A- One dose of MMR vaccine is 93% effective against measles, 78% effective against mumps, and 97% effective against rubella. MMR is an attenuated (weakened) live virus vaccine.
B- Vivotif (Typhoid Vaccine Live Oral Ty21a) is a live attenuated vaccine for oral administration only. The vaccine contains the attenuated strain Salmonella typhi.
C- The smallpox vaccine protects people from smallpox by helping their bodies develop immunity to smallpox. The vaccine is made from a virus called vaccinia.
D- One approach is to develop a vaccine to prevent this deadly disease. Clinical studies indicate that mucosal immunity may provide some protection against recurrent intestinal infection with E. histolytica, but there is no clear evidence that protective immunity develops after amoebic liver abscess.
So, the correct option is 'Option D'.