What significant breakthrough in medicine happened in 1928?

The discovery of penicillin in 1928 by Alexander Fleming marked a groundbreaking advancement in medicine, particularly in the field of antibiotics. Before this discovery, the treatment of bacterial infections was limited and often ineffective, leading to high mortality rates from what were once considered minor infections.

Fleming observed that the mold Penicillium notatum released a substance that killed a variety of bacteria, which led to the development of penicillin as a drug. This not only transformed the treatment of infections but also paved the way for the development of more antibiotics in subsequent decades. As a result, penicillin is often regarded as one of the most important medical breakthroughs of the 20th century, fundamentally changing how doctors approached bacterial illnesses and saving countless lives.

In contrast, the other options represent significant medical developments, but they occurred at different times or pertain to different areas of medicine. Anesthesia was developed in the mid-19th century; the smallpox vaccine was created by Edward Jenner in 1796, and antiseptic surgery was introduced by Joseph Lister in the 1860s. While these advancements were crucial, they do not relate to the specific breakthrough regarding penicillin in 1928.