title: Proof-of-principle evaluation of the efficacy of fewer than three doses of a bivalent HPV16/18 vaccine.
abstract: BACKGROUND
  Three-dose regimens for human papillomavirus (HPV) vaccines are expensive and difficult to complete, especially in settings where the need for cervical cancer prevention is greatest.
  
  
  METHODS
  We evaluated the vaccine efficacy of fewer than three doses of the HPV16/18 vaccine Cervarix in our Costa Rica Vaccine Trial. Women were randomly assigned to receive three doses of the HPV16/18 vaccine or to a control vaccine and were followed for incident HPV16 or HPV18 infection that persisted in visits that were 10 or more months apart (median follow-up 4.2 years). After excluding women who had no follow-up or who were HPV16 and HPV18 DNA positive at enrollment, 5967 women received three vaccine doses (2957 HPV vaccine vs 3010 control vaccine), 802 received two doses (422 HPV vs. 380 control), and 384 received one dose (196 HPV vs. 188 control). Reasons for receiving fewer doses and other pre- and post-randomization characteristics were balanced within each dosage group between women receiving the HPV and control vaccines.
  
  
  RESULTS
  Incident HPV16 or HPV18 infections that persisted for 1 year were unrelated to dosage of the control vaccine. Vaccine efficacy was 80.9% for three doses of the HPV vaccine (95% confidence interval [CI] = 71.1% to 87.7%; 25 and 133 events in the HPV and control arms, respectively), 84.1% for two doses (95% CI = 50.2% to 96.3%; 3 and 17 events), and 100% for one dose (95% CI = 66.5% to 100%; 0 and 10 events).
  
  
  CONCLUSIONS
  Four years after vaccination of women who appeared to be uninfected, this nonrandomized analysis suggests that two doses of the HPV16/18 vaccine, and maybe even one dose, are as protective as three doses.
authors: Infections and Immunoepidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, 6120 Executive Blvd, EPS/7084, Rockville, MD 20852, USA. kreimera@mail.nih.gov
authors: Aimée R
authors: AR
authors: Kreimer
authors: Ana Cecilia
authors: AC
authors: Rodriguez
authors: Allan
authors: A
authors: Hildesheim
authors: Rolando
authors: R
authors: Herrero
authors: Carolina
authors: C
authors: Porras
authors: Mark
authors: M
authors: Schiffman
authors: Paula
authors: P
authors: González
authors: Diane
authors: D
authors: Solomon
authors: Silvia
authors: S
authors: Jiménez
authors: John T
authors: JT
authors: Schiller
authors: Douglas R
authors: DR
authors: Lowy
authors: Wim
authors: W
authors: Quint
authors: Mark E
authors: ME
authors: Sherman
authors: John
authors: J
authors: Schussler
authors: Sholom
authors: S
authors: Wacholder
mesh_terms: D000293:Adolescent; D000328:Adult; D052685:Alphapapillomavirus / Q000276:immunology*; D000914:Antibodies, Viral / Q000097:blood; D003364:Costa Rica / Q000453:epidemiology; D004305:Dose-Response Relationship, Drug; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D030361:Papillomavirus Infections / Q000453:epidemiology / Q000517:prevention & control* / Q000821:virology; D053918:Papillomavirus Vaccines / Q000008:administration & dosage*; D012107:Research Design; D016896:Treatment Outcome; D014412:Tumor Virus Infections / Q000453:epidemiology / Q000517:prevention & control* / Q000821:virology; D002583:Uterine Cervical Neoplasms / Q000453:epidemiology / Q000517:prevention & control* / Q000821:virology*; D055815:Young Adult
chemical_list: D000914:Antibodies, Viral; D053918:Papillomavirus Vaccines; C510352:human papillomavirus vaccine, L1 type 16, 18