Transmission Reduction and Prevention With HPV Vaccination (TRAP-HPV) Study

Two prophylactic vaccines (Gardasil by Merck, and Cervarix by GlaxoSmithKline) have been proven in randomized controlled trials (RCT) to be highly effective in preventing infection against the target HPV types (HPV-6, 11, 16 and 18, for Gardasil, and HPV-16/18, for Cervarix) and the cervical precancerous lesions caused by them. These vaccines have shifted the paradigm of prevention and are expected to have a major impact in reducing the burden of cervical cancer and of other HPV-associated malignancies, such as vulvar, vaginal, penile, anal, and oropharyngeal cancers, as well as benign HPV-associated conditions (in the case of Gardasil), such as anogenital warts and respiratory papillomatosis. However, little is known about the extent with which vaccination may reduce transmission between sexual partners; i.e. much remains to be understood on the effects of HPV vaccine in preventing transmission of target HPV types to sexual partners of vaccinated individuals and its impact on herd immunity.

The investigators propose to conduct a placebo-controlled, double-blinded RCT to measure the impact of vaccination in preventing HPV transmission within young (age 18-45) heterosexual couples at McGill and Concordia Universities in Montreal, Canada. Individual partners in 500 couples* will be randomized to a treatment (Gardasil 9) or a control vaccine (Avaxim, a hepatitis A vaccine). This control vaccine provides a similar health benefit incentive as HPV vaccination while preserving the scientific cogency of a "placebo" comparator. Risk factor data will be collected via computerized questionnaires at enrolment (time 0), 2, 4, 6, 9 and 12 months*. At all time points, the investigators will measure HPV DNA infection status by polymerase chain reaction (PCR) in both partners in exfoliated penile, and oral samples from men and vaginal, oral samples from women. Assessing pre-enrolment humoral immune response to HPV infection with a competitive Luminex immunoassay (CLIA) will be done in an enrolment blood sample from all study participants.

The primary outcome will be the reduction of HPV DNA positivity for the target HPV vaccine types (types 6, 11, 16 and 18) in multiple anatomic sites in Avaxim-treated sexual partners of participants who received Gardasil 9. The investigators hypothesize that HPV vaccination is effective in reducing the risk of HPV transmission to their sexual partners. They will use the Kaplan-Meier technique and logrank tests to compare the cumulative probability of HPV infection in sexual partners of vaccinated versus unvaccinated individuals against follow-up time, and Cox proportional hazards regression to estimate the effect of vaccination and other covariates on transmission of HPV to sexual partners. Statistical analyses will follow an intention-to-treat approach but additional regression models will examine the role of several candidate determinants in mediating transmission and the protective effects. Mixed-effects models will also be used to take advantage of the repeated measurements across visits, HPV types, and anatomical sites for the same subject.

In addition to the findings on protection to unvaccinated partners, it is expected that this study will provide valuable insights as to whether protection may exist for a vaccine recipient in preventing infection in an anatomical site in which a target type has not yet established infection. These findings will generate key parameter data to inform the extent of herd immunity in cost-effectiveness models of HPV vaccination. Such models are essential to arrive at rational science-driven policies of HPV vaccination in girls and boys in Canada.

As of March 13, 2020, study visits were temporarily suspended due to the COVID-19 pandemic. With university approval, study visits were resumed as of May 26, 2020. Precautionary measures were put in place to minimize the risks related to exposure to the coronavirus. This included minimizing the number of participants present at the study site, using COVID-19 screening questionnaires prior to the visit, wearing personal protective equipment, disinfecting hands and common areas, and maintaining safe distancing. Transportation (by Taxi or Uber) or parking fees were also paid for to ensure safe distancing while traveling to the study site. The interruption in study visits due to the COVID-19 pandemic led to slight alterations in the timing of vaccinations, which will be adjusted for in the final analyses as required.

*With the slow accrual rates exacerbated by the COVID-19 pandemic, it was estimated that the target sample would not be reached within a reasonable timeframe. Therefore, we completed the study with 188 couples, before reaching the original target of 500 couples (1000 participants) and the interim target of 250 couples (500 participants) in order to maintain the scientific value of the study. In addition, we proposed to make the fifth time point the final visit. This shortened follow-up duration affected only three couples. Such protocol amendments were approved by the Institutional Review Boards.

Published protocol is available at PMID: 32788190