Describe a medical advance that has led to a decrease in the spread of communicable diseases. what is the advance? how does it prevent the spread of disease?

Communicable Diseases are illnesses which are caused by pathogens or microorganisms, e.g virus and bacteria, that are transmitted from one person or animal to another in different ways. It can spread through contact of body fluids or blood, sexual contact, contaminated food and water, or through air.
With the advancement of medical science, different ways of controlling communicable diseases have emerged throughout the centuries and have been proven to lessen the mortality rate as time passed.
One is the development of Immunization. Immunization; to make one's body immune to a certain disease so it will be easier for the body to combat with the pathogens in contact with it. Until now, production of Immunization is still being updated depending upon the diseases that are currently affecting the majority. The development of immunization has given medical science, then and now, a very big impact in controlling diseases. How does it work? Immunization boosts the body's natural immunity whenever microorganisms enter the body. The body identifies these microorganisms as foreign elements, thus releasing certain kinds of cells to help fight off the infection.