What do you understand by the so called "human-first" or "Controlled Human Infection Model (CHIM)" approach in vaccine development? How it can make a difference in the efforts to tackle the menace of vector-borne diseases? Discuss.

Human-first or “Controlled Human Infection Model” is a trial method in vaccine development are intentionally challenged with disease organisms. The challenge organisms may range from wild pathogens, adopted or attenuated or genetically modified. The process involves trials on humans rather than animals in course of development of vaccines.
The “human-first” model offers various advantages such as:

• Current approach involves injecting animals with mild strain of parasites for drugs and vaccine development, only if it is found safe and effective, it is checked on humans. This results in wastage of money as many promising candidates may fail.
• Animal models are imprecise in reflecting diseases affecting humans.
• This model is being used to develop Thyroid vaccines in UK.

This model does present many challenges like:

1. Model cannot be used for all virulent especially those known for high fatality.
2. Only those strains can be used that induces an immune response and infection can be controlled by available medicines.

In case of vector borne diseases, strains are known and medicines are already present to deal with infection hence human first approach can be useful.
Thus human first model conducted with abundant caution and oversight with human volunteers completely aware of the risks and have given informed consent within ethical and regulatory framework can significantly reduce the vaccine introduction time.