>>11537639First you got to isolate whatever part of the virus that activates antibody response from the immune system. Here you have to be careful it doesn't also activates against healthy cells or you get fucked.
Second you have to work out on a delivery system that do not fuck up the payload while also is easy to mass produce and store with the longest shelf life possible.
Third you have to work out the appropriate quantity to be delivered to produce enough antibodies to kill the disease once you are exposed to it and work out how long is the effect.
The third part takes the longer because you have actually test with animals then human for a huge range of doses and the wait a few months to see what did work.