title: Duration of antiviral immunity after smallpox vaccination.
abstract: Although naturally occurring smallpox was eliminated through the efforts of the World Health Organization Global Eradication Program, it remains possible that smallpox could be intentionally released. Here we examine the magnitude and duration of antiviral immunity induced by one or more smallpox vaccinations. We found that more than 90% of volunteers vaccinated 25-75 years ago still maintain substantial humoral or cellular immunity (or both) against vaccinia, the virus used to vaccinate against smallpox. Antiviral antibody responses remained stable between 1-75 years after vaccination, whereas antiviral T-cell responses declined slowly, with a half-life of 8-15 years. If these levels of immunity are considered to be at least partially protective, then the morbidity and mortality associated with an intentional smallpox outbreak would be substantially reduced because of pre-existing immunity in a large number of previously vaccinated individuals.
authors.affiliation: Oregon Health & Science University Vaccine and Gene Therapy Institute, 505 NW 185th Avenue, Beaverton, Oregon 97006, USA.
authors.forename: Erika
authors.initials: E
authors.lastname: Hammarlund
authors.forename: Matthew W
authors.initials: MW
authors.lastname: Lewis
authors.forename: Scott G
authors.initials: SG
authors.lastname: Hansen
authors.forename: Lisa I
authors.initials: LI
authors.lastname: Strelow
authors.forename: Jay A
authors.initials: JA
authors.lastname: Nelson
authors.forename: Gary J
authors.initials: GJ
authors.lastname: Sexton
authors.forename: Jon M
authors.initials: JM
authors.lastname: Hanifin
authors.forename: Mark K
authors.initials: MK
authors.lastname: Slifka
mesh_terms: D000328:Adult; D000368:Aged; D000917:Antibody Formation; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D003430:Cross-Sectional Studies; D005260:Female; D006207:Half-Life; D006801:Humans; D007117:Immunization, Secondary; D007156:Immunologic Memory; D008297:Male; D008875:Middle Aged; D012900:Smallpox Vaccine / Q000276:immunology* / Q000627:therapeutic use; D013601:T-Lymphocytes / Q000276:immunology* / Q000821:virology; D013997:Time Factors; D014616:Vaccinia virus / Q000276:immunology
chemical_list: D012900:Smallpox Vaccine