An protein in the blood that is made by the body to fight germs such as viruses or bacteria. Antibodies can be a result of receiving a vaccine or coming into contact with a virus. They protect the body against future infections. An antibody is a protein in the blood that is made by the body to fight germs such as viruses or bacteria. Antibodies can be a result of receiving a vaccine or coming into contact with a virus. They protect the body against future infections.