Inactivated vaccines are made from viruses or bacteria that have been killed or inactivated so they can no longer cause disease. These vaccines stimulate the immune system to recognize and fight the pathogen without risking infection. Common examples include vaccines for polio and hepatitis A. These vaccines typically require multiple doses to achieve full immunity, as the immune response may be weaker compared to live vaccines. Inactivated vaccines are generally considered safe and can be used in individuals with weakened immune systems, making them an important tool in public health for preventing infectious diseases.