What is an example of a live attenuated vaccine?

A live attenuated vaccine is one that contains a live but weakened form of the virus or bacterium that causes a particular disease. This type of vaccine works by stimulating a strong immune response without causing the disease in healthy individuals. The measles, mumps, and rubella (MMR) vaccine is a prime example of a live attenuated vaccine. It contains weakened forms of the viruses that cause measles, mumps, and rubella, allowing the immune system to recognize and fight these pathogens effectively if exposed in the future.

In contrast, the other vaccines mentioned are not classified as live attenuated. The inactivated polio vaccine contains killed virus particles, which is a different method and does not use a live pathogen. The tetanus toxoid vaccine is made from a toxin produced by the bacterium, which is inactivated to build immunity. Similarly, the hepatitis A vaccine is also an inactivated vaccine that contains killed virus particles. These different methodologies illustrate why the MMR vaccine stands out as a live attenuated option.