What type of vaccine undergoes attenuation to create immunity without causing disease?

A live vaccine is designed to create immunity by using a weakened form of the pathogen that causes the disease. This process, known as attenuation, involves modifying the virus or bacteria so that it can still replicate and elicit an immune response without causing the disease in healthy individuals. By replicating within the host, these vaccines stimulate a strong and long-lasting immune response, often mimicking a natural infection.

In contrast, inactivated vaccines contain pathogens that have been killed or inactivated, which means they do not replicate and usually provide a shorter duration of immunity. Recombinant and subunit vaccines focus on specific components of the pathogen, such as proteins or genes, rather than using the whole pathogen, thereby not undergoing the attenuation process. Hence, live vaccines are unique in their ability to use an attenuated strain to generate a robust immune response while avoiding the actual disease.