Attenuated Vaccines Have Several Advantages

Attenuated vaccines have several advantages. Which of the following is NOT an advantage of these vaccines?

A) One or two doses of an attenuated agent are often enough to induce relatively long-lasting immunity.
B) Attenuated vaccines are very stable in all temperatures, so are easily transported to remote areas and do not require special storage.
C) The vaccine strain may be spread from the person being immunized to other non-immune people, thereby immunizing the contacts of the vaccine recipient.
D) Attenuated vaccines can sometimes be delivered orally or nasally, preventing the need for using syringes.
E) Attenuated vaccines cause a very strong cell-mediated immune response.