Viral integration of sequences into host and reassembly is possible.
Viral mutations, leaving the virus with the ability to enter and infect the cell either via ACE2 or cholesterol, will create a need for upgrading the vaccine eventually.
Current mRNA vaccines need multiple boosters, raising the point that these mRNA vaccines are inefficient.
Drift and shift will eventually require a modified vaccine in time.
Animal reservoirs, multiple simultaneous strains, will increase the likelihood of more mutant strains.
Treatment is the better option.
Treatment aimed at killing the virus without ramping up or immune system is the best way.
Using a treatment that modifies our immune system to kill the virus will lead to more problems.
Using medications to attack the virus at multiple points of its cycle is a much better technique.
Using a drug that does this (for instance ivermectin works at multiple aspects of the viral life cycle) or better yet a combination of drugs early on will help avoid resistance to certain meds in the long run.