Final answer:
The live attenuated vaccine from the list is VAR (Varicella vaccine). Live attenuated vaccines like VAR have a risk of reverting to virulence through back mutation but offer a strong immune response. Conjugate vaccines are used for certain pathogens with polysaccharide coatings to ensure immune recognition.
Step-by-step explanation:
The live attenuated vaccine in the list provided is VAR, which stands for the Varicella vaccine, commonly known as the chickenpox vaccine. Live attenuated vaccines are created by reducing the virulence of a pathogen without eliminating its ability to replicate. This process prompts the body to create an immune response capable of remembering and combating the pathogen in the future.
Risks associated with live attenuated vaccines include the slight but significant chance that the weakened pathogen can revert to a virulent form through back mutations. This can potentially lead to disease rather than immunity.
Conjugate vaccines are needed for pathogens with polysaccharide coatings like Haemophilus influenzae type B, because these coatings can disguise the pathogen's antigens to the immune system. Conjugating the polysaccharide to a protein, another type of antigen that the immune system responds to, ensures the immune system can recognize and respond to the pathogen.