The prevalence of human papillomavirus and bacterial vaginosis among young women in China: a cross-sectional study - BMC Women's Health - BMC Blogs Network

There are limited epidemiological data simultaneously evaluating the relationship between HPV prevalence and BV prevalence and their effect on cervical lesions among women aged 20–35 years in the Fujian province. In this study, the population aged 20–35 years, showed a relatively high HPV prevalence, but the rate of abnormal cervical lesions was low, which highlights the importance of HPV vaccines. In addition, a previous study suggested that the mortality rate of cervical cancer among young urban women increased by 4.1 percent per year in China, according to rough statistics [9]. However, current cervical cancer screening guidelines focus primarily on women older than 30 years. Therefore, the rate of missed cervical cancer diagnosis in young women under 30 years should receive more attention. According to our previous study [10], most women aged 20–35 years are willing to receive and pay for the HPV vaccine. Therefore, it is necessary to investigate the distribution of HPV and BV in women of this age group for the future application of cervical cancer vaccines in Fujian.

Several epidemiological studies have suggested a substantial difference in HPV prevalence and genotype distribution among different regions [11, 12], varying from 9.2% to 18.3%. In our study, the HPV prevalence rate was 16.2%, which is similar to the results of previous studies. However, the prevalence of HPV was 7.2% in Southeast Asia [13]. Compared with neighboring countries, the HPV prevalence rate in Fujian was higher, possibly because of the lack of HPV vaccine implementation and economic underdevelopment.

In our study, HPV-52 was the most common HR-HPV, consistent with the previous studies [14]. The next most frequent types were HPV-81, -68, -51 and -53. In other regions of China, the result was different. Ding et al. [14] suggested that the most common HPV genotypes were HPV-52, -16, -81, -58, and -18. A study in four large cities and four rural areas in China demonstrated HPV-16 to be the most common type, followed by HPV-58 and HPV-18 [15]. All of these data were based on a lifetime age range, and the age-specific data were limited. A study conducted by Li et al. [16] was performed among young women, but the study population was all from Western China. Recently, a study in Fujian province suggested that HPV-16, -52, -58, -43, and -18 were the most common types [7]. However, this study was performed in a hospital population. The HPV distribution in a community population remains unknown. Our study is unique as a relatively large study investigating the HPV genotype distribution among women aged 20–35 years in the community, showing that the most common HR-HPV infection types were HPV-52, -68 and -51, which carry a relatively high risk for cervical lesions and even cervical cancer.

In Fujian, as for HPV vaccine was approved for a short time, many challenges remain in the development and application of the HPV vaccine. In our study, the HPV vaccine targeted genotypes were only 13.9% (45/324) in the bivalent HPV vaccine (HPV-16/-18) and 17.9% (58/324) in the quadrivalent vaccine (HPV-6/-11/-16/-18). Although the nonavalent vaccine (HPV-6/-11/-16/-18/-31/-33/-45/-52/-58) targeted 50.00% (162/324) of the HPV genotypes, this vaccine has not been approved in Fujian. Thus, in this population, the introduction of Gardasil-9 should be encouraged. In addition, because the current HPV vaccines are both prophylactic and not effective in women with HPV infection, cervical cancer screening programs are necessary for early detection of precancerous cervical lesions and to treat HPV infection to reduce the rate of cervical cancer. Our study may provide a basis for formulating cervical cancer prevention strategies in the Fujian region.

Currently, the association between BV and cervical HPV infection identified in several studies remains controversial [17]. When analyzing the association between BV and cervical HPV infection, our study showed that HR-HPV infection was significantly correlated with BV. Our results were consistent with those of a previous study [18]. Eun et al. [19] suggested that persistent HPV infection may change the vaginal milieu in women. A study conducted by Guo et al. [18] indicated that BV may delay HPV infection clearance. Another study suggested that BV can disrupt local immune defense [20]. The reasons for the association between BV and cervical HPV remain controversial and unknown. Furthermore, it is unknown how HPV infection or BV disrupts the vaginal microenvironment balance. Vaginal microenvironment disorder has been associated with increased levels of proinflammatory cytokines and chronic inflammation at mucosal sites. Women with BV expressed increased levels of cytokine interleukin (IL)-1β and decreased levels of IL-17 [21, 22]. It has also been reported that G. vaginalis can secrete sialidase while elevated sialidase concentration was associated with increased risk for cervical lesion [23]. This type of immune activation needs to be confirmed in further studies with rigorous experimental precision.

Up until now, there are few studies focus on the correlation between BV and specific HPV genotypes. According to the results of this study, BV was found to be related to HPV-51, -52 infections. Previews study in Africa suggested that BV associate with HPV-58 [24]. Obviously, the epidemiology of HPV and genital tract infection is different in each region, and the founding of this study may guide the HPV vaccine protecting patients with recurrent BV. Our study emphasizes the importance of treating BV for preventing HPV infection, particularly for HR-HPV infections.

However, this study also has some limitations. First, BV can be diagnosed by the Amsel's criteria, Nugent scoring system, Hay-Ison score [25], and Emerging molecular and functional diagnostic methods [26]. Although Amsel's criteria is considered as the "gold standard" of BV clinically diagnosis, the method is often subject to interobserver variability as the assessment of the diagnostic criteria depends on the observer's skill and experience. So the specimens were blinded and evaluated by two experienced laboratory physicians. Secondly, our study only focused on BV, but other sexually transmitted infections such as Neisseria gonorrhoeae, Trichomonas vaginosis or Mycoplasma genitalium were not included. Nowadays, there is growing research into the relationship between other sexually transmitted infections (STI) and HPV. 11.4% of the women had at least one STI pathogen, the most common being Chlamydia trachomatis (6.7%) [27]. Chlamydia trachomatis and HPV-16, HPV-51, HPV-52 was most frequently identified in co-infections [28]. The mechanism of interaction between HPV and other pathogens is unclear. Further investigations should be conducted to explore the interaction between HPV and other pathogens, and the sample size should be expanded.