Vaccines are for preventing the disease. Even for rabies, if you get it after the symptoms begin, it's too late.

> A vaccine is a biological preparation that provides active acquired immunity to a particular infectious or malignant disease.

While most are prophylactic, it's not a requirement to be considered a vaccine. Vaccines are not "meant to prevent a disease". They're meant to provide immunity to the disease, whether that be before (prophylactic/prevention) or during (therapeutic/treatment).

Web search for "therapeutic vaccines." You're missing about half the picture.

You are conflating your personal definition with the medical world's.

But before symptoms you still have it so it's not only for preventing disease.

Vaccines are used to teach/modify your immune system to fight something. Whether you have it or not is not part of the definition[0].

[0] a substance used to stimulate the production of antibodies and provide immunity against one or several diseases, prepared from the causative agent of a disease, its products, or a synthetic substitute, treated to act as an antigen without inducing the disease.