Antibody
\æntɪˌbɑdi\
A large Y-shaped blood protein produced in response to and counteracting a specific antigen, such as bacteria and viruses. Determining whether someone has an antibody particular to a certain virus is done by a “serology test.” Determining what proportion of a population has antibodies to SARS-CoV-2 is important in separating the IFR from the CFR.
The objective of vaccination is to train the body to create antibodies using killed or weakened viruses.