||Rodríguez AC, Solomon D, Herrero R, Hildesheim A, González P, Wacholder S, Porras C, Jiménez S, Schiffman M, CVT Group, Alfaro M, Barrantes M, Bratti M, Cárdenas F, Cortés B, Espinoza A, Estrada Y, González P, Guillén D, Herrero R, Jiménez SE, Morales J, Villegas L, Morera LA, Pérez E, Porras C, Rodríguez AC, Rivas L, Freer E, Bonilla J, García-Piñeres A, Silva S, Atmella I, Ramírez M, Hildesheim A, Kreimer AR, Lowy DR, Macklin N, Schiffman M, Schiller JT, Sherman M, Solomon D, Wacholder S, Pinto L, Kemp T, Eklund C, Hutchinson M, Sidawy M, Quint W, van Doorn LJ
||The impact of human papillomavirus (HPV) vaccination on cervical screening, colposcopy, and treatment is incompletely understood. In 2004-2005, investigators in the Costa Rica Vaccine Trial randomized 7,466 women aged 18-25 years, 1:1, to receive HPV vaccination or hepatitis A vaccination. The worst-ever cytology diagnosis and the 4-year cumulative proportions of colposcopy referral and treatment by vaccination arm were compared for 2 cohorts. The total vaccinated cohort included 6,844 women who provided cervical samples. The naive cohort included 2,284 women with no evidence of previous HPV exposure. In the total vaccinated cohort, HPV-vaccinated women had a significant (P = 0.01) reduction in cytological abnormalities: 12.4% for high-grade lesions and 5.9% for minor lesions. Colposcopy referral was reduced by 7.9% (P = 0.03) and treatment by 11.3% (P = 0.24). Greater relative reductions in abnormal cytology (P < 0.001) were observed for HPV-vaccinated women in the naive cohort: 49.2% for high-grade lesions and 18.1% for minor lesions. Colposcopy referral and treatment were reduced by 21.3% (P = 0.01) and 45.6% (P = 0.08), respectively, in the naive cohort. The overall impact on health services will be modest in the first years after vaccine introduction among young adult women, even in regions with high coverage.