When scientists want to design a new vaccine against some disease they can use the old pathway: Use some weakened form of a pathogen to stimulate the body's immune system to recognize the agent as a threat, destroy it, and keep a memory of that pathogen, so that it can recognize and destroy it with much more efficiency if it encounters it in the future.
It works because some peptides of the surface of the pathogen are recognized by the immune system. Those peptides are called epitopes.
Nowadays, scientists prefer to design a vaccine by designing a peptide which is similar to a given epitope. The main roadblock is that different people have different immune system "sentinels". Some of those sentinels that patrol tissues are called MHC, they are proteins that have on one side receptors tailored to recognize a peptide decorating a pathogen, and on the other side they can activate T-cells (a subtype of blood's white cells).
It exists many services that help scientists to design peptides for a given MHC type, for example: http://www.cbs.dtu.dk/services/NetMHC/
However it is quite complex to use. One problem is that one must seed NetMHC with another peptide in order to receive the prediction from NetMHC. the choice of this peptide is not trivial.
A much simplified service, tailored for cancer vaccines and still relying on NetMHC 4 is available here:
PS: Indeed it is not enough to have this peptide to make a vaccine, one must add an adjuvant that will trigger the immune system, as the peptide most probably will be completely innocuous. The choice of the adjuvant and its administration is itself quite complex.
Another thing is that playing with the immune system is playing with fire. For example many recent drugs like check point inhibitors create auto-immune diseases like diabetes. Going from Charybdis to Scylla?