You are incorrect. The rabies vaccine is the most effective prophylaxis against rabies. The post exposure protocol involves injecting immunoglobulin into the area around the wound, to bind to rabies virus in the vicinity of the wound, as well as administering the rabies vaccine (which is itself a protocol of multiple shots spaced out in time). It is the immunoglobulin which is the delaying treatment intended to give you more time for your immune system to develop its own antibodies against rabies virus after being stimulated by the vaccine.