The rabies vaccine is part of rabies treatment, but it's used in the window between being exposed to rabies and developing rabies. People who've been exposed but haven't been previously vaccinated also get Rabies Immune Globulin, which provides immediate antibodies until the body can respond to the vaccine by actively producing antibodies of its own.

CDC: "Rabies vaccine is given to people at high risk of rabies to protect them if they are exposed. It can also prevent the disease if it is given to a person after they have been exposed."[1]

[1] https://www.cdc.gov/vaccines/hcp/vis/vis-statements/rabies.h...

https://www.mayoclinic.org/diseases-conditions/rabies/diagno...

Maybe the vaccine can still stimulate you or immune system faster than the virus can take hold?