Which of the following best illustrates health maintenance medication?

Health maintenance medications are aimed at preventing disease and maintaining health rather than treating existing conditions. Vaccines are a perfect example of this because they work by stimulating the immune system to recognize and fight off specific pathogens, effectively preventing illness before it occurs. By providing immunity, vaccines play a crucial role in public health by reducing the incidence of infectious diseases.

The other options involve treatments or interventions that either address current health issues or are part of the diagnostic process. Antibiotics serve to treat existing bacterial infections, pain relievers are utilized during recovery to alleviate symptoms, and diagnostic tests are performed to identify health problems rather than maintain health. Thus, vaccines stand out as the option that embodies the principle of health maintenance through prevention.