Target groups for HPV vaccination are controversial. We evaluated vaccine efficacy (VE) against 1-year persistent infection, stratified by age and sexual behavior. We randomized 7,466 healthy women 18-25y to HPV16/18 or Hepatitis A vaccine (follow-up=50.4 months). According-to-protocol (ATP) cohorts included compliant HPV-negative women; intention-to-treat (ITT) included all randomized women. ATP VE was 90.9% (95%CI=82.0, 95.9) against HPV16/18 infections, 44.5% against HPV31/33/45 (95%CI=17.5, 63.1) and 12.4% (95% CI=-3.2, 25.6) against any oncogenic infection. Overall ITT VE against HPV16/18 infections was 49.0%, but ATP and ITT VE almost reached 100% in year 4 of follow-up. ATP efficacy against HPV16/18 was similar by age, but ITT VE was highest among youngest women (68.9% among 18-19; 21.8% among 24-25 years olds) and 79.8% among virgins. Among previously unexposed women, vaccination is highly efficacious against HPV16/18 and partially against HPV31/33/45. Vaccination is most effective before initiating sexual activity, with programmatic and individual decision implications.
- Received June 9, 2011.
- Revision received August 25, 2011.
- Accepted August 29, 2011.
- Copyright © 2011, American Association for Cancer Research.