Contact patterns and HPV-genotype interactions yield heterogeneous HPV-vaccine impacts depending on sexual behaviours: an individual-based model

Human papillomaviruses are common sexually transmitted infections, caused by a large diversity of genotypes. In the context of vaccination against a subgroup of genotypes, better understanding the role of genotype interactions and human sexual behavior on genotype ecology is essential. Herein, we present an individual-based model that integrates realistic heterosexual partnership behaviors and simulates interactions between vaccine and non-vaccine genotypes. Genotype interactions were considered, assuming a previous vaccine-genotype infection shortened (competition) or extended (synergy) the duration of a secondary non-vaccine-genotype infection. Sexual behavior determined papillomavirus acquisition and transmission: only 19.5% of active individuals with 0–1 partner during the year, but >80% of those with ≥2 partners, were infected before vaccine introduction. Genotype interactions, despite being silent during the pre-vaccination era, markedly impacted genotype ecology after vaccination started, with a significant increase/decrease of non-vaccine prevalence for competitive/synergistic interactions. These changes were more pronounced in individuals with ≤3 partners (up to 30% of prevalence modification assuming 65% vaccine coverage) but barely visible for individuals with >3 partners (at most 0.30%). Results suggest that considering genotype interactions, in conjunction with heterogeneous sexual behaviors, is essential to anticipate the impact of existing and future anti-papillomavirus vaccines targeting a subgroup of genotypes.