How have antibiotics improved health?

Vaccines are the preventative measure. By inserting dead or weakened pathogens, or an artificial agent that resembles it, the immune system can learn to recognize it and destroy it before a real infection can occur. This reduces the number of carriers in a population. Antibiotics are used against bacterial infections already underway, and either kill or inhibit the growth of infections. Antibiotics must be taken as long as the doctor orders or lingering bacteria can develop a resistance to the drug.