HPV Vaccines—Prophylactic, Not Therapeutic

Two human papillomavirus (HPV) L1 viruslike particle (VLP) vaccines have been developed against HPV types 16 and 18—the 2 HPV types that account for about 70% of cervical cancers worldwide.¹ Both vaccines have been found to have high prophylactic efficacy in large clinical trials.^2- 6

In this issue of JAMA, Hildesheim and colleagues⁷ report the effect of vaccination with one of these vaccines, the bivalent HPV-16/18 vaccine, on viral clearance. These results are from an ongoing community-based trial of more than 7000 18- to 25-year-old women in Costa Rica. The main analysis of the ongoing trial, as for other recently published trials of HPV vaccines,^2- 5 will focus on vaccine efficacy among women not infected with the specific HPV vaccine types at the time of enrollment. In contrast, the analysis by Hildesheim et al addresses the question of whether the vaccine can clear HPV type 16/18 infection present at the time of vaccination. The results demonstrate no effect of the vaccine on viral clearance. Among women who had HPV-16 or HPV-18 infection at enrollment, defined as HPV DNA detected in a cervical specimen, vaccine efficacy for preventing persistent infection with HPV-16, HPV-18, or both at 6 months was 2.5% (95% confidence interval [CI], −9.8% to 13.5%) and at 12 months was −2.0% (95% CI, −24.3% to 16.3%).