Developing a new vaccine takes about 5-10 years. So how is it possible to develope Corona vaccine so quickly?

vaccines were designed by using new technologies (i.e., RNA-based vaccines and adenovirus-based vaccines)

Explanation:

RNA-based vaccines are vaccines based on the delivery of specific messenger RNA (mRNA) sequences that are capable of encoding only one viral protein, thereby preventing the complete viral cycle/replication. Subsequently, this protein is recognized by the immune system that generates memory immunity by synthesizing specific antibodies against this protein (in this case, the spike S protein). On the other hand, adenovirus-based vaccines are vaccines designed by inserting a transgene cassette into an adenovirus which is used as vector to produce one specific viral protein inside the host. Like mRNA vaccines, this antigenic viral protein is then recognized by the immune system in order to produce antibodies against a defined protein epitope, thereby producing memory immunity.

the answer is b. glad to .