Immunity is indicated by the presence of [[antibodies]] in the blood and can usually be determined with a laboratory test.<ref>https://www.cdc.gov/vaccines/about/terms/glossary.htm#i</ref> | Immunity is indicated by the presence of [[antibodies]] in the blood and can usually be determined with a laboratory test.<ref>https://www.cdc.gov/vaccines/about/terms/glossary.htm#i</ref> |