I was under the impression that septicemia was the uncontrolled overgrowth of bacteria that enters the blood stream and that the immune system was not able to keep up with. If something successfully killed all the bacteria, then sepsis would be gone quickly.
Certainly there would be expected herxheimer but it actually would be less than if the infectious growth were to continue.
The body is going to have to clean and eliminate all of the microbes, toxins, and any other byproducts of the infection, so the faster you kill it, the faster that you stop it, the less herx that will be experienced. Just my experience.