentor

    Re: vaccines

    One of the reason could be that there is too much danger in using attenuated forms. Back in my undergrad immunology modules I remember being taught that there is always a small chance that a batch will contain a fully capable organism. Reasons for this were almost always industrial error.

    It could also be that the attenuated form is not needed, part of the reason to use an attenuated form is that the pathogen will in possession of all it's http://en.wikipedia.org/wiki/Pathogen-associated_molecular_pattern" [Broken] because that may be all that is needed to grant a good immunity. Think of it this way, if you were showing me an enemy Knight I could learn a lot more from examining all the weaknesses in his armour as opposed to just examining his chest plate. Otherwise there's a chance that one day I face a group of knights who have bought (evolved) new chest plates without the weakness I'm familiar with.

    As for antibodies these are Y-shaped proteins also known as http://en.wikipedia.org/wiki/Antibody" [Broken] that are produced by the body's immune cells in response to a pathogen.
     
    Last edited by a moderator: May 5, 2017
  4. Jul 30, 2011 #3
    I think you meant antigens instead of antibodies.


    Attenuated vaccines are largely produced by repeatedly growing original strains of pathogens in a foreign host cell culture which are allowed to accumulate mutations. Therefore they lose their effectiveness in human tissue and are then administered as vaccines. However there is always a possibility of the strain's reversion to virulence i.e. after entering our bodies they may regain their virulence due to new mutations. This and the possibility of contamination of orignal culture like Ryan said, are some of the primary concerns associated with attenuated vaccines.
     
  5. Aug 4, 2011 #4
    Exactly, and it's always a risk vs benefit scenario. So when we look at what's required from the vaccine we can accomplish what's needed with least amount of risk.

    For instance with cholera it's mostly used for people traveling and in poorer countries. (AFAIK) Why put people at risk with the attenuated version if the inactive version provides moderate protection which will last more than long enough for the average 'trip'. This type of vaccination also works out well because it needs to be transported (most likely) to poorer nations. Attenuated vaccines require more advanced technology to regulate its environment, this isn't needed in inactive vaccines.

    Another major concern is for people with immunodeficiency. Whether this is due to disease or other medicines taken at the time of vaccination it is important that they do not take the attenuated virus. The attenuated virus is still living and able to reproduce. The only thing is though, that it reproduces slowly and it's viral efficiency is low enough that the average immune response can easily deal with it. But if we now have a person with very low immune response they may not be able to handle the vaccine and the probability of them getting sick as result is significantly higher.

    So as has already been stated, why put a patient at risk with a live virus/bacteria when they could easily just be treated with inactive virus/bacteria or even a fragment of that it. (as ryan mentioned).

    Attenuated vaccines are still preferred though due to the larger immune response, the patient needs to take only once and boosters are less frequent and the immunity is much more efficient due to the larger immune response. Sometimes though it's not necessary, or safe so instead the inactive vaccine is used.
     
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