Which type of vaccines must replicate to stimulate an immune response?

Live attenuated vaccines are designed to contain a weakened form of the virus or bacteria that causes a disease. This means they can replicate in the body to a certain extent without causing the actual disease. The replication of these live attenuated organisms is a crucial aspect because it mimics a natural infection, which stimulates a robust and long-lasting immune response. This immune response includes the activation of T-cells and the production of antibodies.

In contrast, inactivated vaccines contain pathogens that have been killed or inactivated, meaning they cannot replicate. Subunit vaccines use pieces of the pathogen, such as proteins or sugars, to trigger an immune response, and they also do not replicate. Conjugate vaccines are formed by linking a poor antigen to a strong antigen to elicit a stronger immune response, but they too do not replicate. Therefore, live attenuated vaccines uniquely provide the replication feature essential for generating a strong and long-term immunity against infectious diseases.