Vaccines are medical interventions designed to protect individuals from infectious diseases by triggering an immune response without causing illness. They can be developed using weakened or inactivated pathogens, or through newer technologies such as mRNA. Widely used in public health programs, vaccines have significantly reduced the prevalence of diseases like polio, measles, and influenza. Their development, distribution, and adoption are closely monitored by healthcare authorities and investors due to their impact on global health and pharmaceutical markets.