Other

There are two broad approaches to infectious disease management:

• Prevention by vaccination (prophylactic)
  This utilises the immunological “memory” of a prior response to a particular antigen.  The key is to achieve memory without first incurring the full infection, through various approaches (eg killed pathogen, attenuated strain to not be virulent, sub-unit with antigen sets)  Though this clearly does not prevent subsequent contact with the pathogen, if this occurs, the body is able to mount a rapid cellular response to contain and rapidly eliminate the infection.

• Treatment by drug therapy
  In some cases, diseases are either adequately prevented or treated by therapeutic agents, though as pathogens continually evolve, there is a concern that resistance may emerge, eroding or negating current products’ efficacy.

The major unmet needs are in circumstances where neither acceptable therapeutic agents nor vaccination are available.

• Drug therapy is usually initiated once symptoms of infection have occurred, hence the patient is already suffering the consequences of infection.  At this stage of infection, therapy does little to halt the onward transmission of the disease.  Where drugs are available, they often lead to the development of resistant strains, as well as undesirable side effects.  For viral infection, where the pathogen invades cells, eradication is usually impossible and at best, drugs only contain progression.
• Vaccines are only available for a few pathogens.  They challenge the body with a low level of a pathogen, eliciting an immune response, but without triggering major infection.  Current vaccine technology seeks to modify the pathogen such that it is no longer disease-causing, while still inducing immunity.
  
  This is achieved by:
• Attenuation of the pathogen (altering the pathogen to render it harmless).
• Vaccination with killed pathogen (hence no risk from live pathogen).
• Subdivision of the pathogen (hence vaccinating with only a part of the pathogen).

However, each of these methods has major drawbacks: attenuated vaccines may revert to the harmful type (eg polio) or may be destroyed by an existing immune response before inducing immunity (eg BCG).  Killed or subunit vaccines are unable to induce protective immune responses without the use of Adjuvants and the safety risks of these non-specific immune stimulants pose severe limits to their utility.