Impact of Human Papillomavirus Vaccination, Rwanda and Bhutan

Concentration strategies for spiked and naturally present biomarkers in non-invasively collected first-void urine

BACKGROUND

First-void urine (FVU) provides a non-invasive method for collecting a wide range of biomarkers found in genital tract secretions. To optimize biomarker collection in FVU, this study investigated the impact of naturally present and supplemented precipitating agents: uromodulin (UMOD) and polyethylene glycol (PEG), on the concentration of human papillomavirus (HPV) pseudovirions (PsV), cell-free DNA (cfDNA), and cellular genomic DNA (gDNA) through centrifugation.

METHODS

FVU samples from ten healthy female volunteers, along with a control sample, were spiked with seal herpesvirus 1 (PhHV-1) DNA, HPV16 plasmid DNA, and HPV16 PsV with an enhanced green fluorescent protein (EGFP) reporter. The samples were subjected to various concentration protocols involving PEG precipitation, low-speed centrifugation (5 min at 1000×g), and medium-speed centrifugation (1 h at 3000×g). Subsequently, quantitative PCR (qPCR) was used to assess cellular and cell-free glyceraldehyde-3-phosphate dehydrogenase (GAPDH) DNA, cell-free PhHV-1 and HPV16 DNA, and PsV (EGFP) DNA. In addition, UMOD levels were measured.

RESULTS

The findings revealed that PEG significantly increased the concentration of cfDNA and gDNA in the pellet after centrifugation, with the most pronounced effect observed for cfDNA. Moreover, low-speed centrifugation without PEG effectively depleted cellular gDNA while preserving cfDNA in the supernatants. Pseudovirions were consistently pelleted, even with low-speed centrifugation, and a positive but not significant effect of PEG on PsV (EGFP) DNA yield in the pellet was observed. Additionally, a significant correlation was observed between UMOD and GAPDH, HPV16, and PsV (EGFP) DNA quantities in the pellet. Furthermore, large variations among the FVU samples were observed.

CONCLUSIONS

With this study, we provide novel insights into how various biomarker precipitation protocols, including both the properties of FVU and the use of PEG as a precipitating agent, influence the concentration of cfDNA, cellular gDNA, and pseudovirions.

Understanding Factors Contributing to Vaccine Hesitancy in a Large Metropolitan Area

Vaccine hesitancy has become a major global concern, leading to a significant decrease in the vaccination rate, with the World Health Organization recognizing it as one of the top ten threats to public health. Moreover, the health cost generated is evaluated to be 27 billion dollars per year in the US alone. To investigate the association between demographic variables and knowledge, attitudes, and behaviours related to vaccination, a survey-based cross-sectional study was conducted with 1163 individuals. Three models were used to perform a multiple linear regression analysis. In Model I, knowledge about vaccinations was found to be associated with smoking habits, education, and marital status. In Model II, attitudes towards vaccinations were significantly associated with sex, smoking habits, education, marital status, and knowledge. In Model III, behaviours related to vaccination were associated with sex, smoking habits, having children, knowledge, and attitudes. One potential solution to improve behaviours related to vaccinations in the general population is to implement specific public health programs, which can be a cost-effective intervention. This study provides valuable insights into the determinants of knowledge, attitudes, and behaviours related to vaccinations in the general population.

Follow-up of humoral immune response after HPV vaccination using first-void urine: A longitudinal cohort study

Assessment of humoral immune responses following human papillomavirus (HPV) vaccination currently relies on invasive blood sampling. This longitudinal cohort study explores the usability of first-void urine as a noninvasive alternative sample for antibody detection. In this study, 58 women receiving three doses of the 9vHPV vaccine within a Gardasil9 (9vHPV) Phase III randomized controlled trial were included. Participants provided paired first-void urine and blood samples before vaccination (M0), 1 month after the third dose (M7), and ~3 years after the third dose (M43). Type-specific antibody responses to the 9vHPV types were analyzed in 174 first-void urine and 172 serum samples using a virus-like particle-based IgG multiplex enzyme-linked immunosorbent assay. Additionally, total human IgG concentrations were determined using the BioPlex assay. At M7, 1 month after complete 9vHPV vaccination, 95%-100% of first-void urine and 100% of serum samples had detectable concentrations, varying by HPV type. At M43, 84%-100% of first-void urine and 98%-100% of serum samples had HPV-specific antibody concentrations. Results show significant Spearman rank correlations between type-specific HPV-antibody concentrations for paired first-void urine and serum at all time points. This study confirms the potential feasibility of utilizing first-void urine as a noninvasive immunological sample within HPV vaccine trials.

Testing for Human Papillomaviruses in Urine, Blood, and Oral Specimens: an Update for the Laboratory

Twelve high-risk alpha human papillomavirus (HPV) genotypes cause approximately 690,000 cancer cases annually, with cervical and oropharyngeal cancer being the two most prominent types. HPV testing is performed in laboratory settings for various applications of a clinical, epidemiological, and research nature using a range of clinical specimens collected by clinicians or by individuals (self-collected specimens). Here, we reflect on the importance and justification of using the right test for the right application and provide practical updates for laboratories either participating in or anticipating involvement in HPV testing in three specimen types, namely, urine, blood, and oral specimens, which are considered "alternative" specimens by many. In addition to clinician-collected cervical samples and self-collected cervicovaginal samples, first-void urine is emerging as a credible specimen for HPV-based cervical cancer screening, triage of HPV screen-positive women, monitoring HPV vaccine impact, and HPV testing in groups for which a less invasive sample is preferred. Detection of cell-free DNA (including HPV DNA) in blood has great promise for the early detection of HPV-attributable oropharyngeal cancer (HPV-AOC) and potentially other HPV-driven cancers and as an adjunct prognostic marker in long-term tumor surveillance, including treatment response. The moderate sensitivity of HPV testing in oral rinses or swabs at HPV-AOC diagnosis prevents its use in HPV-AOC secondary prevention but represents a promising prognostic tool in HPV-AOC tertiary prevention, where the HPV persistence in oral rinses throughout treatment may predict early HPV-AOC recurrences and/or the development of secondary HPV-AOC. The increasing sophistication of specific collection devices designed for alternative samples and the enhanced precision of novel molecular technologies are likely to support the evolution of this field and catalyze potential translation into routine practice.

Human papillomavirus vaccine effect against human papillomavirus infection in Rwanda: evidence from repeated cross-sectional cervical-cell-based surveys

BACKGROUND

Rwanda was the first African country to implement national human papillomavirus (HPV) vaccination (against types HPV6, 11, 16, and 18). In 2011, a school-based catch-up programme was initiated to vaccinate girls aged younger than 15 years but it also reached older girls in schools. We aimed to estimate the population-level effect of HPV vaccination on HPV prevalence.

METHODS

Cross-sectional surveys were done between July, 2013, and April, 2014 (baseline), and between March, 2019, and December, 2020 (repeat), in sexually active women aged 17-29 years at health centres in the Nyarugenge District of Kigali, Rwanda. HPV prevalence was assessed in cervical cell samples collected by a health-care worker in PreservCyt solution (Cytyc, Boxbourough, MA, USA) and tested using a general primer (GP5+ or GP6+)-mediated PCR. Adjusted overall, total, and indirect (herd immunity) vaccine effectiveness was computed as the percentage of HPV detection among all women and among unvaccinated women.

FINDINGS

1501 participants completed the baseline survey and 1639 completed the repeat survey. HPV vaccine-type prevalence in participants aged 17-29 years decreased from 12% (173 of 1501) in the baseline survey to 5% (89 of 1639) in the repeat survey, with an adjusted overall vaccine effectiveness of 47% (95% CI 31 to 60) and an adjusted indirect vaccine effectiveness of 32% (9 to 49). Among participants aged 17-23 years, who were eligible for catch-up vaccination, the adjusted overall vaccine effectiveness was 52% (35 to 65) and the adjusted indirect vaccine effectiveness was 36% (8 to 55), with important heterogeneity according to education (overall vaccine effectiveness was 68% [51 to 79] in participants with ≥6 years of school completed and 16% [-34 to 47] in those with <6 years) and HIV status (overall vaccine effectiveness was 55% [36 to 69] for HIV-negative participants and 24% [-62 to 64] for HIV-positive participants).

INTERPRETATION

In Rwanda, the prevalence of vaccine-targeted HPV types has been significantly decreased by the HPV vaccine programme, most notably in women who were attending school during the catch-up programme in 2011. HPV vaccine coverage and population-level impact is expected to increase in future cohorts who are eligible for routine HPV vaccination at age 12 years.

FUNDING

Bill & Melinda Gates Foundation.

High-risk human papillomavirus genotype distribution among women living with HIV; implication for cervical cancer prevention in a resource limited setting

BACKGROUND

For women living with HIV (WLHIV), the burden of persistent HPV infection, cervical pre-cancerous lesions and cancer have been demonstrated to be higher than among HIV-negative women. As Ghana and other lower-middle-income countries (LMIC) work toward developing national cervical cancer programmes, it is essential that local scientific evidence be provided to guide policy decisions, especially for such special populations. The objective of this study was to determine the distribution of high-risk HPV genotype and related factors among WLHIV and its implication for the prevention of cervical cancer prevention efforts.

METHODS

A cross-sectional study was conducted at the Cape Coast Teaching Hospital in Ghana. WLHIV, aged 25-65 years, who met the eligibility criteria were recruited through a simple random sampling method. An interviewer-administered questionnaire was used to gather socio-demographic, behavioural, clinical and other pertinent information. The AmpFire HPV detection system (Atila BioSystem, Mointain View, CA was used to detect 15 high-risk HPV genotypes from self-collected cervico-vaginal samples. The data collected were exported to STATA 16.0 for statistical analysis.

RESULTS

In all, 330 study participants, with mean age of 47.2 years (SD ± 10.7), were involved. Most (69.1%, n = 188/272) had HIV viral loads < 1000 copies/ml and 41.2% (n = 136) had ever heard of cervical screening. The overall hr-HPV prevalence was 42.7% (n = 141, 95% CI 37.4-48.1) and the five commonest hr-HPV types among screen positives were HPV59 (50.4%), HPV18 (30.5%), HPV35 (26.2%), HPV58 (17%) and HPV45 (14.9%). Most infected women (60.3%, n = 85) had multiple hr-HPV infections, with about 57.4% (n = 81) having 2-5 h-HPV types, while 2.8% (n = 4) had more than five hr-HPV types. A total of 37.6% (n = 53) had HPV16 and/or18, while 66.0% (n = 93) had the hr-HPV genotypes covered by the nonavalent vaccine. Women with HIV viral load ≥ 1000copies/ml (AOR = 5.58, 95% CI 2.89-10.78, p < 0.001) had a higher likelihood of being co-infected.

CONCLUSION

This study found out that the prevalence of hr-HPV still remains high in women with HIV, with a notable occurrence of multiple infections and infection with genotypes 16 and/or18. Additionally, an association was established between hr-HPV and infection HIV viral load.. Therefore, comprehensive HIV care for these women should include awareness of cervical cancer, consideration of vaccination and implementation of screening and follow-up protocols. National programmes in LMIC, such as Ghana, should consider using HPV-based screen-triage-treat approach with partial genotyping.

Human papillomavirus vaccination in low- and middle-income countries: progression, barriers, and future prospective

Human papillomavirus (HPV) is a viral infection that, if does not go away, can cause health problems like genital warts and cancer. The national immunization schedules for individuals before sexual debut, significantly decreased HPV-associated mortality and it will be affordable. However, immunization programs remain vulnerable to macroeconomic factors such as inflation, fiscal policy, employment levels, and national income. This review aims to investigate the association between national income in lower-middle-income countries to explore recent advances and potential issues, as well as how to deal with challenges.

Which is the best management for women with normal cervical cytologic findings despite positivity for non-16/18 high risk human papillomaviruses?

Women who test positive for the human papillomavirus (HPV) but have normal cytology constitute the predominant subgroup of patients in the screening population in the post-vaccination era. The distribution of HPV genotypes changed dramatically, which was attributable to an increase in HPV vaccination coverage. These changes have created uncertainty about how to properly manage women with normal cytology, non-HPV16/18 infections, or persistent infections. Current recommendations include retesting and continued surveillance in the absence of HPV16/18 infection. However, these are not always applicable. The ability to implement genotyping or incorporate HPV16/18 with some additional high-risk HPV (HR-HPV) types for triage and management with the aim of identifying type-specific risks in this population could be acceptable. When the next set of guidelines is updated, generating potential triage strategies for detecting high-grade cervical lesions, such as the p16/Ki67 cytology assay and other alternatives that incorporate genotyping with newer tests, should be considered. Current clinical management is shifting to risk-based strategies; however, no specific risk threshold has been established in this population. Importantly, innovative triage testing should be evaluated in combination with primary screening and management. Furthermore, there is an untapped opportunity to coordinate HPV genotyping in combination with colposcopic characteristics to modify risk in this group. Hence, providing a more personalized schedule through the efficient application of risk stratification and improving the detection of pre-cancer and cancer is an option worth exploring.

Human Papillomavirus Vaccine Impact and Effectiveness Through 12 Years After Vaccine Introduction in the United States, 2003 to 2018

BACKGROUND

Human papillomavirus (HPV) vaccination was introduced in 2006 for females and in 2011 for males.

OBJECTIVE

To estimate vaccine impact and effectiveness against quadrivalent HPV vaccine (4vHPV)-type prevalent infection among sexually experienced U.S. females and vaccine effectiveness for sexually experienced U.S. males.

DESIGN

NHANES (National Health and Nutrition Examination Survey) conducted in 2003 to 2006 (prevaccine era) and in 2007 to 2010, 2011 to 2014, and 2015 to 2018 (vaccine eras).

SETTING

Nationally representative U.S. surveys.

PARTICIPANTS

Sexually experienced participants aged 14 to 24 years.

INTERVENTION

U.S. HPV vaccination program.

MEASUREMENTS

Participant-collected cervicovaginal and penile specimens were tested for HPV DNA. The prevalences of 4vHPV and non-4vHPV types were estimated in each era for females and in 2013 to 2016 for males. Prevalences among the female population overall, vaccinated females, and unvaccinated females were compared in vaccine eras versus the prevaccine era (vaccine impact). Within each vaccine era, prevalence among vaccinated females was compared with that among unvaccinated females (vaccine effectiveness). Vaccine impact and effectiveness were estimated as (1 - prevalence ratio) · 100.

RESULTS

Among sexually experienced females aged 14 to 24 years, the impact on 4vHPV-type prevalence in 2015 to 2018 was 85% overall, 90% among vaccinated females, and 74% among unvaccinated females. No significant declines were found in non-4vHPV-type prevalence. Vaccine effectiveness ranged from 60% to 84% during vaccine eras for females and was 51% during 2013 to 2016 for males.

LIMITATION

Self- or parent-reported vaccination history and small numbers in certain subgroups limited precision.

CONCLUSION

Nationally representative data show increasing impact of the vaccination program and herd protection. Vaccine effectiveness estimates will be increasingly affected by herd effects.

PRIMARY FUNDING SOURCE

Centers for Disease Control and Prevention.

The potential of urine for human papillomavirus-related cervical cancer prevention

Cervical cancer is one of the most preventable cancers. The introduction of human papillomavirus (HPV) vaccines and the adaptation of regular screening programs are key actions that need to be generalized globally to achieve the goal of cervical cancer elimination. However, it is still challenging to achieve satisfactory coverage rate, and many women are reluctant to participate in gynecologic examination. In this article, we review the research on the application of HPV detection in urine samples for cervical cancer screening and vaccine monitoring, as well as discuss the technical challenges and new technological advancements in urine-based tests. HPV detection in urine is an excellent noninvasive alternative that is widely accepted by women, relatively affordable, and provides the potential to reach women without the necessity for clinical visits. Thus, it is an attractive tool for both cervical cancer screening and vaccine monitoring.

Human papillomavirus prevalence in male and female university students in Gaborone, Botswana

In 2015, Botswana introduced the quadrivalent human papillomavirus (HPV) vaccine as a two-dose schedule in girls aged 9–13 years. We sought to establish a baseline HPV prevalence in unvaccinated young adults in Botswana. HIV-uninfected men and women aged 18–22 years were recruited from the University of Botswana in Gaborone during October 2019–February 2021. Demographic and behavioural characteristics were self-reported during structured interviews. Self-collected vaginal and penile swabs were tested for 28 HPV types using Seegene Anyplex II HPV28. We compared any HPV type, quadrivalent vaccine (HPV 6, 11, 16, 18)-type and non-quadrivalent vaccine-type prevalence in men and women and evaluated the risk factors for prevalence of any HPV type. A total of 493 men and 500 women were included in the analysis. Compared to men, women had higher prevalence of any HPV type (63.0% versus 31.4%, P < 0.001), vaccine-type HPV (21% versus 9.7%, P < 0.001) and non-vaccine-type HPV (60.4% versus 28.4%, P < 0.001). Higher prevalence of any HPV type in men and women was associated with having ≥2 sex partners in the past 12 months; always using condoms in the past 3 months was associated with a lower HPV prevalence. These data provide baseline information for future evaluation of the population impact of the HPV vaccination programme, including potential herd effects in men.

Preventing Cervical Cancer Globally: Are We Making Progress?

An unacceptable number of women continue to die from cervical cancer around the world each year. Despite established primary and secondary prevention measures, and a natural history of disease which provides a long latent phase in which to intervene, there are still more than 500,000 women diagnosed with cervical cancer globally each year, and 300,000 related deaths. Approximately 90% of these cervical cancer cases and deaths occur in low- and middle-income countries (LMIC). The World Health Organization (WHO) recently launched a Global Strategy to Accelerate the Elimination of Cervical Cancer that outlines 3 key steps: (i) vaccination against human papillomavirus (HPV); (ii) cervical screening; and (iii) treatment of precancerous lesions and management of invasive cancer. Successful implementation of all 3 steps could reduce more than 40% of new cervical cancer cases and 5 million related deaths by 2050. However, this initiative requires high level commitment to HPV immunization programs, innovative approaches to screening, and strengthening of health systems to provide treatment for both precancerous lesions as well as invasive cervical cancer.

Epidemiology of HPV Related Malignancies

Human papillomavirus is the most common sexually transmitted infection in the world and had been linked to both anogenital and oropharyngeal cancers. It causes nearly 100% of cervical cancers and an increasing portion of oropharyngeal cancers. The geographical burden of cervical HPV infection and associated cancers is not uniform and is mainly found in low middle income countries in South America, Africa, and Asia. However, HPV-positive oropharyngeal cancer is rapidly becoming more prevalent in high middle income countries. With the development of vaccines which prevent HPV infection, the World Health Organization has designated the extirpation of HPV and its associated cancers a priority. Countries that have implemented adequate vaccine programs have shown a decrease in HPV prevalence. Understanding the epidemiology of HPV and its associated cancers is fundamental in improving vaccine programs and other health programs.

Global estimates of expected and preventable cervical cancers among girls born between 2005 and 2014: a birth cohort analysis

BACKGROUND

WHO has launched an initiative aiming to eliminate cervical cancer as a public health problem. Elimination is a long-term target that needs long-lasting commitment. To support local authorities in implementing human papillomavirus (HPV) vaccination, we provide regional and country-specific estimates of cervical cancer burden and the projected impact of HPV vaccination among today's young girls who could develop cervical cancer if not vaccinated.

METHODS

The expected number of cervical cancer cases in the absence of vaccination among girls born between 2005 and 2014 was quantified by combining age-specific incidence rates from GLOBOCAN 2018 and cohort-specific mortality rates by age from UN demographic projections. Preventable cancers were estimated on the basis of HPV prevalence reduction attributable to vaccination and the relative contribution of each HPV type to cervical cancer incidence. We assessed the number of cervical cancer cases preventable through vaccines targeting HPV types 16 and 18, with and without cross-protection, and through vaccines targeting HPV types 16, 18, 31, 33, 45, 52, and 58.

FINDINGS

Globally, without vaccination, the burden of cervical cancer in these birth cohorts is expected to reach 11·6 million (95% uncertainty interval 11·4-12·0) cases by 2094. Approximately 75% of the burden will be concentrated in 25 countries mostly located in Africa and Asia, where the future number of cases is expected to increase manyfold, reaching 5·6 million (5·4-6·0) cases in Africa and 4·5 million (4·4-4·6) cases in Asia. Worldwide immunisation with an HPV vaccine targeted to HPV types 16 and 18, with cross-protection against HPV types 31, 33, and 45, could prevent about 8·7 million (8·5-9·0) cases.

INTERPRETATION

Detailed estimates of the increasing burden of cervical cancer and projected impact of HPV vaccination is of immediate relevance to public health decision makers. Shifting the focus of projections towards recently born girls who could develop cervical cancer if not vaccinated is fundamental to overcome stakeholders' hesitancy towards HPV vaccination.

FUNDING

Bill & Melinda Gates Foundation, Canadian Institutes of Health Research.

Current understandings of the impact of mandatory vaccination laws in Europe

Vaccinations are among the most successful preventive tools to protect collective health. In response to alarming vaccines preventable diseases (VPDs) outbreaks resurgence, decreased vaccination coverage and vaccine refusal, several European countries have recently revised their vaccination policies introducing or extending mandatory vaccinations. This review examines the health, political and ethical aspects of mandatory vaccination.The authors first clarify terms and definitions and propose a conceptual framework of mandatory policies. Second, they describe the current status of mandatory childhood immunization programmes in Europe, assessing selected mandatory laws. Third, as the authors conduct a systematic review of the literature (retrieving from Medline 17 relevant records between 2010 and 2020), they take an analytical approach to measure the impact of mandatory vaccination policies on both VPDs control and immunization coverage, but also on population attitudes toward vaccines. 40% of European countries currently have mandatory vaccination policies; however, policies vary widely and, although there is evidence of increased vaccine uptake, their impact on informed adherence to preventive behaviors is scant.Although mandatory vaccination policies might be needed to protect collective health in times of emergency, public health goals of VPD prevention and health promotion should primarily be pursued through health education and population empowerment.

Surveillance systems for monitoring cervical cancer elimination efforts: Focus on HPV infection, cervical dysplasia, cervical screening and treatment

In order to achieve the global elimination of cervical cancer as a public health problem, close surveillance of progress in public health and clinical activities and outcomes across the three pillars of vaccination, screening and treatment will be required. Surveillance should ideally occur within an integrated system that is planned, funded, and regularly evaluated to ensure it is providing timely, accurate and relevant feedback for action. In this paper, we conceptualise the main public health surveillance objectives as process and outcome measures in each of the three pillars. Process measures include coverage/participation measures for vaccination, screening and treatment alongside the ongoing assessment of the quality and reach of these programs and activities. Outcome measures related to the natural history of human papillomavirus (HPV) infection include HPV infection prevalence, precursor cervical lesions and cervical cancers (including stage at diagnosis, cancer incidence and mortality). These outcome measures can be used for monitoring the effectiveness of the three core activities in the short, medium and long term to assess whether these interventions are effectively reducing their occurrence. We discuss possible methods for the surveillance of these measures in the context of country capacity, drawing from examples in Australia, the USA and in low and middle income countries.

Human papillomavirus vaccine coverage in Rwanda: A population-level analysis by birth cohort

BACKGROUND

In 2011, Rwanda became the first African nation to implement a national human papillomavirus (HPV) vaccination program, conceived to protect girls aged <15 years (i.e. born ≥1997). After an initial school-grade-targeted catch-up campaign, there was a transition to routine vaccination of 12 year-olds only. We aimed to produce population-level vaccine coverage estimates.

METHODS

The Rwandan Expanded Program on Immunization (EPI) collected data on number of eligible girls and HPV vaccines delivered, stratified by calendar year (2011-2018), girl's age, district and vaccination round. HPV vaccine coverage was estimated by birth cohort (reconstituted using calendar year and age), as a proportion of (1) eligible target, and (2) the 2012 Rwandan census population.

RESULTS

1,156,863 girls received first dose of HPV vaccine between 2011 and 2018, corresponding to 98% of the eligible target. Median vaccination age was 15 years (interquartile range [IQR] 13-16) in 2011-2013 (school grade-targeted catch-up), 13 years (IQR 12-14) in 2014 (transition) and 12 years in 2015-2018 (routine). Population-level coverage versus the census increased from 10 to 40% for girls born in 1993-1995 (median vaccination age = 17 years) to 50-65% for 1996-2000 birth cohorts (14 years), and 80-90% for 2001-2006 birth cohorts (12 years). Coverage trends were similar across provinces and in the capital, Kigali. Second and third round coverage suggested most vaccinated girls completed their recommended dosing regimen (which reduced from 3 to 2 doses in 2015).

CONCLUSIONS

Birth cohorts provide a clear picture of population-level HPV vaccine coverage after a pragmatic catch-up campaign, particularly in Rwanda where eligible school grades included wide age ranges. Whilst the catch-up campaign resulted in some coverage gaps in out-of-school teenagers, coverage remains high in cohorts routinely targeted as 12 year-olds.