A vaccine essentially simulates an infection so that our body produces antibodies against it & thus helps when we actually get infected in the future.
But for some diseases, we see post exposure vaccination - for e.g. Tetanus & Rabies.
How can this work? If the pathogen is already in our body, then our immune system would produce antibodies against it just like it would against the vaccine. So what is the point.
I found this paper which is an attempt.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7159179/
They say this for tetanus
However, postexposure vaccination against tetanus produces an adequate amount of antitoxin in just 4–7 days, leaving a small window for a postexposure vaccine to outpace the natural, 10-day incubation
However, this explanation doesn't make sense to me consider what incubation period means
https://en.wikipedia.org/wiki/Incubation_period
Incubation period (also known as the latent period or latency period) is the time elapsed between exposure to a pathogenic organism, a chemical, or radiation, and when symptoms and signs are first apparent. In a typical infectious disease, the incubation period signifies the period taken by the multiplying organism to reach a threshold necessary to produce symptoms in the host.
Is the number of viruses delivered by a vaccine higher the number of viruses it would replicate into in an actual infection by the end of the incubation period? I couldn't find any place - the number of actual live/attenuated/dead viruses delivered by a vaccine.
And this is explanation is given in the link only for tetanus, they say they don't understand why or how post-exposure vaccination works for Rabies.
I understand that the Rabies virus is a stealth virus. The body/immune system can't detect it till it reaches the brain. So is this changed in the rabies vaccine? Does the body/immune system detect the Rabies virus delivered by the vaccine - if yes, what change has been done in the virus so that it is no longer a stealth virus?
Have there been trials done where they tried only immunoglobin or only vaccine to see if both are required & if yes, which has a bigger effect - the vaccine or the immunoglobin?
