Long‐term follow‐up of human papillomavirus type replacement among young pregnant Finnish females before and after a community‐randomised HPV vaccination trial with moderate coverage

Abstract

Large scale human papillomavirus (HPV) vaccination against the most oncogenic high-risk human papillomavirus (HPV) types 16/18 is rapidly reducing their incidence. However, attempts at assessing if this leads to an increase of nonvaccine targeted HPV types have been hampered by several limitations, such as the inability to differentiate secular trends. We performed a population-based serological survey of unvaccinated young women over 12 years. The women were under 23-years-old, residents from 33 communities which participated in a community-randomised trial (CRT) with approximately 50% vaccination coverage. Serum samples were retrieved pre-CRT and post-CRT implementation. Seropositivity to 17 HPV types was assessed. HPV seroprevalence ratios (PR) comparing the postvaccination to prevaccination era were estimated by trial arm. This was also assessed among the sexual risk-taking core group, where type replacement may occur more rapidly. In total, 8022 serum samples from the population-based Finnish Maternity Cohort were retrieved. HPV types 16/

HPV cervical infections and serological status in vaccinated and unvaccinated women

“…Indeed, since the vaccines target a limited number of genotypes, it is theoretically possible that non-vaccine genotypes may rise in prevalence occupying the niche vacated by genotypes targeted by the vaccine, either directly or indirectly due to cross-protective eects. Though technically a challenge [27,28], it is important in the post-vaccination era that studies continue to track genotype specic prevalences [29], especially given that current vaccination programs do not cover all oncogenic HPV genotypes.…”

HPV cervical infections and serological status in vaccinated and unvaccinated women

“…Indeed, since the vaccines target a limited number of genotypes, it is theoretically possible that non-vaccine genotypes may rise in prevalence occupying the niche vacated by genotypes targeted by the vaccine, either directly or indirectly due to cross-protective effects. Though technically a challenge [27, 28], it is important in the post-vaccination era that studies continue to track genotype specific prevalences [29], especially given that current vaccination programs do not cover all oncogenic HPV genotypes.…”

Human papillomavirus seroprevalence in pregnant women following gender-neutral and girls-only vaccination programs in Finland: A cross-sectional cohort analysis following a cluster randomized trial

“…described as the natural counterpart to the serology-based type-replacement study concerning non-vaccine HPV types [18].…”

“…The 1992 to 1995 birth cohorts were exposed to community-level vaccination via the community-randomized trial intervention, and the 1998 and younger birth cohorts were exposed to community-level HPV vaccination via the Finnish national HPV vaccination program initiated in late 2013 (Fig 1 Data regarding self-reported maternal smoking among women under the age of 23 years and resident in the 33 communities between 2005 and 2016 were collected from the Finnish Medical Birth Register, and used as a surrogate of community-level risk-taking behaviors. To define the core group with high contact rate, we identified herpes simplex virus type 2 (HSV-2) seropositive women [18]. Data on community-specific vaccination coverage over each calendar year were collected from the HPV trial registry for the birth cohorts exposed to the community-randomized trial and from the Finnish vaccination register for the birth cohorts exposed to the Finnish national HPV vaccination program.…”

“…We performed population-based HPV analysis to evaluate the herd effect created by gender-neutral or girls-only vaccination following our community-randomized trial in the instance of low to moderate vaccination coverage. In the previous reports of this trial, the herd effect was evaluated using transitory HPV PCR positivity in study participants when they were aged 18 and/or 22 years; although notable HPV18 herd effect was observed, no HPV16 herd effect was found [ 12 , 13 , 18 ]. To provide assurance that the lack of HPV16 herd effect was not due to the methodological approach, we then nested a cross-sectional cohort within the community-randomized trial.…”