Abstract 4680: Efficacy of the HPV16/18 vaccine against cervical, anal, and oral HPV infection among women with and without previous HPV16/18 exposure
Authors: Beachler Daniel C. , Kreimer Aimee R. , Schiffman Mark , Herrero Rolando , Wacholder Sholom , Rodriguez Ana Cecilia , Lowy Douglas R. , Porras Carolina , Schiller John T. , Jimenez Silvia , Struijk Linda , Schussler John , Hildesheim Allan , Gonzalez Paula ,   Costa Rica Vaccine Trial Group
Published: August 2015

Background: Previous reports from the Costa Rica Vaccine Trial demonstrated strong vaccine efficacy against HPV16/18 at the cervical, anal, and oral regions separately. However, the combined “woman-level” vaccine efficacy against infections at all three anatomic sites has not been examined in women with and without previous HPV16/18 exposure.

Methods: Women aged 18-25 from the Costa Rica Vaccine Trial were randomized to be vaccinated with the HPV16/18 Vaccine (Cervarix) or a Hepatitis A vaccine at enrollment. Cervical samples were collected at every annual visit, while oral and anal samples were collected only at the four year follow-up visit. Samples were tested for alpha mucosal HPV DNA types utilizing the SPF10 PCR-DEIA-LiPA25 version 1 method. An event in the multi-site woman-level vaccine efficacy analysis (n = 4,186) was defined as a women with prevalent HPV16/18 DNA at the cervical, anal, or oral regions. Vaccine efficacies (VEs) and 95% confidence intervals (95%CIs) were computed for one-time detection of HPV16/18 in the cervical, anal, and oral regions in this intention-to-treat analysis.

Results: Four years following initial vaccination, the combined multi-site woman-level vaccine efficacy against HPV16/18 infections was 64.8%, 95%CI = 54.8-72.8. Multi-site woman-level efficacy was stronger among women without evidence of previous HPV exposure (HPV16/18 seronegative and cervical HPV16/18 DNA negative at enrollment): VE = 83.1%, 95%CI = 72.6-89.6, but was also demonstrated among women with evidence of previous HPV16/18 exposure (HPV16/18 seropositive and cervical HPV16/18 DNA negative at baseline): VE = 49.6%, 95%CI = 2.7-73.9. Further supporting the partial protection of the vaccine in previously HPV16/18-exposed women, we observed a particularly strong vaccine efficacy against HPV16/18 at more than one anatomic site (VE = 91.4%, 95%CI = 81.4-96.6). Indeed, HPV16/18-infected women were significantly less likely to be HPV16/18-infected at two or more anatomic sites in the HPV vaccine arm than the control arm (6 of 81 (7%) vs. 70 of 230 (30%), p&lt;0.01).

Discussion: This is the first study to present a combined multi-site woman-level HPV16/18 vaccine efficacy. This study found strong multi-site efficacy among those not previously exposed to cervical HPV16/18, but also suggests the vaccine may provide some protection against HPV16/18 at multiple anatomic sites among women previously exposed to HPV16/18. If confirmed, the partial protection against cervical, anal, and/or oral HPV16/18 in women previously exposed to HPV16/18 could be considered in HPV vaccination catch-up program decision-making.

Citation Format: Daniel C. Beachler, Aimee R. Kreimer, Mark Schiffman, Rolando Herrero, Sholom Wacholder, Ana Cecilia Rodriguez, Douglas R. Lowy, Carolina Porras, John T. Schiller, Silvia Jimenez, Linda Struijk, John Schussler, Allan Hildesheim, Paula Gonzalez, Costa Rica Vaccine Trial Group. Efficacy of the HPV16/18 vaccine against cervical, anal, and oral HPV infection among women with and without previous HPV16/18 exposure. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4680. doi:10.1158/1538-7445.AM2015-4680