An observational study comparing HPV prevalence and type distribution between HPV-vaccinated and -unvaccinated girls after introduction of school-based HPV vaccination in Norway

Abstract

BackgroundMany countries have initiated school-based human papillomavirus (HPV) vaccination programs. The real-life effectiveness of HPV vaccines has become increasingly evident, especially among girls vaccinated before HPV exposure in countries with high vaccine uptake. In 2009, Norway initiated a school-based HPV vaccination program for 12-year-old girls using the quadrivalent HPV vaccine (Gardasil®), which targets HPV6, 11, 16, and 18. Here, we aim to assess type-specific vaginal and oral HPV prevalence in vaccinated compared with unvaccinated girls in the first birth cohort eligible for school-based vaccination (born in 1997).MethodsThis observational, cross-sectional study measured the HPV prevalence ratio (PR) between vaccinated and unvaccinated girls in Norway. Facebook advertisement was used to recruit participants and disseminate information about the study. Participants self-sampled vaginal and oral specimens using an Evalyn® Brush and a FLOQSwab™, respectively. Sexual behavior was ascertained through a short questionnaire.ResultsAmong the 312 participants, 239 (76.6%) had received at least one dose of HPV vaccine prior to sexual debut. 39.1% of vaginal samples were positive for any HPV type, with similar prevalence among vaccinated and unvaccinated girls (38.5% vs 41.1%, PR: 0.93, 95% confidence interval [CI]: 0.62–1.41). For vaccine-targeted types there was some evidence of lower prevalence in the vaccinated (0.4%) compared to the unvaccinated (6.8%) group (PR: 0.06, 95%CI: 0.01–0.52). This difference remained after adjusting for sexual behavior (PR: 0.04, 95%CI: 0.00–0.42). Only four oral samples were positive for any HPV type, and all of these participants had received at least one dose of HPV vaccine at least 1 year before oral sexual debut.ConclusionThere is evidence of a lower prevalence of vaccine-targeted HPV types in the vagina of vaccinated girls from the first birth cohort eligible for school-based HPV vaccination in Norway; this was not the case when considering all HPV types or types not included in the quadrivalent HPV vaccine.

The Effect of Prophylactic HPV Vaccines on Oral and Oropharyngeal HPV Infection—A Systematic Review

“…The literature search generated 1530 studies of which we included five cross-sectional studies [ 2 , 9 , 10 , 15 , 16 ], one randomized community trial study [ 17 ], one longitudinal cohort study [ 18 ] and two case-control studies [ 10 , 19 ], which in total encompasses 48,777 participants. A full overview of study characteristics can be found in Table 1 .…”

“…Four cross-sectional studies [ 2 , 10 , 15 , 16 ] observed a significant reduction in the presence of oral and oropharyngeal HPV infection after immunization with HPV vaccines. One cross-sectional study [ 9 ] proved inconclusive regarding vaccine effectiveness on oral and oropharyngeal HPV infection due to only four participants testing positive for any HPV type in oral samples, and was subsequently not included in the calculation of the mean RPP. The four cross-sectional studies had an RPP of 82.2% [ 2 ], 72.0% [ 10 ], 89.8% [ 15 ] and 91.7% [ 16 ], corresponding to a mean RPP of 83.9%.…”

“…One study [ 2 ] collected patient data from the National Health and Nutrition Examination Survey (NHANES), while others relied on self-reported vaccination status [ 10 , 15 , 16 ]. Biological material was collected in various ways; most studies relied on a swap-test from the oral cavity and tonsils [ 9 , 11 , 15 , 20 ]. Other studies used a gargle/rinse sample [ 2 , 10 ] while one study examined tissue from the tonsils of patients undergoing tonsillectomies [ 15 ].…”

“…One cross-sectional study [ 9 ] ( n = 312) found no correlation between HPV prevalence and vaccination status. The authors of this study claimed that results regarding oral and oropharyngeal infection proved inconclusive due to only four participants testing positive for any type of oral and oropharyngeal HPV infection.…”

“…The prevalence of oral and oropharyngeal HPV infections varies greatly amongst countries [ 2 , 9 , 10 ], and some studies, especially from Western countries, suggest that by the end of 2020, HPV will cause more oropharyngeal cancer than cervical cancer in high-resource countries [ 10 ]. The incidence of oropharyngeal cancer is much higher for males than for females [ 11 ].…”