Different Challenges in Eliminating HPV16 Compared to Other Types: A Modeling Study

Vaccination and screening strategies to accelerate cervical cancer elimination in Norway: a model-based analysis

BACKGROUND

Experts have proposed an 'EVEN FASTER' concept targeting age-groups maintaining circulation of human papillomavirus (HPV). We explored effects of the vaccination component of these proposals compared with cervical cancer (CC) screening-based interventions on age-standardized incidence rate (ASR) and CC elimination (<4 cases/100,000) timing in Norway.

METHODS

We used a model-based approach to evaluate HPV vaccination and CC screening scenarios compared with a status-quo scenario reflecting previous vaccination and screening. For cohorts ages 25-30 years, we examined 6 vaccination scenarios that incrementally increased vaccination coverage from current cohort-specific rates. Each vaccination scenario was coupled with three screening strategies that varied screening frequency. Additionally, we included 4 scenarios that alternatively increased screening adherence. Population- and cohort-level outcomes included ASR, lifetime risk of CC, and colposcopy referrals.

RESULTS

Several vaccination strategies coupled with de-intensified screening frequencies lowered ASR, but did not accelerate CC elimination. Alternative strategies that increased screening adherence could both accelerate elimination and improve ASR.

CONCLUSIONS

The vaccination component of an 'EVEN FASTER' campaign is unlikely to accelerate CC elimination in Norway but may reduce population-level ASR. Alternatively, targeting under- and never-screeners may both eliminate CC faster and lead to greater health benefits compared with vaccination-based interventions we considered.

Scientific approaches toward improving cervical cancer elimination strategies

At the 2023 EUROGIN workshop scientific basis for strategies to accelerate the elimination of cervical cancer and its causative agent, human papillomavirus (HPV) were reviewed. Although some countries have reached key performance indicators toward elimination (>90% of girls HPV vaccinated and >70% of women HPV screened), most are yet to reach these targets, implying a need for improved strategies. Gender-neutral vaccination, even with moderate vaccination coverage was highlighted as a strategy to achieve elimination more rapidly. It is more resilient against major disturbances in vaccination delivery, such as what happened during the coronavirus pandemic. Further, an analysis of ethical/legal issues indicated that female-restricted vaccination is problematic. Extended catch-up of vaccination with concomitant screening, and outreach to vulnerable groups were highlighted. Although birth cohorts with high coverage of HPV vaccination at school are protected against HPV, and HPVs have a very low reproductive rate in women above age 35, adult women below age 30 have inadequate direct protection. In addition to herd protection from gender-neutral vaccination, this group can be protected by offering concomitant catch-up HPV vaccination and HPV screening. Furthermore, hepatitis B vaccination experiences indicate that elimination cannot be achieved without prioritizing vulnerable/migrant populations. The long-lasting durability of vaccination-induced antibody responses suggests prolonged protection with HPV vaccines when adequately administrated. Finally, cost-effectiveness modelling suggests that high-coverage HPV vaccination in multiple population segments will be resource-saving due to reduced need for screening. In summary, the workshop found that strategically optimal deployment of vaccination will accelerate elimination of HPV and cervical cancer.

Gender neutral HPV vaccination programs: Reconsidering policies to expand cancer prevention globally

Human papillomavirus (HPV) infection is responsible for many cancers in both women and men. Cervical cancer, caused by HPV, is the fourth most common cancer among women worldwide, even though it is one of the most preventable cancers. Prevention efforts include HPV vaccination, however these programs remain nascent in many countries. In 2020 the World Health Assembly adopted the Global Strategy for cervical cancer elimination including a goal to fully vaccinate 90% of girls with the HPV vaccine by the age of 15. However, very few countries have reached even 70% coverage. Increased vaccine availability in the future may allow the opportunity to vaccinate more people. This could add to the feasibility of introducing gender-neutral HPV vaccination programs. Adopting a gender-neutral HPV vaccine approach will reduce HPV infections transmitted among the population, combat misinformation, minimize vaccine-related stigma, and promote gender equity. We propose approaching programmatic research through a gender-neutral lens to reduce HPV infections and cancers and promote gender equality. In order to design more effective policies and programs, a better understanding of the perspectives of clients, clinicians, community leaders, and policy-makers is needed. A clear, multi-level understanding of these stakeholders' views will facilitate the development of target policy and programs aimed at addressing common barriers and optimizing uptake. Given the benefit of developing gender-neutral HPV vaccination programs to eliminate cervical cancer and address other HPV associated cancers, we must build knowledge through implementation research around this topic to inform policy-makers and funders for future policy shifts.

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

BACKGROUND

Cervical cancer elimination through human papillomavirus (HPV) vaccination programs requires the attainment of herd effect. Due to its uniquely high basic reproduction number, the vaccination coverage required to achieve herd effect against HPV type 16 exceeds what is attainable in most populations. We have compared how gender-neutral and girls-only vaccination strategies create herd effect against HPV16 under moderate vaccination coverage achieved in a population-based, community-randomized trial.

METHODS AND FINDINGS

In 2007-2010, the 1992-1995 birth cohorts of 33 Finnish communities were randomized to receive gender-neutral HPV vaccination (Arm A), girls-only HPV vaccination (Arm B), or no HPV vaccination (Arm C) (11 communities per trial arm). HPV16/18/31/33/35/45 seroprevalence differences between the pre-vaccination era (2005-2010) and post-vaccination era (2011-2016) were compared between all 8,022 unvaccinated women <23 years old and resident in the 33 communities during 2005-2016 (2,657, 2,691, and 2,674 in Arms A, B, and C, respectively). Post- versus pre-vaccination-era HPV seroprevalence ratios (PRs) were compared by arm. Possible outcome misclassification was quantified via probabilistic bias analysis. An HPV16 and HPV18 seroprevalence reduction was observed post-vaccination in the gender-neutral vaccination arm in the entire study population (PR16 = 0.64, 95% CI 0.10-0.85; PR18 = 0.72, 95% CI 0.22-0.96) and for HPV16 also in the herpes simplex virus type 2 seropositive core group (PR16 = 0.64, 95% CI 0.50-0.81). Observed reductions in HPV31/33/35/45 seroprevalence (PR31/33/35/45 = 0.88, 95% CI 0.81-0.97) were replicated in Arm C (PR31/33/35/45 = 0.79, 95% CI 0.69-0.90).

CONCLUSIONS

In this study we only observed herd effect against HPV16/18 after gender-neutral vaccination with moderate vaccination coverage. With only moderate vaccination coverage, a gender-neutral vaccination strategy can facilitate the control of even HPV16. Our findings may have limited transportability to other vaccination coverage levels.

TRIAL REGISTRATION

ClinicalTrials.gov number NCT00534638, https://clinicaltrials.gov/ct2/show/NCT00534638.

Differing Age-Specific Cervical Cancer Incidence Between Different Types of Human Papillomavirus: Implications for Predicting the Impact of Elimination Programs

The elimination of cervical cancer rests on high efficacy of human papillomavirus (HPV) vaccines. The HPV type distribution among cases of invasive cervical cancer (ICC) is used to make predictions about the impact of eliminating different types of HPV, but accumulating evidence of differences in age-specific cancer incidence by HPV type exists. We used one of the largest population-based series of HPV genotyping of ICCs (n = 2,850; Sweden, 2002–2011) to estimate age-specific ICC incidence by HPV type and obtain estimates of the cancer-protective impact of the removal of different HPV types. In the base case, the age-specific ICC incidence had 2 peaks, and the standardized lifetime risk (SLTR, the lifetime number of cases per birth cohort of 100,000 females) for HPV-positive ICC was 651 per 100,000 female births. In the absence of vaccine types HPV 16 and HPV 18, the SLTR for ICC was reduced to 157 per 100,000 female births (24% of HPV-positive SLTR). Elimination of all 9 types that can currently be vaccinated against reduced the remaining SLTR to 47 per 100,000 female births (7%), the remaining ICC incidence only slowly increasing with age. In conclusion, after elimination of vaccine-protected HPV types, very few cases of ICC will be left, especially among fertile, reproductive-age women.

From cervical cancer elimination to eradication of vaccine-type human papillomavirus: Feasibility, public health strategies and cost-effectiveness

The Director-General of the World Health Organization has called for global action towards elimination of cervical cancer as a public health problem. Cervical cancer is caused by human papillomavirus (HPV), an infectious agent with no non-human reservoir. One way to achieve this is through very high levels of vaccine coverage that could enable global eradication of vaccine-type HPV. Using the case study of India, we show that HPV eradication can meet all the Dahlem and Strüngmann criteria for feasibility of eradication. It can be achieved with 90% gender-neutral HPV vaccine coverage together with 95% coverage in high-risk groups such as female sex workers. Such a strategy would likely be cost-effective compared to no vaccination. Although it would be more costly in the short-term than achieving cervical cancer elimination alone, it would save costs in the long-term by removing or at least sharply reducing the need for preventive measures.

Universal Human Papillomavirus Vaccination and its Impact on the Southern Italian Region

HPV is still the most common sexually transmitted infection, leading to the onset of many disorders while causing an increase in direct and indirect health costs. High Risk (HR) HPV is the primary cause of invasive cervical cancer and contributes significantly to the development of anogenital and oropharyngeal cancers. The introduction of universal HPV vaccination has led to a significant reduction in vaccine-targeted HPV infections, cross-protective genotypes, precancerous lesions and anogenital warts. Despite the several limitations of HPV vaccination programs, including vaccine type specificity, different schedules, target age-groups and poor communication, the impact has become increasingly evident, especially in countries with high vaccine uptake. We carried out a review of the most recent literature to evaluate the effects of HPV vaccination on vaccinetargeted HPV genotypes and to assess the level of cross-protection provided against non-vaccine HPV types. Subsequently, to assess the rates of HPV infection in a southeast Italian region, we performed an epidemiological investigation on the impact of vaccination on genotypes and on the prevalence and distribution of HPV infection during the twelve-year period 2006-2017 in the Local Health Unit (LHU) of Lecce. The vaccination coverage of about 70% among girls in the LHU led to an initial reduction in vaccine-targeted HPV types and cross-protective genotypes. However, the results on this population should be interpreted cautiously because the period since the start of vaccination is too short and the coverage rate is not yet optimal to evaluate the efficacy of vaccination in lowering the prevalence of non-vaccine HR HPV types in the vaccinated cohort and in older subjects. Nevertheless, it is expected that direct effects will increase further and that herd immunity will begin to emerge as vaccination coverage increases.

Diversity of human papillomavirus typing among women population living in rural and remote areas of Brazilian territory

Objectives

Genotyping HPV from samples tested positive to careHPV™ assay in rural and remote areas of Brazilian territory.

Methods

A total of 5079 women were enrolled in an opportunistic screening from the Barretos Cancer Hospital, through mobile units or ambulatory unit. All careHPV™ hr-HPV positive samples were tested by a Luminex-based protocol in order to evaluate the HPV infecting types.

Results

Positive hr-HPV results were obtained in 10.6% (536/5068) of women. Among these cases, HPV-56 and HPV-51 were the most common types detected in 32.3% and 31.4%, respectively. HPV-53 (20.5%), HPV-18 (18.5%), HPV-58 (17.6%), HPV-52 (16.0%) and HPV-16.6%) were the other most frequent types detected. These frequencies represent prevalences of 2.35%, 2.12%, 2.02%, 1.84% and 1.80% respectively, within the population studied. Regarding low-risk HPVs, HPV-6 was detected in 12.9% of the samples. The less frequent types (<3%) were: HPV-70, HPV-11 and HPV-26.

Conclusions

The most frequent types detected were: HPV-56, HPV-51, HPV-53, HPV-18, HPV-58, HPV-52 and HPV-16 according to decreasing rates.

Regional variations in human papillomavirus prevalence across time in NHANES (2003-2014)

INTRODUCTION

The consequences of low human papillomavirus (HPV) vaccination in Census regions with higher incidence of cervical cancer may contribute to continued disparities. Our purpose was to evaluate regional variations in HPV prevalence across time.

METHODS

Repeated cross-sectional data from the National Health and Nutrition Examination Survey (NHANES), 2003-2014 were examined. Participants included females 14 to 34 years old who provided adequate vaginal samples for HPV DNA typing (N = 6387). Region of residence and HPV vaccination status associations with HPV prevalence were examined using chi-square and multivariable logistic regression. HPV types were grouped according to vaccine-type HPV (types 6, 11, 16, 18) and risk (high or low-risk). Time and vaccination status were included in subsequent models for post-licensure survey cycles (2007-2014) to assess their effects on observed associations.

RESULTS

No decreases in vaccine-type HPV prevalence were found between the prevaccine cycles (2003-2006) and early post-licensure cycles (2007-2010, p > 0.05). Vaccine-type HPV prevalence decreased in late post-licensure years (2011-2014) compared to prevaccine years (2003-2006, p = 0.001). The highest prevalence of vaccine-type HPV occurred in the South (8.6%) and Midwest (8.6%), followed by the West (4.8%), and the Northeast (3.5%) in late post-licensure years. Lower odds of vaccine-type HPV across time in post-licensure survey cycles were found to be attributable to time, and more strongly to HPV vaccination.

CONCLUSIONS

There were regional variations in vaccine-type HPV prevalence between prevaccine and post-licensure years. These decreases appeared to be at least partially attributable to HPV vaccination. Programs are needed to address geographical disparities in HPV vaccination.

Potential effectiveness of prophylactic HPV immunization for men who have sex with men in the Netherlands: A multi-model approach

BACKGROUND

Men who have sex with men (MSM) are at high risk for anal cancer, primarily related to human papillomavirus genotype 16 (HPV16) infections. At 8.5 per 100,000 per year, the incidence rate of anal cancer among MSM is similar to that of cervical cancer among adult women in the Netherlands. However, MSM are not included in most HPV vaccination programs. We explored the potential effectiveness of prophylactic immunization in reducing anogenital HPV16 transmission among MSM in the Netherlands.

METHODS AND FINDINGS

We developed a range of mathematical models for penile-anal HPV16 transmission, varying in sexual contact structure and natural history of infection, to provide robust and plausible predictions about the effectiveness of targeted vaccination. Models were informed by an observational cohort study among MSM in Amsterdam, 2010-2013. Parameters on sexual behavior and HPV16 infections were obtained by fitting the models to data from 461 HIV-negative study participants, considered representative of the local MSM population. We assumed 85% efficacy of vaccination against future HPV16 infections as reported for HIV-negative MSM, and age-specific uptake rates similar to those for hepatitis B vaccination among MSM in the Netherlands. Targeted vaccination was contrasted with vaccination of 12-year-old boys at 40% uptake in base-case scenarios, and we also considered the effectiveness of a combined strategy. Offering vaccine to MSM without age restrictions resulted in a model-averaged 27.3% reduction (90% prediction interval [PI] 11.9%-37.5%) in prevalence of anal HPV16 infections, assuming similar uptake among MSM as achieved for hepatitis B vaccination. The predicted reduction improved to 46.1% (90% PI 21.8%-62.4%) if uptake rates among MSM were doubled. The reductions in HPV16 infection prevalence were mostly achieved within 30 years of a targeted immunization campaign, during which they exceeded those induced by vaccinating 40% of preadolescent boys, if started simultaneously. The reduction in anal HPV16 prevalence amounted to 74.8% (90% PI 59.8%-93.0%) under a combined vaccination strategy. HPV16 prevalence reductions mostly exceeded vaccine coverage projections among MSM, illustrating the efficiency of prophylactic immunization even when the HPV vaccine is given after sexual debut. Mode of protection was identified as the key limitation to potential effectiveness of targeted vaccination, as the projected reductions were strongly reduced if we assumed no protection against future infections in recipients with prevalent infection or infection-derived immunity at the time of immunization. Unverified limitations of our study include the sparsity of data to inform the models, the omission of oral sex in transmission to the penile or anal site, and the restriction that our modeling results apply primarily to HIV-negative MSM.

CONCLUSIONS

Our findings suggest that targeted vaccination may generate considerable reductions in anogenital HPV16 infections among MSM, and has the potential to accelerate anal cancer prevention, especially when combined with sex-neutral vaccination in preadolescence.

Eradication of human papillomavirus and elimination of HPV-related diseases - scientific basis for global public health policies

INTRODUCTION

Infections with oncogenic human papillomaviruses (HPV) globally cause about 9% of cancers in females and 1% of cancers in males. HPV disease burden can be effectively controlled by prophylactic HPV-vaccination provided it has high impact.

AREAS COVERED

A unique series of biobank-based and health registry-based studies that exploit randomized intervention cohorts has provided data on population-level safety of HPV vaccination, duration of vaccine-induced protection and impact of gender-neutral HPV vaccination, providing a scientific basis for policies to eradicate oncogenic HPV types and associated diseases worldwide.

EXPERT COMMENTARY

The ultimate goal of HPV vaccination is the eradication of high-risk (hr) HPVs. Seventy-five percent coverage gender-neutral vaccination of early adolescents will rapidly eradicate also HPV16 from the general population.

Gender-neutral vaccination provides improved control of human papillomavirus types 18/31/33/35 through herd immunity: Results of a community randomized trial (III)

With optimal strategy, human papillomavirus (HPV) vaccines have the potential to control HPV. We have assessed vaccine efficacy (VE), herd effect (HE) of HPV vaccination and overall protective effectiveness (PE) against high-risk HPV infections by HPV type and vaccination strategy in a community-randomized trial using the bivalent HPV16/18 vaccine. We randomized 33 communities to gender-neutral HPV vaccination (Arm A), HPV vaccination of girls and hepatitis B-virus (HBV) vaccination of boys (Arm B) and gender-neutral HBV vaccination (Arm C). Entire 1992-1995 male (40,852) and female (39,420) birth cohorts were invited, and 11,662 males and 20,513 females vaccinated with 20-30% and 45% coverage in 2007-2010. During 2010-2014, 11,396 cervicovaginal samples were collected from 13,545 18.5-year-old attendees. HPV typing was performed by a high-throughput PCR. VE was calculated for HPV vaccinated women and HE for non-HPV-vaccinated women, using the HBV vaccinated, for HE all non-HPV vaccinated, Arm C women as controls. PE was calculated as coverage rate-weighted mean of VE + HE. HPV16/18/45 and 31/33/35 VEs varied between 86-94% and 30-66%, respectively. Only the gender-neutral vaccination provided significant HEs against HPV18 (61%) and HPV31 (72%) in the 1995 birth cohort-increased HEs against HPV33 (39%) and HPV35 (42%) were also observed. Due to the increased HEs, PEs for HPV16/18/45 and HPV31/33/35 were comparable in the gender-neutral arm 1995 birth cohort. High vaccine efficacy against HPV16/18/45 and, gender-neutral vaccination-enforced, herd effect against HPV18/31/33/35 by the bivalent vaccine rapidly provides comparable overall protective effectiveness against six oncogenic HPV types: 16/18/31/33/35/45.

Impacts of human papillomavirus vaccination for different populations: A modeling study

International variations in the prevalence of HPV infection derive from differences in sexual behaviors, which are also a key factor of the basic reproductive number (R0 ) of HPV infection in different populations. R0 affects the strength of herd protection and hence the impact of a vaccination program. Similar vaccination programs may therefore generate different levels of impact depending upon the population's pre-vaccination HPV prevalence. We used IARC's transmission model to estimate (i) the overall effectiveness of vaccination versus no vaccination in women aged 15-34 years measured as percent prevalence reduction (%PR) of HPV16 and (ii) the corresponding herd protection in populations with gender-equal or traditional sexual behavior and with different levels of sexual activity, corresponding to pre-vaccination HPV16 prevalence from 1 to 8% as observed worldwide. Between populations with different levels of gender-equal sexual activity, the highest difference in %PR under girls-only vaccination is observed at 40% coverage (91%PR vs. 48%PR for 1% and 8% pre-vaccination prevalence, respectively). HPV16 elimination is obtained with 55 and 97% coverage, respectively. To achieve desirable levels of HPV16 prevalence after vaccination, different levels of coverage are required in populations with different levels of pre-vaccination HPV16 prevalence, for example, in populations with gender-equal sexual behavior a decrease to 1/1000 HPV16 from pre-vaccination prevalence of 1 and 8% would require coverages of 37 and 96%, respectively. In traditional populations, corresponding coverages would need to be 28 and 93%, respectively. In conclusion, pre-vaccination HPV prevalence strongly influences herd immunity and helps predict the overall effectiveness of HPV vaccination.

Decline of HPV infections in Scandinavian cervical screening populations after introduction of HPV vaccination programs

OBJECTIVE

To monitor the changes in prevalence of human papillomavirus (HPV) infections in women <50 years of age, participating in cervical screening programs of Denmark, Norway, and Sweden, before and after introduction of quadrivalent HPV (qHPV) vaccination.

METHODS

Liquid-based cytology samples were collected from 6538 women who attended cervical screening in Denmark, Norway, and Sweden in 2006-2008 and from 6332 similarly enrolled women in 2012-2013. Denmark started organized qHPV vaccination in 2008, Norway in 2009, and Sweden in 2012. All HPV testing and genotyping was performed using identical enrollment and analysis methods, by accredited general primer polymerase chain reaction methods with typing using the Luminex system.

RESULTS

Overall HPV positivity declined slightly from 36.5% in 2006-2008 to 34.5% in 2012-2013. The decline was most pronounced among women 18-26 years of age: from 54.4% to 48.1% (P < 0.001). The decline was substantial for vaccine HPV types (HPV6/11/16/18: decline from 22.3% to 16.6%; P < 0.001) and was seen for both low-risk vaccine types (HPV6/11 declined from 5.0% to 2.5%) and high-risk vaccine types (HPV16/18 declined from 18.9% to 14.9%). Among women 27-50 years of age, there was no change between the time periods (22.5% and 21.6%, respectively). The significant decline in the younger age group was different in the 3 countries.

CONCLUSION

This population-based study enrolling >12,000 women participating in cervical screening in the 3 Nordic countries before and after introduction of organized qHPV vaccination demonstrated a marked decline in HPV infection in the younger population in the 2 countries where qHPV vaccination programs started in 2008-2009, suggesting that organized HPV vaccination programs resulted in a decrease of HPV types circulating in the general population.

Human papillomavirus vaccination and the role of herd effects in future cancer control planning: a review

INTRODUCTION

Vaccine herd effects are the indirect protection that vaccinated persons provide to those who remain susceptible to infection, due to the reduced transmission of infections. Herd effects have been an important part of the discourse on how to best implement human papillomavirus (HPV) vaccines and prevent HPV-related diseases.

AREAS COVERED

In this paper, we review the theory of HPV vaccine herd effects derived from mathematical models, give an account of observed HPV vaccine herd effects worldwide, and examine the implications of vaccine herd effects for future cervical cancer screening efforts.

EXPERT COMMENTARY

HPV vaccine herd effects improve the cost-effectiveness of vaccinating preadolescent girls, but contribute to making gender-neutral vaccination less economically efficient. Vaccination coverage and sexual mixing patterns by age are strong determinants of herd effects. Many countries worldwide are starting to observe reductions in HPV-related outcomes likely attributable to herd effects, most notably declining anogenital warts in young men, and declining HPV-16/18 infection prevalence in young unvaccinated women. Policy makers making recommendations for cervical cancer screening will have to consider HPV vaccination coverage and herd effects, as these will affect the positive predictive value of screening and the risk of cervical cancer in unvaccinated women.