Prevalence of chronic hepatitis B and status of HBV care among rural women who planned to conceive in China

Globally, one third of prevalent chronic hepatitis B (CHB) virus infection (HBV) occurred in China. Assessing the prevalence of CHB infesction and status of HBV-related services among pre-conception women will provide insight into risks of mother to child transmission (MTCT). A cross-sectional analysis of data from the National Free Pre-pregnancy Checkups (NFPC) program in 2010–2014 was conducted. A standardized questionnaire which collected demographic information and enzyme-linked immunosorbent assays (ELISA) which tested serological HBV markers were applied. A total of 16,051,850 rural women aged 15–49 years were included. 5.2% of women were infected with CHB, among whom, 28.6% were also hepatitis B e antigen (HBeAg) positive. The most CHB concentrated places were distributed in southeastern coastal provinces. Women born after 1992 did not experience a higher level of vaccine-induced immunity compared to those born before 1992. Nine in ten rural women with CHB were not aware of their HBV status and a very small proportion of women (0.22%) had received antiviral treatment. Our data demonstrated an overall high-intermediate burden of CHB. Heterogeneity of geographic distribution, high proportion of HBeAg, insufficient awareness of HBV status, and low access to HBV treatment are challenges for preventing the MTCT.

Rural women in China often had poor education and limited resources 6 and were likely to resemble populations from other low and middle income countries in terms of education and available resources. Knowing their status of CHB and status of hepatitis B-related services will have important implications onglobal control of CHB. Worldwide, most of CHB has been acquired perinatally or in early childhood 7 , and up to 50% of new HBV infections were obtained through mother-to-child-transmission (MTCT) in China 8 . Identifying women with CHB prior to their pregnancy and gaps of policy implementation are crucial for the prevention of MTCT.
In this study, we reported the prevalence of CHB, geographic distribution and status of hepatitis B-related services among 16 million rural women aged 15-49 years in China, evaluated the effect of the national HBV immunization program on serological outcome in women born before and after 1992 and main focused on challenges on mother to child transmission of HBV.

Methods
Study design and study population. A cross-sectional study was conducted, using data from the National Free Pre-pregnancy Checkups (NFPC) program. Women aged 15-49 years who planned to conceive and attended NFPC between January 2010 and December 2014 were included. It is noted that a previous report using 2014 data has demonstrated the burden of HBV in this population. Here we used expanded samples from 2010-2014 to see if the conclusions remain and to explore other prioritized questions 9 . The NFPC, supported by the Chinese National Health and Family Planning Commission and Ministry of Finance, is a nationwide free preconception medical examination service for rural couples in China. It was first carried out in 100 counties of 18 provinces in 2010 in China, and was gradually extended to 2790 counties in 2013 with high coverage across the country. Since the NFPC is a free program aiming to improve the health of pregnancy and reduce birth defects, and women voluntarily came to obtain the service, the selection of study population would belong to the convenience sampling.
All couples who planned to conceive were enrolled by trained staff, and informed consent was obtained before the checkups. A face-to-face interview was then carried out by qualified nurses using a standardized procedure. Socioeconomic information including age, occupation, education, ethnicity, and residence was collected by a structured questionnaire. A 5 mL-blood sample was obtained and tested for HBV serologic markers at local laboratories. Tests included hepatitis B surface antigen (HBsAg), hepatitis B surface antibody (anti-HBs), hepatitis B e antigen (HBeAg), hepatitis B e antibody (anti-HBe) and hepatitis B core antibody (anti-HBc) using ELISA kits approved by the China Food and Drug Administration. Quality control was completed by the National Center of Clinical Laboratories with reagents produced by Abbott (Abbott Park, IL, USA), as the reference standard. Study protocols and forms were approved by the Institutional Research Review Board at the National Research Institute for Family Planning. The study was carried out under the guidance of the protocols strictly.    10 , a self-reported history of HBV immunization (yes, no) and parity (0, ≥ 1). To explore the impact of the national HBV immunization program beginning in 1992, study population were divided into a cohort born before 1992 and a cohort born after 1992.
Statistical analysis. We present the distribution of participants' socio-demographic characteristics using proportions. The prevalence of each outcome and 95% confidence interval (CI) were calculated in the entire population, as well as in subgroups. We employed Poisson regression models to assess the crude and adjusted prevalence ratio (PR) of outcomes. Adjusted variables for awareness of HBV status were age, education, ethnic group, occupation, migrant population, region and parity. The effect of the national HBV immunization program was analyzed by comparing the difference of each serological outcome in women born before and after 1992. In addition, to describe the geographical distribution, we estimated the prevalence of CHB in each of 2,421 counties after exclusion of counties with no data or sample size less than 100 (assume unstable), and then county-specific       (Fig. 2). Women who were born after 1992 had a lower prevalence of CHB (4.7% vs 5.3%), past/present HBV infection (8.3% vs 10.5%), and vaccine-induced immunity (26.2% vs 29.3%) compared to those born before1992 Table 3).

Results
Of 837,372 women with CHB, only 85,725 (10.2%) were aware of their HBV status. Age 15-24 years and 30-49 years (vs 25-29 years), education of senior school or less (vs college or higher), living in eastern or central region (vs western region) and zero parity (vs ≥ 1) were significantly associated with a lower prevalence of awareness of HBV status (Table 4). 1874 (0.22%) women had received some therapies related to hepatitis B. Using alanine transaminase (ALT) > 2 upper limits of normal (2 ULN = 76 U/L) and HBeAg positivity as criteria for the initiation of treatment for CHB 10

Discussion
This study reports a high-intermediate burden of chronic HBV infection in a large sample of women aged 15-49 years from rural China who planned to conceive. Superimposed on this, the heterogeneity of geographic distribution and low vaccine induced immunity even among women born after 1992 when China began to recommend HBV vaccination, are barriers to prevention of MTCT of HBV infection. Most women (90%) with CHB were not aware of their status, and only a very small proportion of them had a history of antiviral therapy despite a  substantial proportion (7.4%) who may qualify, which acts as additional barriers to prevent MTCT. Although CHB can be controlled with timely and careful monitoring and appropriate treatment, these data show that preventive education and access to the clinical care among rural women with CHB are not far from optimum. The overall prevalence of CHB (5.2%) was lower than 8.7% in 2006 4 and 9.7% in 1992 12 in the same age groups, reported in two latest national HBV seros urveys. Also, the prevalence of CHB among rural men from the same data source was higher than rural women (7.0% vs 5.2%) 13 .
Geographically, 16% of provinces and 18% of counties in China still had high endemicity of HBV infection ( >8%) among rural women aged 15-49 years. The most HBV concentrated places are southeastern coastal provinces, including Guangxi, Guangdong, Fujian, Hainan, and Jiangxi. It is hard to distinguish whether individual factors, like low socio-economic status and inter-province migration 14 , or factors related to geographical locations, like historical HBV endemicity and higher risk of sexual transmission in these places, contribute to this aggregation. Besides figuring out contributing factors, preventive efforts, like screening and education, targeting on these clustered locations are recommended.
The Chinese government recommended HBV immunization for newborns in 1992. Because of high prices and unequal access to vaccines in early years 15 , people born before or close to 1992, would not benefit from this policy. Our results showed that even for women born after 1992, either overall immunity or vaccine-induced immunity against HBV did not improve compared to that of women born before 1992. Of note, women who reported a history of HBV immunization had a lower prevalence of CHB (4.4% vs 5.5%) and higher proportion of overall immunity (41.4% vs 31.3%) versus those without a self-reported history of HBV immunization. This reminds that although women missed their immunization at birth or early childhood, being vaccinated later in adulthood may still be protective.
The high proportion of positivity of HBeAg, an indication of high infectivity 16 , among women with chronic HBV infection could facilitate the risk of MTCT. Although administration of hepatitis B vaccination in conjunction with HBIG among newborns is highly effective to prevent transmission 7 ,about 7% of infants born to mothers with high viral load, indicated by positivity of HBeAg, could still be infected with HBV 17 . Our data showed that 29% of rural women with CHB were also HBeAg positive. It means not only is the burden of CHB high, but women infected with CHB are at higher risk of transmitting the disease to others, like their future babies.
As outlined by WHO in 2015, in the management of chronic HBV infection 7 , being tested and diagnosed is the first step to link people to care. Those subjects with active hepatic inflammation should be linked to care and evaluated for antiviral therapy. Our results showed that nine in ten rural women with chronic HBV infection were not aware of their status and a very small proportion of women had received treatment (0.22%) despite more women in need of antiviral therapy (7.4%). A recent study showed that Tenofovir regimen in pregnant women during their pregnancy in conjunction with a standard newborn immunoprophylaxis could significantly decrease the rate of MTCT compared to group who only had a newborn immunoprophylaxis 17 . This suggests that decreasing viral load to a suppressed level among pregnant or prenatal women through antiviral treatment is key to add further protection from MTCT. However, rural women with CHB in this study had a very low rate of receiving antiviral treatment, which makes it impossible to suppress their viral load to a safe level and prevent MTCT effectively.
The data includes a very large sample of rural women who planned to conceive, who represent a critical reservoir for the continued MTCT of HBV in China. Also, this is the first study to evaluate the status of HBV care among rural women in China, which can inform better prevention and treatment service delivery. Limitations include inability of generalizing results to the entire population since the study population comprised only rural women from a convenience sample; a potential selection bias as women who participated in the study may differ from those who had not participated; lack of quantification of viral load and anti-HBs titer; lack of continuous monitoring to confirm eligibility of antiviral treatment; a recall bias of self-reported awareness of HBV status and antiviral treatment experience.
In conclusion, our data demonstrate a high-intermediate burden of chronic HBV infection in China. The heterogeneity of geographic distribution, high proportion of HBeAg, insufficient awareness of HBV status, and low rate of antiviral treatment are deteriorating health among rural women with CHB and they will also be reservoirs for the continued MTCT of HBV in China. Public health efforts to improve awareness of HBV, to provide a catch-up vaccination and to increase uptake of appropriate antiviral treatment should be scaled up immediately.