The primary function of vaccines is to stimulate the immune system to recognize and fight specific pathogens. By introducing a harmless component or a weakened/inactivated form of the pathogen, vaccines prepare the immune system to respond quickly upon future exposures. This preemptive action helps prevent infectious diseases and has been crucial in controlling or eradicating many illnesses. Vaccination programs are vital public health tools that contribute to herd immunity and the overall health of populations.