title: Two-dose strategies for human papillomavirus vaccination: how well do they need to protect?
abstract: BACKGROUND
  Two-dose human papillomavirus (HPV) vaccine schedules may provide short-term protection but their long-term population impact is unknown.
  
  
  METHODS
  Two models of HPV transmission and associated cervical disease (squamous and glandular, neoplasia and cancer) were fitted to data from England and Canada on HPV epidemiology, sexual behaviour, cervical screening outcomes and cervical cancer incidence.
  
  
  RESULTS
  Models suggest that at 40-80% coverage, if two-dose schedules protect vaccinees for 20 years, then the benefits of the third dose are small. If two doses protect for 10 years, then the third dose may prevent as many cancers as the first two. At 80% coverage, numbers needed to receive a third dose to prevent an additional cancer are 5900-110,000 (England), 3000-5100 (Canada) with 20 years two-dose protection, and 2000-5300 (England), 760-950 (Canada) with 10 years two-dose protection.
  
  
  CONCLUSIONS
  Results enable decision makers to quantify risks associated with two-dose schedules despite remaining uncertainties in vaccine duration and cross-protection.
authors.affiliation: Modelling and Economics Unit, Public Health England, London NW9 5EQ, United Kingdom; Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, London WC1E 7HT, United Kingdom. Electronic address: mark.jit@phe.gov.uk.
authors.forename: Mark
authors.initials: M
authors.lastname: Jit
authors.affiliation: Modelling and Economics Unit, Public Health England, London NW9 5EQ, United Kingdom.
authors.forename: Yoon Hong
authors.initials: YH
authors.lastname: Choi
authors.affiliation: SP-POS, Centre de recherche du CHU de Québec, Québec, Canada.
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Laprise
authors.affiliation: Department of Infectious Disease Epidemiology, Imperial College, London W2 1PG, United Kingdom.
authors.forename: Marie-Claude
authors.initials: MC
authors.lastname: Boily
authors.affiliation: SP-POS, Centre de recherche du CHU de Québec, Québec, Canada; Département de médecine sociale et préventive, Université Laval, Québec City, QC G1V 0A6, Canada.
authors.forename: Mélanie
authors.initials: M
authors.lastname: Drolet
authors.affiliation: SP-POS, Centre de recherche du CHU de Québec, Québec, Canada; Department of Infectious Disease Epidemiology, Imperial College, London W2 1PG, United Kingdom; Département de médecine sociale et préventive, Université Laval, Québec City, QC G1V 0A6, Canada.
authors.forename: Marc
authors.initials: M
authors.lastname: Brisson
mesh_terms: D000293:Adolescent; D002170:Canada; D002648:Child; D004739:England; D005260:Female; D006801:Humans; D007117:Immunization, Secondary; D008954:Models, Biological; D030361:Papillomavirus Infections / Q000517:prevention & control*; D053918:Papillomavirus Vaccines / Q000008:administration & dosage*; D002577:Uterine Cervical Diseases / Q000517:prevention & control; D002583:Uterine Cervical Neoplasms / Q000517:prevention & control
chemical_list: D053918:Papillomavirus Vaccines
keywords: Cervical cancer; Human papillomavirus; Mathematical model; Vaccination