Final answer:
Vaccines aim to prevent disease spread, establish immunity, and reduce infection severity by stimulating the immune system to recognize and respond to pathogens. They have been crucial in eradicating and controlling diseases like smallpox, polio, and measles, saving millions of lives annually.
Step-by-step explanation:
The primary goals of vaccines are to prevent the spread of infectious diseases, to establish immunity without causing the actual disease, and to reduce the severity of infection if it occurs. Vaccines work by introducing weakened, killed, or parts of the pathogen into the body to stimulate the immune system to produce a response. The resulting immune memory allows the body to respond more efficiently to future exposures to the disease, thereby controlling and reducing symptoms as well as preventing the onset of the actual disease.
Vaccines have played a crucial role in eradicating smallpox and drastically reducing the incidence of diseases such as polio, measles, mumps, and rubella. Through widespread immunization, vaccines save millions of lives each year and dramatically decrease morbidity and mortality related to viral infections. The development and usage of vaccines are one of the most successful public health measures in preventing the spread of infectious diseases.