Vaccines and Drug Therapies

MEND is pursuing programs to make advancements in both vaccines and drugs for diseases of poverty. Though as noted above, the mechanisms of action of each are typically quite different, there is no doubt that both classes of medicine can benefit significantly from the application of advanced delivery technologies.

The table below contrasts some of the most common distinctions between vaccines and drugs:

	Vaccine	Drug
Purpose	Incite the immune system of a patient (without the disease) to recognize a harmless version of the infection, and therefore "prime" the patient to be able to effectively combat disease should exposure to the infectious agent occur. Immune responses can either occur at the humoral level (e.g. blood plasma & antibodies) or cell mediated (T-cells), or both.	Treat and eradicate (or control) active disease from an infected individual.
Composition	Most always a biologic organism: can be an antigen, a sub-unit protein that mimics the antigen’s receptors, an attenuated form of the infectious organism, a metabolically-active, non-replicating form, a related form that infects a different species, or other form.	Usually a chemically-synthesized "small" molecule which may not exist naturally.
Dosing	Single dose to stimulate or “prime” immune system. Thereafter, occasional doses as necessary to “boost” the immune system.	Dosing as necessary to maintain a “minimum inhibitory concentration” to either kill or prevent infectious organisms from replicating. In the case of TB, the dosing regimen can last 6 months.
Challenges	Since most vaccine candidates are biological large molecules, their stability is generally very difficult to maintain, requiring most vaccines to remain in suspension and refrigeration until the point of administration (which is most frequently injection). The ability to administer a vaccine and obtain efficacious and lasting immune system protection is a very complex process. The human body reacts very differently depending on whether an antigen (vaccine) is presented to mucosal surfaces (e.g. nasal, pulmonary, rectal) versus systemic administration (e.g. the bloodstream).	Drug resistance is a significant issue in all three primary diseases of poverty and growing. Co-morbidity of multiple diseases (in particular HIV and TB) create situations in which the standard treatment regimens for one disease alone cannot be followed. Drug regimens in TB are extremely long (6-9 months) and must be shortened to improve compliance. Drug regimens in HIV, while effective, are not curative.