Vaccines are biological medicines with the aim of preventing one or more infectious diseases by stimulating the immune system (production of antibodies, activation of specific cells) and thus acquiring so-called 'active immunity'. 

The "active substances" of vaccines are: micro-organisms (bacteria or viruses) that are suitably inactivated or killed in such a way as to stimulate the immune system without causing disease; specific parts (antigens) of the micro-organisms that are directly involved in the immune system's response to the specific pathogen; substances produced by the micro-organism itself (toxins) and involved in the mechanism by which that pathogen causes disease, made safe and effective through the vaccine production process. For information on schedules and bookings, contact the Prevention Department of the competent ASL.