Continued HPV vaccination in the face of unexpected challenges: A commentary on the rationale for an extended interval two-dose schedule

Immunogenicity and Safety of Extended-Interval 2-Dose Regimens of 9vHPV Vaccine

BACKGROUND

Nine-valent human papillomavirus (9vHPV) vaccines can be administered in 2 doses 6 to 12 months apart in adolescents. The impact of extended dose intervals is unknown. We report immunogenicity and safety data in adolescents of a second 9vHPV vaccine dose administered ≥1 year after the first.

METHODS

This open-label safety and immunogenicity study (NCT04708041) assessed extended-interval 2-dose regimens of 9vHPV vaccine among adolescents (10 to 15 years) who received 2 9vHPV vaccine doses: the first ≥1 year before enrollment, and second, at enrollment (day 1). We measured serologic responses to vaccine-targeted human papillomavirus (HPV) types at enrollment day 1 (pre-dose 2) and 1 month post-dose 2 (month 1) using a competitive LuminexV® immunoassay. We estimated effects of dose interval on geometric mean titers (GMTs) using regression modeling. Participants reported adverse events (AEs) through 15 days after vaccination.

RESULTS

We enrolled 146 adolescents (mean age 13.3 years) with median 25 months since first 9vHPV vaccine dose (range: 12-53 months). Across vaccine-targeted HPV types, GMTs increased from day 1 to month 1; seropositivity at month 1 was 100%. Anti-HPV GMTs at month 1 were not affected by differences in dose interval of 12 to 53 months, based on regression modeling. The most common AEs were mild-to-moderate injection site reactions; no serious AEs were reported.

CONCLUSIONS

Extending the interval between first and second 9vHPV vaccine doses to 12 to 53 months did not affect antibody responses, with favorable safety profile. These results support feasibility of extended interval regimens for 9vHPV vaccine.

Potential benefit of extended dose schedules of human papillomavirus vaccination in the context of scarce resources and COVID-19 disruptions in low-income and middle-income countries: a mathematical modelling analysis

BACKGROUND

The WHO Strategic Advisory Group of Experts recommended that an extended interval of 3-5 years between the two doses of the human papillomavirus (HPV) vaccine could be considered to alleviate vaccine supply shortages. However, three concerns have limited the introduction of extended schedules: girls could be infected between the two doses, the vaccination coverage for the second dose could be lower at ages 13-14 years than at ages 9-10 years, and identifying girls vaccinated with a first dose to give them the second dose could be difficult. Using mathematical modelling, we examined the potential effect of these concerns on the population-level impact and efficiency of extended dose HPV vaccination schedules.

METHODS

We used HPV-ADVISE, an individual-based, transmission-dynamic model of multitype HPV infection and disease, calibrated to country-specific data for four low-income and middle-income countries (India, Viet Nam, Uganda, and Nigeria). For the extended dose scenarios, we varied the vaccination coverage of the second dose among girls previously vaccinated, the one-dose vaccine efficacy, and the one-dose vaccine duration of protection. We also examined a strategy in which girls aged 14 years were vaccinated irrespective of their previous vaccination status. We used a scenario of girls-only two-dose vaccination at age 9 years (vaccine=9 valent, vaccine-type efficacy=100%, duration of protection=lifetime, and coverage=80%) as our comparator. We estimated two outcomes: the relative reduction in the age-standardised cervical cancer incidence (population-level impact) and the number of cervical cancers averted per 100 000 doses (efficiency).

FINDINGS

Our model projected substantial reductions in cervical cancer incidence over 100 years with the two-dose schedule (79-86% depending on the country), compared with no vaccination. Projections for the 5-year extended schedule, in which the second dose is given only to girls previously vaccinated at age 9 years, were similar to the current two-dose schedule, unless vaccination coverage of the second dose is very low (reductions in cervical cancer incidence of 71-78% assuming 30% coverage at age 14 years among girls vaccinated at age 9 years). However, when the dose at age 14 years is given to girls irrespective of vaccination status and assuming high vaccination coverage, the model projected a substantially greater reduction in cervical cancer incidence compared with the current two-dose schedule (reductions in cervical cancer incidence of 86-93% assuming 70% coverage at age 14 years, irrespective of vaccination status). Efficiency of the extended schedule was greater than the two-dose schedule, even with a drop in vaccination coverage.

INTERPRETATION

The three concerns are unlikely to have a substantial effect on the population-level impact of extended dose schedules. Hence, extended dose schedules will likely provide similar cervical cancer reductions as two-dose schedules, while reducing the number of doses required in the short-term, providing a more efficient use of scarce resources, and offering a 5-year time window to reassess the necessity of the second dose.

FUNDING

WHO, Canadian Institute of Health Research Foundation, Fonds de recherche du Québec-Santé, Digital Research Alliance of Canada, and Bill & Melinda Gates Foundation.

Prostate cancer and the human papilloma virus: causative association, role of vaccines, and the impact of the COVID-19 pandemic

Prostate cancer affects a significant proportion of men worldwide. Evidence from genetic and clinical studies suggests that there may be a causal association between prostate cancer and the human papilloma virus (HPV). As HPV is a vaccine-preventable pathogen, the possibility of a role in prostate cancer causation may reinforce the importance of effective HPV vaccination campaigns. This is of particular relevance in light of the COVID-19 pandemic, which may have considerable effects on HPV vaccine uptake and distribution.

Non-inferior antibody levels for HPV16/18 after extended two-dose schedules compared with a six-month interval: findings of a systematic review and meta-analysis

Protection after human papillomavirus (HPV) vaccination can be maximized by optimizing vaccination schedules. We systematically reviewed immunogenicity and effectiveness of HPV vaccines administered 6 months apart compared with longer intervals. Seroconversion to vaccine-type HPV was non-inferior for 12- compared with 6-month intervals, but inconclusive for comparison of 36-96 months with 6 months. A 12-month interval showed non-inferior (margin 0.5) vaccine-type HPV antibody responses compared with a 6-month interval. Compared to 6 months, an interval of 36-96 months resulted in non-inferior antibody responses for HPV6 and high-risk types HPV16 and 18, but did not lead to a non-inferior antibody response for HPV11 (GMR 0.63, 95% CI:0.41-0.97). Data on the effectiveness of extended two-dose schedules were limited. Our findings indicate that HPV immunization programs could adopt a 12-month interval instead of 6 months for increased flexibility without compromising immunogenicity. Further evaluation to confirm the immunogenicity and effectiveness of intervals beyond 12 months is warranted.

Design of a Phase III immunogenicity and safety study evaluating two-dose regimens of 9-valent human papillomavirus (9vHPV) vaccine with extended dosing intervals

HPV vaccines are widely licensed as two-dose regimens, 6-12 months apart, for adolescents. Extended intervals between doses may be necessary due to resource constraints or vaccination program disruption. This international, multicenter, open-label study (NCT04708041) will evaluate the safety and immunogenicity of two-dose 9vHPV vaccine regimens with extended intervals of 1-5 years between doses in boys/girls compared with a standard three-dose regimen in women. Participants (planned N = 700) will be enrolled into six cohorts; Cohort 0: boys/girls aged 10-15 years who received one 9vHPV vaccine dose ≥1 year before enrollment without completing the series will receive one study dose of 9vHPV vaccine at day 1; Cohorts 1-4: HPV vaccination-naïve boys/girls aged 9-14 years will receive two doses (day 1 and month 12, 24, 36, or 60); Cohort 5: HPV vaccination-naïve women aged 16-26 years will receive three doses (day 1, months 2 and 6). Primary analyses will be based on serological responses 1 month after final vaccine dose. Co-primary objectives will (1) evaluate non-inferiority of geometric mean titers in each of Cohorts 1-4 versus Cohort 5, and (2) characterize antibody responses in Cohort 0, accounting for the interval between commercial and study vaccine dose. Injection-site and systemic adverse events (AEs) will be collected for 15 days and serious AEs for 12 months post-vaccination; vaccine-related serious AEs and deaths will be collected throughout the study. Results will inform completion of vaccination in individuals who did not complete the recommended series and guide implementation of vaccination programs in resource-limited settings.