Vaccines help so many ppl and before we had vaccines so many ppl died. The virus can evolve and can change and that why sometimes one vaccine doesn't work on specific virus.
Each vaccine work on different strain of virus (or combination of strains) and if there is a new strain out there it won't be affected by the vaccine.
It also can helps our immune system.
It is not black and white- you can give your body a chance against Flo virus, but not against papiloma (might get cancer from it)