what determines what kind of vaccine is used?

such as live attenuated or inactivated etc
Answers:
It depends to a certain extent on the characteristics of the organism that you are trying to protect against. Many bacteria maintain a relatively "constant" external appearance biochemically, so it is often possible to direct an antibody against a static surface protein with good results. Many viruses pose different problems, and not simply due to rates of mutation (such as with the flu). Some live virus (attentuated) vaccines are needed to sustain or even mount an effective immune response to begin with because of the tendency of the virus to escape robust immune initiation.

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A live attenuated vaccine contains a virus that is "live" but it does not create any pathogenic effect. That is the virus can replicates in the cells but it does not create any pathogenic effect. An inactivated vaccine or a killed vaccine contains either virion particles, viruses killed by formalin or toxoids (inactivated toxins) such as diptheria and tetanus. Both vaccines ellicit an immune response both T-cells and b cells. But a live attenuated virus has a longer lasting immunity. This is because it has a live virus that is simiar to the wild type. However this is dangerous because the virus can revert back to the wild type and cause disease. This is the case for the oral polio (sabin) vaccine as there are poliomyelitis caused by vaccination. The live vaccinia virus was given for smallpox immunisation. Basically this type of vaccines immunises a large group of people because the live virus from the vaccine can be spread from the immunised person. This is known as herd immunity. However this is not good in cases whereby the person is immunocompromised for pregnant.A killed vaccine has a shorter immunity and requires booster doses. However the virus does not revert back to become pathogenic and is relatively safe to use. This is used for immunising small groups of people individually as the virus cannot be spread. Toxoid vaccines do not have the bacteria that produces the toxins, only the inactivated toxins. This is to elicit an antibody production so that when the person is infected by a real toxin, the antibodies binds to and inactivates the toxins.Hope this helps.

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