Which of the following vaccines contains a live virus?

The correct choice is Varicella. This vaccine, which protects against chickenpox, contains a live attenuated virus. Live attenuated vaccines use a weakened form of the germ that causes a disease, which helps the immune system recognize and respond to the actual virus if encountered in the future.

In contrast, IPV (Inactivated Poliovirus Vaccine) contains killed poliovirus and does not stimulate an immune response through a live virus. DTaP, which protects against diphtheria, tetanus, and pertussis, is an inactivated vaccine that also does not contain live viruses. Similarly, the Hepatitis B vaccine is a recombinant vaccine made from a part of the hepatitis B virus and doesn't use live viral particles. Thus, Varicella is distinct among the options as it is the only vaccine listed that contains a live attenuated virus.