Final answer:
Live attenuated vaccines stimulate a robust immune response by replicating in the host which can provide rapid and long-lasting immunity, usually with just a single dose. There is a risk of the weakened virus reverting to a pathogenic state through back mutations. The option (A) is correct.
Step-by-step explanation:
Because organisms in live attenuated vaccines replicate in the host, they stimulate an immune response that more closely mimics protection from natural infection. These vaccines can potentially lead to a more rapid onset of immunity and may require only a single dose to provide protection, in the absence of maternal-derived antibodies (MDA).
Live attenuated vaccines work by weakening the "wild-type" virus, using methods such as long-term culturing in an unnatural host or environment, which induces mutations that decrease the virus's ability to cause disease. This form of vaccination activates both cellular and humoral immunity and stimulates the development of memory for long-lasting immunity. However, there is a low but significant risk that these weakened viruses could revert to their disease-causing form through back mutations. Therefore, option (A) is correct.
This question is not complete, Here I am attaching the complete question:
Because organisms in _____________ vaccines replicate in the host, they stimulate an immune response that more closely mimics protection from natural infection. There is generally a more rapid onset of immunity than with inactivated vaccines, and, in the absence of MDA, only one dose of vaccine may be sufficient to provide protection.
A. Live attenuated
B. Inactivated
C. Toxoid
D. Subunit