How long do the biomeds (antibac, zeta-interferon, etc, pg. 135 Augmentation) remain active once you have taken them? Is this like a permanent inoculation thing or is just a temporary booster?

Based on the text from the Pharmaceuticals section (Augmentation 134), which the Biomeds fall under, I'd call it a temporary benefit. Also the Antibac description lists the immunity at 24 hours, and the Zeta-Interferon references the Antibac text.

Based on the idea that it only last 24 hours that makes AEXD stupidly expensive as you need to take it constantly to help prevent the onset of TLE-x. I know it says in Antibac it makes a character immune for 24 hours to a particular pathogen if taken before exposure and halves the power if taken after exposure. If it only lasts 24 hours then to get enough of this stuff to help you get over an infection of say Gamma-Anthrax you would need 5 days worth. Some of the other pathogens have an even longer duration, meaning even more of the drug. Seems weird a character can go in and get cyber or bioware installed in hours for very little but need to spend comparatively large sums to get over being infected with something and have a reasonable chance of living through it.

Bioweapons are a bitch, and bodmods are a consumer product.