A prophylactic is an advance intervention that prevents or mitigates the severity of disease. Vaccines in general, and all COVID vaccines, are prophylactics. Vaccines could be cures as well, but COVID vaccines are not.
Sufficient distribution of prophylactics for infectious disease can achieve eradication which, while distinct from a cure, is as good or better, but COVID vaccines haven't done that.
You seem to be confusing treatments with vaccines by lumping them under the same broad definition. A vaccine must be taken prior to contracting the disease, and will not work if taken after. This is exactly how COVID vaccines behave, therefore they are vaccines.
Now whether a vaccine is effective or not is a separate, almost orthogonal, dimension for consideration. No single vaccine is 100% effective, so we will always have certain % of cases where vaccines did not prevent the spread of infection and resulting adverse outcomes.
Sufficient distribution of prophylactics for infectious disease can achieve eradication which, while distinct from a cure, is as good or better, but COVID vaccines haven't done that.