Impact of Number of Human Papillomavirus Vaccine Doses on Genital Warts Diagnoses Among a National Cohort of U.S. Adolescents

Genital Warts in Women Vaccinated against HPV in Childhood: A Systematic Review

Human papillomavirus (HPV) is the most prevalent sexually transmitted infection among young women. Notably, more than ten years after the introduction of HPV vaccination programs in Europe, it is essential to review the real-world evidence of the incidence of anogenital warts (GWs) among women vaccinated during childhood. In this systematic review, three databases were searched for studies published between January 2008 and September 2023. Nine cohort studies were included. A total of 890,320 HPV-vaccinated women and 1,922,033 unvaccinated women were evaluated. All the studies but one investigated the 4vHPV vaccine. The incidence rate of GWs in vaccinated women ranged from 0.0 to 1650 per 100,000 person-years. The highest incidence rates were found in women vaccinated with one dose at the age of 17-19 years old and in fully vaccinated women only after 19 years of age. Similar incidence values were reported among unvaccinated women. The incidence of GWs was lower when the age at first dose was 9-11 years old. This systematic review reveals that the incidence of GWs among HPV-vaccinated women is related to the age of vaccination and the number of vaccine doses received. In the post-vaccination era, epidemiological surveillance of the incidence of GWs and their genotypes is crucial.

Implementing interventions to start HPV vaccination at age 9: Using the evidence we have

Human papillomavirus (HPV) vaccination is routinely recommended for adolescents aged 11 or 12 years but can begin at age 9. On-time HPV vaccination by the thirteenth birthday has proven to be effective in preventing HPV cancer and pre-cancer. However, HPV coverage rates continue to lag behind other routinely recommended vaccinations for adolescents. A promising approach to improving coverage is to start HPV vaccination at age 9. This approach has been endorsed by the American Academy of Pediatrics and the American Cancer Society. Benefits of this approach include increased time to complete vaccination series by the thirteenth birthday, additional spacing of recommended vaccines, and a more concentrated focus on cancer prevention messaging. While promising, little is known about how and if existing evidence-based interventions and approaches can be used to promote starting HPV vaccination at age 9. Implementation science frameworks offer scientific direction in how to adapt current and develop new interventions to promote starting HPV vaccination at age 9 and accelerate dissemination and prevent HPV cancers.

Optimizing timing of adolescent vaccines: Impact of initiating HPV vaccination before Tdap or meningococcal vaccination on timely completion of the HPV vaccine series

To explore the impact on timely series completion of initiating the HPV vaccine series prior to other vaccines in the adolescent platform (Tdap or meningococcal vacccines), we created a cohort of children aged 9 in 2015 who were continuously enrolled through the age of 13 (2019) from a national administrative database of employee-sponsored insurance in the United States (MarketScan). Logistic regressions were used to predict the odds of HPV vaccine series completion among those who started the series prior to, concurrent with, or after receiving Tdap or meningococcal vaccination. The cohort included 100,857 eligible children. Compared with adolescents who received their HPV and Tdap or HPV and meningococcal vaccinations concurrently, those who received HPV prior to other vaccines had higher completion (aOR = 1.38 for Tdap, aOR 1.62 for meningococcal), while those who received their HPV vaccination after other vaccines had lower odds of HPV vaccine series completion (aOR = 0.68 for Tdap, aOR = 0.62 for meningococcal). Other factors associated with series completion included female sex, residing in an urban (vs. rural) area, residing in the Northeast, and receiving primary care from a pediatrician (vs. family medicine physician). These data indicate that beginning the HPV vaccine series prior to the adolescent platform may improve on-time series completion.

HPV vaccine recommendations by age: A survey of providers in federally qualified health centers

Clinician recommendation remains a critical factor in improving HPV vaccine uptake. Clinicians practicing in federally qualified health centers were surveyed between October 2021 and July 2022. Clinicians were asked how they recommended HPV vaccination for patients aged 9-10, 11-12, 13-18, 19-26, and 27-45 y (strongly recommend, offer but do not recommend strongly, discuss only if the patient initiates the conversation, or recommend against). Descriptive statistics were assessed, and exact binomial logistic regression analyses were utilized to examine factors associated with HPV vaccination recommendation in 9-10-y-old patients. Respondents (n = 148) were primarily female (85%), between the ages of 30-39 (38%), white, non-Hispanic (62%), advanced practice providers (55%), family medicine specialty (70%), and practicing in the Northeast (63%). Strong recommendations for HPV vaccination varied by age: 65% strongly recommended for ages 9-10, 94% for ages 11-12, 96% for ages 13-18, 82% for age 19-26, and 26% for ages 27-45 y. Compared to Women's Health/OBGYN specialty, family medicine clinicians were less likely to recommend HPV vaccination at ages 9-10 (p = .03). Approximately two-thirds of clinicians practicing in federally qualified health centers or safety net settings strongly recommend HPV vaccine series initiation at ages 9-10. Additional research is needed to improve recommendations in younger age groups.

Quadrivalent HPV vaccine effectiveness against anogenital warts: A registry-based study of 2,2 million individuals

BACKGROUND

In 2009, Norway initiated routine quadrivalent HPV (qHPV) vaccination for girls at 12-13 years of age to protect against virus types causing cervical cancer, HPV16/18, and HPV6/11 which cause anogenital warts (AGW). We wanted to investigate qHPV vaccine effectiveness (VE) against AGW in females before and after first AGW episode and to assess the impact of female vaccination in males.

MATERIALS AND METHODS

QHPV vaccination and AGW episodes were collected for the time period 2006-2016 for birth cohorts 1975-2003. Cox models were applied to age at first, as well as at second AGW episode. Finally, we estimated the impact of the female vaccination program on unvaccinated males.

RESULTS

The VE against the first episode of AGW was strongly dependent on vaccination age, with hazard ratios (HRs) compared to unvaccinated individuals of 0.2, 0.2, 0.3, 0.5, 1.0, 1.3, and 2.7, for age groups of ⩽13, 14-15, 16-17, 18-19, 20-24, 25-29, and 30+ years at first vaccination, respectively. Among women who had suffered a first episode of AGW, subsequent qHPV vaccination did not protect against a second episode, with HRs of 0.8, 1.0, and 1.4, for age groups of ⩽17, 18-24, and 25+ years at first vaccination. A gradually decreasing AGW risk was seen in unvaccinated male cohorts neighboring the first routinely vaccinated female 1997 cohort.

CONCLUSIONS

When administered before 14 years of age, qHPV vaccination reduced the probability of AGW about fivefold. The effect decreased sharply with vaccination age, and was not significant among women vaccinated after age 20 years. QHPV administered after the first AGW episode did not protect against a second AGW episode. Herd effects were indicated in unvaccinated males, as we observed a gradual decrease in AGW rates from the 1993 male birth cohort and onwards.

Human papillomavirus vaccine effectiveness by number of doses: Updated systematic review of data from national immunization programs

BACKGROUND

Human papillomavirus (HPV) vaccines were first licensed as a three-dose series. Two doses are now widely recommended in some age groups; there are data suggesting high efficacy with one dose. We updated a systematic literature review of HPV vaccine effectiveness by number of doses in observational studies.

METHODS

We searched Medline and Embase databases from January 1, 2007, through September 29, 2021. Data were extracted and summarized in a narrative synthesis. We also conducted quality assessments for bias due to selection, information, and confounding.

RESULTS

Overall, 35 studies were included; all except one were conducted within the context of a recommended three-dose schedule. Evaluations were in countries that used bivalent HPV vaccine (seven), quadrivalent HPV vaccine (27) or both (one). Nine evaluated effectiveness against HPV infection, ten anogenital warts, and 16 cervical abnormalities. All studies were judged to have moderate or serious risk of bias. The biases rated as serious would likely result in lower effectiveness with fewer doses. Investigators attempted to control for or stratify by potentially important variables, such as age at vaccination. Eight studies evaluated impact of buffer periods (lag time) for case counting and 10 evaluated different intervals between doses for two-dose vaccine recipients. Studies that stratified by vaccination age found higher effectiveness with younger age at vaccination, although differences were not all formally tested. Most studies found highest estimates of effectiveness with three doses; significant effectiveness was found among 28/29 studies that evaluated three doses, 19/29 that evaluated two doses, and 18/30 that evaluated one dose. Some studies that adjusted or stratified analyses by age at vaccination found similar effectiveness with three, two and one doses.

CONCLUSION

Observational studies of HPV vaccine effectiveness have many biases. Studies examining persons vaccinated prior to sexual activity and using methods to reduce sources of bias are needed for valid effectiveness estimates.

Real-world impact and effectiveness assessment of the quadrivalent HPV vaccine: a systematic review of study designs and data sources

INTRODUCTION

Vaccine effectiveness and impact studies are typically observational, generating evidence after vaccine launch in a real-world setting. For human papillomavirus (HPV) vaccination studies, the variety of data sources and methods used is pronounced. Careful selection of study design, data capture and analytical methods can mitigate potential bias in such studies.

AREAS COVERED

We systematically reviewed the different study designs, methods, and data sources in published evidence (1/2007-3/2020), which assessed the quadrivalent HPV vaccine effectiveness and impact on cervical/cervicovaginal, anal, and oral HPV infections, anogenital warts, lesions in anus, cervix, oropharynx, penis, vagina or vulva, and recurrent respiratory papillomatosis.

EXPERT OPINION

The rapid growth in access to real-world data allows global monitoring of effects of different public health interventions, including HPV vaccination programs. But the use of data which are not collected or organized to support research also underscore a need to develop robust methodology that provides insight of vaccine effects and consequences of different health policy decisions. To achieve the WHO elimination goal, we foresee a growing need to evaluate HPV vaccination programs globally. A critical appraisal summary of methodology used will provide timely guidance to researchers who want to initiate research activities in various settings.

Cost-effectiveness of Interventions to Increase HPV Vaccine Uptake

OBJECTIVES

We sought to prioritize interventions for increasing human papillomavirus (HPV) vaccination coverage based on cost-effectiveness from a US state perspective to inform decisions by policy makers.

METHODS

We developed a dynamic simulation model of HPV transmission and progression scaled to a medium-sized US state (5 million individuals). We modeled outcomes over 50 years comparing no intervention to a one-year implementation of centralized reminder and recall for HPV vaccination, school-located HPV vaccination, or quality improvement (QI) visits to primary care clinics. We used probabilistic sensitivity analysis to assess a range of plausible outcomes associated with each intervention. Cost-effectiveness was evaluated relative to a conservative willingness-to-pay threshold; $50 000 per quality-adjusted life-year (QALY) .

RESULTS

All interventions were cost-effective, relative to no intervention. QI visits had the lowest cost and cost per QALY gained ($1538 versus no intervention). Statewide implementation of centralized reminder and recall cost $28 289 per QALY gained versus QI visits. School-located vaccination had the highest cost but was cost-effective at $18 337 per QALY gained versus QI visits. Scaling to the US population, interventions could avert 3000 to 14 000 future HPV cancers. When varying intervention cost and impact over feasible ranges, interventions were typically preferred to no intervention, but cost-effectiveness varied between intervention strategies.

CONCLUSIONS

Three interventions for increasing HPV vaccine coverage were cost-effective and offered substantial health benefits. Policy makers seeking to increase HPV vaccination should, at minimum, dedicate additional funding for QI visits, which are consistently effective at low cost and may additionally consider more resource-intensive interventions (reminder and recall or school-located vaccination).

One-Dose Human Papillomavirus Vaccination and the Risk of Genital Warts: A Danish Nationwide Population-based Study

BACKGROUND

Increasing evidence suggests that 1-dose human papillomavirus (HPV) vaccination may protect significantly against HPV-related disease. We provide nationwide, real-world data on the risk of genital warts (GWs) after <3 vaccine doses.

METHODS

All Danish women born in 1985-2003 were identified, and individual-level vaccination data were retrieved. The cohort was followed up for first occurrence of GWs until 31 December 2016. Using Poisson regression, we calculated incidence rates (IRs) of GWs per 100 000 person-years and IR ratios (IRRs) with corresponding 95% confidence intervals (CIs) for GWs, according to vaccination status, age at first dose, and calendar time.

RESULTS

The cohort comprised 1 076 945 girls and women, of whom 485 408 were vaccinated. For girls initiating vaccination at age 12-14 years and 15-16 years, 1-dose vaccine effectiveness (VE) was 71% (IRR = 0.29; 95% CI, .22-.38) and 62% (0.38; .29-.49), respectively, compared with unvaccinated girls. In the same age groups, 2-dose VE was 78% (IRR, 0.22; 95% CI, .18-.26) and 68% (0.32; .26-.38), respectively. After 2009, the IRRs for 3 versus 1 dose and 2 versus 1 dose increased towards unity over calendar time, being 0.69 (95% CI, .57-.84) and 0.86 (.68-1.08) in 2016, respectively.

CONCLUSIONS

In this study, 1 or 2 doses of quadrivalent HPV vaccine was associated with substantial protection against GWs in girls vaccinated at age ≤16 years. The 1-dose VE approached that of 3 or 2 doses over calendar time, probably reflecting the impact of herd protection.

Human Papillomavirus Vaccination and Anogenital Warts: A Systematic Review of Impact and Effectiveness in the United States

BACKGROUND

Assessing the impact and effectiveness of HPV vaccines on anogenital warts in the United States can provide early indication of the success of vaccination programs as well as identify potential areas for improvement.

METHODS

Articles were identified from the PubMed, Medline, and Embase databases. Exclusion criteria were applied, and remaining studies were then classified as impact or effectiveness studies.

RESULTS

Eight eligible studies published through March 2018 were included. Population-based impact studies examining trends in diagnoses reported consistent declines in females ages 25 years and younger after 2006 when routine female vaccination began in the United States. Declines in males ages 25 years and younger were also seen; however, these declines were lower than those in females and more evident after routine male vaccination began in 2011. Among females and males older than 25 years, little to no change has been seen in the trends of anogenital warts since 2006. Studies that included the pre-vaccine era (before 2006) reported increasing trends during this period. After vaccine introduction, a reversal in these trends was observed. Effectiveness studies that included individual-level vaccination histories consistently demonstrated a lower risk of anogenital warts for those receiving at least one dose of the vaccine compared to those unvaccinated.

CONCLUSIONS

These findings suggest that the degree of HPV vaccine impact has varied substantially by age and sex. Achieving the full prevention potential of HPV vaccines will likely require greater coverage among both females and males. Post-licensure estimates of effectiveness demonstrate the real-world benefit of the vaccine.

Human Papillomavirus Vaccine Effectiveness Against HPV Infection: Evaluation of One, Two, and Three Doses

Background

Highly effective human papillomavirus (HPV) vaccines are used in many national programs in 3- or 2-dose schedules. We examined HPV vaccine effectiveness against HPV prevalence by number of doses.

Methods

We collected residual liquid-based cytology samples from US women aged 20–29 years who were screened for cervical cancer. Women continuously enrolled from 2006 through the specimen collection date were analyzed. Specimens were tested using the Linear Array assay. We analyzed prevalence of quadrivalent HPV vaccine (4vHPV) types (HPV 6,11,16,18) and other HPV-type categories and determined prevalence ratios (PRs) and 95% confidence intervals (CIs) for 1, 2, and 3 compared with no vaccine doses.

Results

Among 4269 women, 1052 (24.6%) were unvaccinated, 2610 (61.1%) received 3 doses, 304 (7.1%) received 2 doses, and 303 (7.1%) received 1 dose. The 4vHPV-type prevalence was 7.4% among unvaccinated women compared with 1.7%, 1.0%, and 1.0% among 1-, 2-, and 3-dose recipients. Among women vaccinated at ≤18 years, adjusted PRs for 1, 2, and 3 doses were 0.06 (95% CI, 0.01–0.42), 0.05 (95% CI, 0.01–0.39), and 0.06 (95% CI, 0.04–0.12).

Conclusions

Among women who received their first dose at age ≤18, estimated HPV vaccine effectiveness was high regardless of number of doses.

Addressing HPV vaccine myths: practical information for healthcare providers

Human papillomavirus (HPV) vaccine uptake consistently lags behind that of other adolescent vaccines. In 2017, uptake of a single HPV vaccine dose and HPV vaccine series completion was 66% and 49%, respectively, compared to uptake of tetanus, diphtheria, and acellular pertussis vaccine (89%) and quadrivalent meningococcal conjugate vaccine (85%). Reasons for not vaccinating adolescents again HPV are varied, and in many cases, are rooted in commonly spread myths and misperceptions about the vaccine. In this review, we address five key myths - HPV vaccination is not effective at preventing cancer; Pap smears are sufficient to prevent cervical cancer; HPV vaccination is not safe; HPV vaccination is not needed since most infections are naturally cleared by the immune system; 11-12 years of age is too young to vaccinate. For each myth, we summarize the scientific evidence refuting the myth and provide speaking prompts for healthcare professionals to communicate about HPV vaccination.

Persistence of immune response following bivalent HPV vaccination: A follow-up study among girls routinely vaccinated with a two-dose schedule

BACKGROUND

In this cohort study, we examined antibody levels and avidity after a two-dose schedule (0, 6 months) of the bivalent HPV-vaccine in girls routinely vaccinated in the Dutch HPV-vaccination program, up to 2 years following vaccination.

METHODS

A blood sample at 7, 12 and 24 months after the first dose and questionnaire data were collected (n = 56). HPV type-specific antibody concentrations (lU/ml) against seven types (HPV16/18/31/33/45/52/58) were assessed using a validated virus-like particles (VLP) multiplex immunoassay. Avidity was tested using a modification of this assay.

RESULTS

Seropositivity for vaccine types HPV 16 and 18 was 100% up to month 24, but declined for HPV-types 31/33/45/52/58, although not statistically significant for HPV45. All Geometric Mean Concentrations (GMCs) declined by months 12 and 24, but remained high for HPV16/18. Between month 7 and 12, GMCs declined more for other types. High avidity antibodies were induced up to 24 months for vaccine types (75%, 76-78% and 81-82% at months 7, 12 and 24, respectively), but for other types antibody avidity was 16-29% at month 7, 20-32% at month 12 and 19-32% at month 24.

CONCLUSIONS

GMCs declined over time for HPV-types 16/18/31/33/45/52/58, but remained high for vaccine-types HPV16/18 up to 24 months of follow-up. Antibody avidity was >75% for vaccine types but <35% for other HPV-types. Further follow-up of this cohort will provide insight into antibody and avidity kinetics over time.

Human papillomavirus vaccine effectiveness by number of doses: Systematic review of data from national immunization programs

BACKGROUND

Human papillomavirus (HPV) vaccines were first licensed as a three-dose series; a two-dose series is now recommended in some age groups and there is interest in possible one-dose vaccination.

METHODS

We conducted a systematic literature review of HPV vaccine effectiveness by number of doses, including assessment of biases and impact of varying buffer periods (time between vaccination and outcome counting).

RESULTS

Of 3787 articles identified, 26 full articles were assessed and 14 included in our review. All studies were conducted within the context of recommended three-dose schedules of bivalent (3) or quadrivalent HPV vaccine (11). Two evaluated effectiveness for prevention of HPV prevalence, six anogenital warts, and six abnormal cervical cytology or histology. Many studies found differences between three-, two- and one-dose vaccine recipients, indicating possible differences in HPV exposure prior to vaccination or in risk behavior. Adjusted or stratified analyses were conducted to control for potential confounding. All studies found significant vaccine effectiveness with three doses, 11 with two doses at various intervals, and six with one dose. Most studies showed a relationship (not always statistically significant) between effectiveness and number of doses, with greater decreases in HPV-related outcomes with three, followed by two and one dose(s). Few studies conducted formal comparisons of three vs fewer doses. Three of four studies that examined buffer periods found higher effectiveness and a smaller difference by number of doses with longer periods.

CONCLUSION

Most post-licensure studies report highest effectiveness with three doses; some found no statistically significant difference between two and three doses. Additionally, almost half found some effectiveness with one dose. Several biases impact estimates, with most biasing two- and one-dose results away from showing effectiveness. Future effectiveness studies, examining persons vaccinated prior to sexual activity and using methods to reduce potential sources of bias, can help inform vaccination policy.

Population-based HPV vaccination programmes are safe and effective: 2017 update and the impetus for achieving better global coverage

Persistent oncogenic human papillomavirus (HPV) is the cause of cervical cancer, as well as cancers of the anus, penis, vulva, vagina and oropharynx. There is good evidence that prophylactic HPV vaccines are immunogenic and effective against targeted-type HPV infections and type-specific genital lesions, including high-grade cervical intraepithelial neoplasia (CIN), when administered prior to HPV infection. There is good evidence that HPV vaccines are safe in population usage, with the most frequent adverse event being injection-site reactions. There is evidence to support some cross-protection against non-targeted types occurring following the administration of HPV vaccines. There is limited evidence suggesting that HPV vaccines may be beneficial in preventing future disease in women treated for high-grade CIN. This chapter focuses on the accumulated evidence regarding the global use of the three licensed HPV vaccines including safety, immunogenicity, duration of protection, effectiveness, coverage to date and barriers to higher coverage.