Journal of the National Cancer Institute. Monographs最新文献

Background: In low- and middle-income countries, resource constraints remain a critical factor limiting access to cervical cancer preventive measures. The option of single-dose immunization could help improve access to human papillomavirus vaccination and attain cervical cancer elimination.

Methods: With simulation models adapted to country-specific data and scenarios for single-dose protection derived from International Agency for Research on Cancer India vaccine trial data, we estimated the expected impact of single-dose vaccination in India, Rwanda, and Brazil, three countries with varying profiles of cervical cancer risk and vaccination timelines. In combination with single-dose vaccination, we explored different resource reallocation strategies based on dose efficiency, elimination attainment, and cervical cancer cases prevented, with the existing 2-dose program as a comparator.

Results: Assuming lifelong single-dose protection, switching from 2-dose to 1-dose vaccination and reallocating resources to female catch-up could prevent 467-1336, 94-194, and 15-207 additional cervical cancer cases (per 100 000 women born) in cohorts aged 11-30 years in India, Rwanda, and Brazil, respectively. Resource reallocation to improve the current routine coverage could help eliminate cervical cancer in India and across all Brazilian states but not in Rwanda. For each country, we found a dose-efficient reallocation strategy (or a combination of strategies) together with 1-dose vaccination that could prevent more cervical cancers vs 2-dose vaccination, even in the worst-case scenario of single-dose protection.

Conclusion: Adopting single-dose vaccination with resource reallocation is a resource-efficient approach to enhance progress toward cervical cancer elimination. The overall impact of vaccination can be maximized by fine-tuning resource reallocation to a country's needs.

Background: The Costa Rica HPV Vaccine Trial provided initial evidence that 1 dose of the bivalent human papillomavirus (HPV) vaccine induces stabilizing antibody levels that may provide extended protection against HPV-16/18 infections. We report antibody seropositivity and stability 11 to 16 years after vaccination.

Methods: We invited a random subset of Costa Rica HPV Vaccine Trial participants (n = 398) who had received 3 doses and all women (n = 203) who had received 1 dose at 18 to 25 years of age to follow-up visits 11, 14, and 16 years after vaccination. We calculated HPV-16 and HPV-18 seropositivity and assessed change in enzyme-linked immunosorbent assay antibody levels 11 to 16 years after vaccination among 500 participants.

Results: By year 16, 99.4% (95% confidence interval [CI] = 96.8% to 100.0%) and 100.0% (95% CI = 98.9% to 100.0%) of 1-dose and 3-dose recipients, respectively, were HPV-16 seropositive and 98.8% (95% CI = 95.9% to 99.9%) and 100% (95% CI = 98.9% to 100.0%) of 1-dose and 3-dose recipients, respectively, were HPV-18 seropositive. Between years 11 and 16, women who had received 3 doses had a small but statistically significant decrease in the geometric mean concentration for HPV-16 of ‒12.4% (95% CI = ‒16.3% to ‒8.4%) and HPV-18 of ‒13.4% (95% CI = ‒17.2% to ‒9.4%). Among women who had received 1 dose, the decrease was statistically significant for HPV-16 at ‒8.9 (95% CI = ‒14.2% to ‒3.1%) but nonsignificant for HPV-18. Geometric mean concentration ratios of 3:1 dose (year 16) were 3.0 and 2.2 for HPV-16 and HPV-18, respectively.

Conclusions: HPV-16/18 seropositivity remained exceedingly high 16 years after vaccination. Over 5 years, small declines in antibodies were observed. Women should have protection for at least 20 years and likely much longer at the observed rate of decline.

Background: A concern in high-income countries is that switching to 1-dose human papillomavirus (HPV) vaccination could cause a rebound in HPV infection and cervical cancer if 1-dose efficacy or duration were inferior to 2 doses. Using mathematical modeling and up-to-date trial-based data, we projected the population-level effectiveness of switching from 2-dose to 1-dose vaccination under different vaccine efficacy and duration assumptions in high-income countries.

Methods: We used HPV-ADVISE (Agent-based Dynamic model for VaccInation and Screening Evaluation), a transmission-dynamic model of HPV infection and cervical cancer, varying key model assumptions to identify those with the greatest impact on projections of HPV-16 and cervical cancer incidence over time: 1) 1-dose vaccine efficacy and vaccine duration, 2) mechanisms of vaccine efficacy and duration over time, 3) midadult (>30 years of age) sexual behavior, 4) progression to cervical cancer among midadults, and 5) vaccination coverage and programs.

Results: In high-income countries, 1-dose vaccination would cause no appreciable rebound in HPV-16 infection, except for a limited rebound under the most pessimistic assumptions of vaccine duration (average, 25 years), because 1) the switch would occur when HPV prevalence is low because of high 2-dose vaccination coverage and 2) individuals would be protected during their peak ages of sexual activity (<35 to 40 years of age). Our model projects a more limited rebound in cervical cancer because of a shift to older age at infection, resulting in fewer life-years left to potentially develop cancer. Projections were robust when varying key model assumptions.

Conclusions: High protection during peak ages of sexual activity in high-income countries would likely mitigate any potential rebounds in HPV infection and cervical cancer under the most pessimistic assumptions of 1-dose efficacy and duration.

Background: There is limited evidence on the magnitude of the potential program cost savings associated with the World Health Organization-endorsed single-dose schedule for the human papillomavirus (HPV) vaccine. The objective of this analysis was to model the delivery and vaccine procurement cost implications of the new schedule.

Methods: The analysis leveraged primary data during a study evaluating the HPV vaccine delivery costs and operational context in 5 countries (Ethiopia, Guyana, Rwanda, Sri Lanka, and Uganda) implementing a two-dose schedule. To estimate the cost for the single-dose schedule, we adjusted the two-dose schedule cost estimates to account for differences in the frequency of activities, whether activities differed by HPV vaccine dose or session, and differences in relative quantity or storage volume of HPV vaccines delivered. We estimated the cost per dose and cost per adolescent receiving the full (single-dose or two-dose) vaccination schedule in 2019 US dollars from a health system perspective.

Results: Modeled results found that cost per dose would increase under a single-dose schedule, whereas cost per adolescent receiving the full schedule would decrease. The financial cost for vaccine procurement and delivery per adolescent receiving the full schedule ranged from $9.64 (Sri Lanka) to $23.43 (Guyana) under a two-dose schedule and decreased to $4.84 and $12.34, respectively, under a single-dose schedule, reflecting savings up to 50%. For economic costs, the range for a single-dose schedule was $7.86 (Rwanda) to $28.53 (Guyana).

Conclusion: A single-dose HPV vaccination schedule could provide cost savings to immunization programs and enhance program affordability and sustainability.

Human papillomavirus (HPV) prophylactic vaccines were first licensed in 2006 with the primary goal of preventing HPV-related cancers, with cervical cancer accounting for the highest morbidity and mortality globally. Six HPV vaccines have been licensed; 4 of these have been prequalified by the World Health Organization, and additional products are in the pipeline. This article provides an overview of HPV vaccine coverage and current and anticipated vaccine supply vs expected demand. Given that the 2022 World Health Organization position paper on HPV vaccines includes a 1-dose regimen as an alternate schedule, we will discuss the evidence for using licensed vaccines in single-dose regimens and the approach to generating similar supportive data for other current and future vaccines. The broad adoption of a single-dose HPV vaccine regimen would expand access to vaccines by improving the supply-demand balance, increasing affordability, and simplifying logistics, which will ultimately impact HPV-related morbidity and mortality.

Background: While recommending a human papillomavirus (HPV) single-dose vaccination schedule in 2022, the World Health Organization highlighted the need for long-term follow-up studies to monitor waning of protection. We report on vaccine efficacy against HPV infections in 1-, 2-, and 3-dose schedules and protection against cervical precancers at a median follow-up of 12 years postvaccination.

Methods: This randomized multicenter study in India was originally designed to vaccinate unmarried girls aged 10-18 years with either 2 or 3 doses of quadrivalent HPV vaccine. A ministerial decree to halt vaccination in trials resulted in the creation of cohorts receiving different doses, including just a single dose. Cohorts were assessed for incident and persistent infections by genotyping cervical samples collected yearly for 4 consecutive years after participants were married. Cervical screening with an HPV test was initiated at age 25 years for married participants. Age- and site-matched unvaccinated married women were recruited to be compared with vaccinated cohorts. Vaccine efficacy was assessed using proportional incidence ratios.

Results: The number of participants in the 1-, 2- (at 0 and 6 months), and 3-dose cohorts was 4949, 4980, and 4348, respectively. Of the recipients, 71%-82% in the different cohorts were eligible to provide samples for genotyping. Vaccine efficacy against persistent HPV 16 and 18 infection was 92.0% (95% confidence interval [CI] = 87.0% to 95.0%) in 3022 recipients of the single dose; and comparable with that observed in the 2-dose arm (94.8%, 95% CI = 90.0% to 97.3%) and the 3-dose arm (95.3%, 95% CI = 90.9% to 97.5%). No high-grade precancer associated with HPV 16 and 18 was detected among vaccinated participants compared with 8 precancers detected among the unvaccinated women.

Conclusion: This observational cohort study has established that a single dose of HPV vaccine provides high protective efficacy against persistent HPV 16 and 18 infections and associated neoplasia 15 years postvaccination.

Background: The World Health Organization has endorsed single-dose human papillomavirus (HPV) vaccination, but data on the impact on HPV prevalence in high HIV burden settings are limited.

Methods: A single-dose bivalent HPV vaccine was delivered to adolescent girls in grade 10 in a schools-based campaign in 1 district in South Africa. Impact on HPV 16 and 18 prevalence was evaluated using repeat cross-sectional surveys. A clinic-based survey in girls aged 17-18 years established HPV 16 and 18 prevalence in a prevaccine population (n = 506, including 157 living with HIV) in 2019 and was repeated in the same age group and sites in a single-dose eligible population in 2021 (n = 892, including 117 with HIV). HPV DNA was detected on self-collected vaginal swabs using the Seegene Anyplex II HPV 28. Population impact was estimated overall and by HIV status using prevalence ratios adjusted for differences in sexual behavior between surveys.

Results: Single-dose vaccination campaign coverage was 72% (4807 of 6673) of eligible girls attending high school (n = 66) in the district. HPV 16 and 18 prevalence was 35% lower in the postvaccine survey overall (adjusted prevalence ratio = 0.65, 95% confidence interval [CI] = 0.51 to 0.83; P < .001) and 37% lower in those living with HIV (adjusted prevalence ratio = 0.63, 95% CI = 0.41 to 0.95; P  = .026). No protective effect was seen for nonvaccine oncogenic HPV types 33, 35, 39, 51, 52, 56, 58, 59, or 68 overall (adjusted prevalence ratio = 1.14, 95% CI = 1.03 to 1.26; P = .011) or in those living with HIV (adjusted prevalence ratio = 1.00, 95% CI = 0.83 to 1.21. P = 0.99).

Conclusion: These data provide reassuring evidence of single-dose impact on population-level HPV 16 and 18 prevalence in a South African population, irrespective of HIV status.

Background: We simulated the impact of hypothetical waning scenarios of a 1-dose human papillomavirus (HPV) vaccination paired with switching to 2-dose mitigation strategies guided by empirical vaccine trial reporting timelines.

Methods: Using 2 independent mathematical models fitted to a high-burden setting, we projected the cumulative cervical cancer cases averted over 85 years for alternative HPV vaccination scenarios under 2 program adoption timelines: 1) de novo introduction of a 1-dose HPV vaccination and 2) a switch from an existing 2-dose HPV vaccination program to a 1-dose vaccination. We assumed 80% vaccination coverage with the bivalent vaccine and an average duration of a 1-dose HPV vaccine protection of either 30 or 25 years with 100% efficacy. We varied the eligible age group(s) at program introduction and the 2-dose mitigation (single-age cohort or multi-age cohort). If needed for mitigation, reintroduction of 2-dose vaccination was assumed to occur in 2036 (ie, 30 years after initiation of the Costa Rica Vaccine Trial).

Results: Under both vaccine adoption timelines, the models projected that countries could achieve the same level of health benefits by switching to 2 doses in 2036 using a multi-age cohort approach as with initiating a 2-dose or 1-dose vaccination program with no waning. With only a single-age cohort 2-dose mitigation approach, 98%-99% of cases would be prevented compared with the health benefits of 2 doses or a noninferior, durable 1 dose.

Conclusions: Countries hesitant to adopt a 1-dose HPV vaccination program may have opportunities to leverage the benefits and efficiency of a 1-dose schedule while awaiting longer-term reporting from 1-dose durability studies, including Costa Rica Vaccine Trial.

Human papillomavirus (HPV) vaccines received regulatory approval and were recommended for use in young girls nearly 2 decades ago. Uptake is mostly high in resource-rich settings. In resource-limited settings, where the burden of cervical cancer is disproportionately high, access to and uptake of HPV vaccines are nowhere near satisfactory, despite evidence that HPV vaccination is highly cost-effective and a significant value-for-money investment. The discovery that only a single dose of the HPV vaccines may be needed to confer adequate protection may make equitable access to HPV vaccines possible. Indeed, the recent World Health Organization recommendation allowing for 1 or 2 doses is already gaining traction. This monograph aims to update the state of the science related to single-dose HPV vaccine protection and includes both primary data and modeling efforts that address key gaps in the knowledge regarding 1) durability of protection of a single dose of the HPV vaccine, 2) single-dose HPV vaccine effectiveness in both high-income and low-income settings, 3) implementation of single-dose HPV vaccination, and 4) how to accelerate control of cervical cancer by integrating a 1-time screen for cervical disease. The content published in this monograph will continue to advance the science of HPV vaccination and will be vital as new countries make informed decisions about how best to use this remarkable vaccine.