Context: Viruslike particle human papillomavirus (HPV) vaccines were designed to prevent HPV infection and development of cervical precancers and cancer. Women with oncogenic HPV infections might consider vaccination as therapy.
Objective: To determine whether vaccination against HPV types 16 and 18 increases the rate of viral clearance in women already infected with HPV.
Design and setting: Phase 3, masked, community-based randomized trial conducted in 2 provinces of Costa Rica.
Participants: A total of 2189 women aged 18 to 25 years who were recruited between June 2004 and December 2005. Participants were positive for HPV DNA at enrollment, had at least 6 months of follow-up, and had follow-up HPV DNA results.
Intervention: Participants were randomly assigned to receive 3 doses of a bivalent HPV-16/18 L1 protein viruslike particle AS04 candidate vaccine (n = 1088) or a control hepatitis A vaccine (n = 1101) over 6 months.
Main outcome measures: Presence of HPV DNA was determined in cervical specimins by a molecular hybridization assay using chemiluminescence with HPV RNA probes and by polymerase chain reaction using SPF10 primers and a line probe assay detection system before vaccination and by polymerase chain reaction after vaccination. We compared rates of type-specific viral clearance using generalized estimating equations methods at the 6-month visit (after 2 doses) and 12-month visit (after 3 doses) in the 2 study groups.
Results: There was no evidence of increased viral clearance at 6 or 12 months in the group who received HPV vaccine compared with the control group. Clearance rates for HPV-16/18 infections at 6 months were 33.4% (82/248) in the HPV vaccine group and 31.6% (95/298) in the control group (vaccine efficacy for viral clearance, 2.5%; 95% confidence interval, -9.8% to 13.5%). Human papillomavirus 16/18 clearance rates at 12 months were 48.8% (86/177) in the HPV vaccine group and 49.8% (110/220) in the control group (vaccine efficacy for viral clearance, -2.0%; 95% confidence interval, -24.3% to 16.3%). There was no evidence of a therapeutic effect for other oncogenic or nononcogenic HPV categories, among women receiving all vaccine doses, among women with single infections, or among women stratified by the following entry variables: HPV-16/18 serology, cytologic results, HPV DNA viral load, time since sexual debut, Chlamydia trachomatis or Neisseria gonorrhoeae infection, hormonal contraceptive use, or smoking.
Conclusion: In women positive for HPV DNA, HPV-16/18 vaccination does not accelerate clearance of the virus and should not be used to treat prevalent infections.
Trial registration: clinicaltrials.gov Identifier: NCT00128661.