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Human papillomavirus and related disease in underage children : implications for prevention

Mireille Merckx (UGent)
(2014)
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Abstract
Infections with the human papillomavirus (HPV) constitute an important source of morbidity and mortality worldwide. HPV is implicated in a wide range of pathologies, and affects people of all ages and genders, including young children and adolescents. The overall objective of this study was to describe the genotype-specific prevalence of HPV infections in underage children (children and adolescents up to age 19), and investigate its evolution since the introduction of the prophylactic vaccine. Furthermore, this research project aimed to unravel the mechanism(s) of HPV infections at very young ages, i.e., the existence of vertical transmission of HPV from mother to child. The special needs of children and adolescents and their clinical management with respect to different issues was also investigated. The topic of research was the genital transmission of high-risk HPV types from mother to child. Knowledge of HPV in adults has been largely focused on sexual transmission. Data on infection in children are slowly becoming available. It is still a matter of debate to understand whether and how vertical transmission of HPV-positive mothers affects their children. A meta-analysis of published data was performed, including 20 studies or 3128 mother-child pairs. From the data, we found significant heterogeneity among different studies, and a relative risk increase of 33%. However, when the analysis was restricted to high-risk positive mothers only, the difference in risk was 45%. This is indicative for the existence of mother-to-child transmission of HPV, however it cannot confirm the causality. There is widespread acknowledgement that although adolescents share many characteristics with adults, their health-related problems and needs are different in a number of significant respects. Medical prevention of HPV infection in this population and clinical management of their needs has to be tailored. Our next study, focused on young adolescent women, revealed not only an unexpectedly high frequency of HPV infections in underage girls (15 to 19 years old); it also indicated that the genotyping profiles were somewhat different from what is commonly described for an adult population (19 to 25 years old). The top five high-risk genotypes most frequently observed in the younger population were HPV 16, HPV 51, HPV 66, HPV 31 and HPV 39, some of which are less frequent in the adult population (e.g. HPV39). The introduction of the HPV vaccine on the Belgian market (2007) offered new options for primary prevention of infection with HPV. Vaccination was offered on an opportunistic basis until 2009, when organized vaccination via school medicine was implemented. The early impact of this strategy is already evident in Belgium. We investigated the effects of this vaccination by considering the relative prevalence of HPV 16 and HPV 18 between 2009 and 2012. Very promising results since the vaccination became available were observed. There has been a significant reduction of HPV 16 (RR=0.61, 95%CI= 0.39-0.95) in girls up to 19 years old. A decline of HPV 18 prevalence could also be observed, albeit not as significant (RR=0.65, 95%CI= 0.29-1.48), probably due to the low prevalence of this genotype within the younger age category. For girls between 20 and 25 years of age, the HPV 16 positive testing was 7.5% (95% CI: 6.2% to 8.8%), and the prevalence for HPV 18 was 1.7% (95% CI: 1.1% to 2.4%). HPV prevalence did not change significantly; the trend was stable; this group has also been less vaccinated. Screening for cancer in youngsters is a debatable matter of cost effectiveness. According to current recommendations for prevention, women younger than 25 years old should not be screened regardless of the age of sexual initiation or other risk factors. A balance between benefits and harms must be found. Both cervical cytology and testing for high-risk types of HPV DNA can detect cervical cancer and its precursors, but each will detect many abnormalities that will not go on to become cancer. Annual screening with cytology alone has been shown to lead to a very small increase in cancers prevented but to greatly increase the number of unnecessary procedures and treatments. Extending the interval for screening strikes the most appropriate balance between benefits and harms. During this time period, young women are very likely to be exposed to HPV infection. All of this implies that the effect of a preventive vaccine on the prevalence of cervical cancer is clear. But prophylactic vaccines do not protect against infection (or malignancy) caused by other HPV types not contained in them, so cases of disease will still arise and require treatment. Faced with these limitations of preventive vaccines, the development of new preventive and therapeutic vaccines as effective tool to control the infection is mandatory. Our mission is to focus on disease control and prevention. We have to avoid possible hazards such as underestimating the risk of contamination and of changes in HPV type prevalence whereby what is oncogenic today might be of part of another typing tomorrow.

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Citation

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MLA
Merckx, Mireille. “Human Papillomavirus and Related Disease in Underage Children : Implications for Prevention.” 2014 : n. pag. Print.
APA
Merckx, Mireille. (2014). Human papillomavirus and related disease in underage children : implications for prevention. Ghent University. Faculty of Medicine and Health Sciences, Ghent, Belgium.
Chicago author-date
Merckx, Mireille. 2014. “Human Papillomavirus and Related Disease in Underage Children : Implications for Prevention”. Ghent, Belgium: Ghent University. Faculty of Medicine and Health Sciences.
Chicago author-date (all authors)
Merckx, Mireille. 2014. “Human Papillomavirus and Related Disease in Underage Children : Implications for Prevention”. Ghent, Belgium: Ghent University. Faculty of Medicine and Health Sciences.
Vancouver
1.
Merckx M. Human papillomavirus and related disease in underage children : implications for prevention. [Ghent, Belgium]: Ghent University. Faculty of Medicine and Health Sciences; 2014.
IEEE
[1]
M. Merckx, “Human papillomavirus and related disease in underage children : implications for prevention,” Ghent University. Faculty of Medicine and Health Sciences, Ghent, Belgium, 2014.
@phdthesis{5765590,
  abstract     = {Infections with the human papillomavirus (HPV) constitute an important source of morbidity and mortality worldwide. HPV is implicated in a wide range of pathologies, and affects people of all ages and genders, including young children and adolescents.
The overall objective of this study was to describe the genotype-specific prevalence of HPV infections in underage children (children and adolescents up to age 19), and investigate its evolution since the introduction of the prophylactic vaccine. Furthermore, this research project aimed to unravel the mechanism(s) of HPV infections at very young ages, i.e., the existence of vertical transmission of HPV from mother to child. The special needs of children and adolescents and their clinical management with respect to different issues was also investigated.
The topic of research was the genital transmission of high-risk HPV types from mother to child. Knowledge of HPV in adults has been largely focused on sexual transmission. Data on infection in children are slowly becoming available. It is still a matter of debate to understand whether and how vertical transmission of HPV-positive mothers affects their children. A meta-analysis of published data was performed, including 20 studies or 3128 mother-child pairs. From the data, we found significant heterogeneity among different studies, and a relative risk increase of 33%. However, when the analysis was restricted to high-risk positive mothers only, the difference in risk was 45%. This is indicative for the existence of mother-to-child transmission of HPV, however it cannot confirm the causality. There is widespread acknowledgement that although adolescents share many characteristics with adults, their health-related problems and needs are different in a number of significant respects. Medical prevention of HPV infection in this population and clinical management of their needs has to be tailored.
Our next study, focused on young adolescent women, revealed not only an unexpectedly high frequency of HPV infections in underage girls (15 to 19 years old); it also indicated that the genotyping profiles were somewhat different from what is commonly described for an adult population (19 to 25 years old). The top five high-risk genotypes most frequently observed in the younger population were HPV 16, HPV 51, HPV 66, HPV 31 and HPV 39, some of which are less frequent in the adult population (e.g. HPV39). The introduction of the HPV vaccine on the Belgian market (2007) offered new options for primary prevention of infection with HPV. Vaccination was offered on an opportunistic basis until 2009, when organized vaccination via school medicine was implemented. The early impact of this strategy is already evident in Belgium. We investigated the effects of this vaccination by considering the relative prevalence of HPV 16 and HPV 18 between 2009 and 2012. Very promising results since the vaccination became available were observed. There has been a significant reduction of HPV 16 (RR=0.61, 95%CI= 0.39-0.95) in girls up to 19 years old. A decline of HPV 18 prevalence could also be observed, albeit not as significant (RR=0.65, 95%CI= 0.29-1.48), probably due to the low prevalence of this genotype within the younger age category. For girls between 20 and 25 years of age, the HPV 16 positive testing was 7.5% (95% CI: 6.2% to 8.8%), and the prevalence for HPV 18 was 1.7% (95% CI: 1.1% to 2.4%). HPV prevalence did not change significantly; the trend was stable; this group has also been less vaccinated.
Screening for cancer in youngsters is a debatable matter of cost effectiveness. According to current recommendations for prevention, women younger than 25 years old should not be screened regardless of the age of sexual initiation or other risk factors. A balance between benefits and harms must be found. Both cervical cytology and testing for high-risk types of HPV DNA can detect cervical cancer and its precursors, but each will detect many abnormalities that will not go on to become cancer. Annual screening with cytology alone has been shown to lead to a very small increase in cancers prevented but to greatly increase the number of unnecessary procedures and treatments. Extending the interval for screening strikes the most appropriate balance between benefits and harms. During this time period, young women are very likely to be exposed to HPV infection. All of this implies that the effect of a preventive vaccine on the prevalence of cervical cancer is clear. But prophylactic vaccines do not protect against infection (or malignancy) caused by other HPV types not contained in them, so cases of disease will still arise and require treatment. Faced with these limitations of preventive vaccines, the development of new preventive and therapeutic vaccines as effective tool to control the infection is mandatory.
Our mission is to focus on disease control and prevention. We have to avoid possible hazards such as underestimating the risk of contamination and of changes in HPV type prevalence whereby what is oncogenic today might be of part of another typing tomorrow.},
  author       = {Merckx, Mireille},
  isbn         = {9789038224305},
  language     = {eng},
  pages        = {139},
  publisher    = {Ghent University. Faculty of Medicine and Health Sciences},
  school       = {Ghent University},
  title        = {Human papillomavirus and related disease in underage children : implications for prevention},
  year         = {2014},
}