Objective To assess the risk of serious adverse events after vaccination of adolescent girls with quadrivalent human papillomavirus (qHPV) vaccine.Design Register based cohort study. Setting Denmark and Sweden, October 2006 to December 2010.Participants 997 585 girls aged 10-17, among whom 296 826 received a total of 696 420 qHPV vaccine doses.Main outcome measures Incident hospital diagnosed autoimmune, neurological, and venous thromboembolic events (53 different outcomes) up to 180 days after each qHPV vaccine dose. Only events with at least five vaccine exposed cases were considered for further assessment. Rate ratios adjusted for age, country, calendar year, and parental country of birth, education, and socioeconomic status were estimated, comparing vaccinated and unvaccinated person time. For outcomes where the rate ratio was significantly increased, we regarded three criteria as signal strengthening: analysis based on 20 or more vaccine exposed cases (reliability), rate ratio 3.0 or more (strength), and significantly increased rate ratio in country specific analyses (consistency). We additionally assessed clustering of events in time and estimated rate ratios for a risk period that started on day 181.Results Among the 53 outcomes, at least five vaccine exposed cases occurred in 29 and these were analysed further. Whereas the rate ratios for 20 of 23 autoimmune events were not significantly increased, exposure to qHPV vaccine was significantly associated with Behcet's syndrome, Raynaud's disease, and type 1 diabetes. Each of these three outcomes fulfilled only one of three predefined signal strengthening criteria. Furthermore, the pattern of distribution in time after vaccination was random for all three and the rate ratios for these outcomes in the period from day 181 after vaccination were similar to the rate ratios in the primary risk period. The rate ratios for five neurological events were not significantly increased and there were inverse associations with epilepsy (rate ratio 0.66, 95% confidence interval 0.54 to 0.80) and paralysis (0.56, 0.35 to 0.90). There was no association between exposure to qHPV vaccine and venous thromboembolism (0.86, 0.55 to 1.36).Conclusions This large cohort study found no evidence supporting associations between exposure to qHPV vaccine and autoimmune, neurological, and venous thromboembolic adverse events. Although associations for three autoimmune events were initially observed, on further assessment these were weak and not temporally related to vaccine exposure. Furthermore, the findings need to be interpreted considering the multiple outcomes assessed.

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Human papillomavirus (HPV) types 16/18, included in HPV vaccines, contribute to the majority of cervical cancer, and a substantial proportion of cervical intraepithelial neoplasia (CIN) grades 2/3 or worse (CIN2+/CIN3+) including adenocarcinoma in situ or worse. The aim of this study was to quantify the effect of quadrivalent HPV (qHPV) vaccination on incidence of CIN2+ and CIN3+. A nationwide cohort of girls and young women resident in Sweden 2006–2013 and aged 13–29 (n = 1,333,691) was followed for vaccination and histologically confirmed high‐grade cervical lesions. Data were collected using the Swedish nationwide healthcare registers. Poisson regression was used to calculate incidence rate ratios (IRRs) and vaccine effectiveness [(1‐IRR)x100%] comparing fully vaccinated with unvaccinated individuals. IRRs were adjusted for attained age and parental education, and stratified on vaccination initiation age. Effectiveness against CIN2+ was 75% (IRR = 0.25, 95%CI = 0.18–0.35) for those initiating vaccination before age 17, and 46% (IRR = 0.54, 95%CI = 0.46–0.64) and 22% (IRR = 0.78, 95%CI = 0.65–0.93) for those initiating vaccination at ages 17–19, and at ages 20–29, respectively. Vaccine effectiveness against CIN3+ was similar to vaccine effectiveness against CIN2+. Results were robust for both women participating to the organized screening program and for women at prescreening ages. We show high effectiveness of qHPV vaccination on CIN2+ and CIN3+ lesions, with greater effectiveness observed in girls younger at vaccination initiation. Continued monitoring of impact of HPV vaccination in the population is needed in order to evaluate both long‐term vaccine effectiveness and to evaluate whether the vaccination program achieves anticipated effects in prevention of invasive cervical cancer.

Objectives To assess whether the increased sensitivity of screening for human papillomavirus (HPV) may represent overdiagnosis and to compare the long term duration of protective effect against cervical intraepithelial neoplasia grade 2 or worse (CIN2+) in HPV based and cytology based screening.Design 13 year follow-up of the Swedescreen randomised controlled trial of primary HPV screening.Setting Organised cervical screening programme in Sweden.Participants 12 527 women aged 32-38 attending organised screening were enrolled and randomised to HPV and cytology double testing (intervention arm, n=6257) or to cytology only, with samples frozen for future HPV testing (control arm, n=6270). Main outcome measuresCumulative incidence of CIN2+ and CIN3+ (Kaplan Meier curves). Longitudinal test characteristics were calculated for cytology only, HPV testing only, and cytology and HPV testing combined, adjusting for censoring. ResultsThe increased detection of CIN2+ in the intervention arm decreased over time. After six years, the cumulative incidence of CIN3+ was similar in both trial arms, and after 11 years the cumulative incidence of CIN2+ became similar in both arms. The longitudinal sensitivity of cytology for CIN2+ in the control arm at three years was similar to the sensitivity of HPV testing in the intervention arm at five years of follow-up: 85.94% (95% confidence interval 76.85% to 91.84%) v 86.40% (79.21% to 91.37%). The sensitivity of HPV screening for CIN3+after five years was 89.34% (80.10% to 94.58%) and for cytology after three years was 92.02% (80.59% to 96.97%). ConclusionsOver long term follow-up, the cumulative incidence of CIN2+ was the same for HPV screening and for cytology, implying that the increased sensitivity of HPV screening for CIN2+ reflects earlier detection rather than overdiagnosis. The low long term risks of CIN3+ among women who tested negative in HPV screening, support screening intervals of five years for such women. Trial registration Clinicaltrials.gov NCT00479375. IntroductionCervical screening using cytology has resulted in a noticeable reduction in cervical cancer. However, there are still about 55 000 annual cases of cervical cancer in the European region. 1Infection with oncogenic types of human papillomavirus (HPV) is a necessary risk factor in cervical carcinogenesis 2 and testing for HPV DNA has a higher sensitivity for detection of cervical intraepithelial neoplasia, the precursor lesion of cervical cancer.3-6 Therefore HPV based cervical screening might possibly enable screening programmes with an increased protective effect against cervical cancer. Because HPV infection precedes the development of cervical intraepithelial neoplasia, 7 it is conceivable that HPV based screening could be performed with longer screening intervals, which in turn could result in more cost effective screening. 8Randomised controlled trials of HPV based screening have found that the initial higher detection of cervical intraepithelial neoplasia grade 3 or worse (CIN3+) is followed by a r...

BackgroundIncidence of condyloma, or genital warts (GW), is the earliest possible disease outcome to measure when assessing the effectiveness of human papillomavirus (HPV) vaccination strategies. Efficacy trials that follow prespecified inclusion and exclusion criteria may not be fully generalizable to real-life HPV vaccination programs, which target a broader segment of the population. We assessed GW incidence after on-demand vaccination with quadrivalent HPV vaccine using individual-level data from the entire Swedish population.MethodsAn open cohort of girls and women aged 10 to 44 years living in Sweden between 2006 and 2010 (N > 2.2 million) was linked to multiple population registers to identify incident GW in relation to HPV vaccination. For vaccine effectiveness, incidence rate ratios of GW were estimated using time-to-event analyses with adjustment for attained age and parental education level, stratifying on age at first vaccination.ResultsA total of 124 000 girls and women were vaccinated between 2006 and 2010. Girls and women with at least one university-educated parent were 15 times more likely to be vaccinated before age 20 years than girls and women whose parents did not complete high school (relative risk ratio = 15.45, 95% confidence interval [CI] = 14.65 to 16.30). Among those aged older than 20 years, GW rates declined among the unvaccinated, suggesting that HPV vaccines were preferentially used by women at high risk of GW. Vaccination effectiveness was 76% (95% CI = 73% to 79%) among those who received three doses of the vaccine with their first dose before age 20 years. Vaccine effectiveness was highest in girls vaccinated before age 14 years (effectiveness = 93%, 95% CI = 73% to 98%).ConclusionsYoung age at first vaccination is imperative for maximizing quadrivalent HPV vaccine effectiveness.