Potential impact of switching from a two- to one-dose gender-neutral routine HPV vaccination program in Canada: A mathematical modeling analysis

ABSTRACT Background Worldwide, countries are examining whether to implement one-dose HPV vaccination. To inform policy recommendations in Canada, we used mathematical modeling to project the population-level impact and efficiency of switching from two-to one-dose gender-neutral routine HPV vaccination. Methods We used HPV-ADVISE, an individual-based transmission-dynamic model of HPV infections/diseases, to model 2 provinces (Quebec, Ontario), which represent higher (≈85%) and lower (≈65%) HPV vaccination coverage in Canada. We examined non-inferior and pessimistic scenarios of one-dose efficacy (VE=98%, 90%) and average duration (VD=lifelong, 30 years, 25 years) versus two doses (VE=98%, VD=lifelong). Our main outcomes were the relative reduction in HPV-16 (among females/males) and cervical cancers, and the number of doses needed to prevent one cervical cancer (NNV). Results Our model projects that one-dose HPV vaccination would avert a similar number of cervical cancers as two doses in Canada, under various non-inferior and pessimistic scenarios. Under the most pessimistic scenario (VD=25 years), one-dose vaccination would avert ∼3 percentage-points fewer cervical cancers than two doses over 100 years. All one-dose scenarios were projected to lead to cervical cancer elimination and were projected to be a substantially more efficient use of vaccine doses compared to two doses (NNVs one-dose vs no vaccination=800-1000; incremental NNVs two-dose vs one-dose vaccination >10,000). Interpretation If the average duration of one-dose protection is longer than 25 years, individuals would be protected during their peak ages of sexual activity and one-dose vaccination would prevent a similar number of HPV-related cancers, while being a more efficient use of vaccine doses.