The target population was local residents of all age groups living in Jiangsu provinces, Eastern China (Supplemental Figure 1). Participants were selected as representative of the population of Eastern China, in that there was no statistically significant difference between participants in this study and the whole of Eastern China in demographics, the situation of the population or economic conditions. All local residents who had resided in Jiangsu for > 6 mo at the time of the survey were selected. A list of residents was obtained from the Residents’ Committee.

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Figure 1 Age, gender-specific prevalence of hepatitis B surface antigen in China.

The sample size was calculated as following:

n = p(1 - p)/(d/z_a)² = z_a²×p(1 - p)/d²

where p means the estimated prevalence rate, d represented power and was calculated by 0.1 ×p and z_α was the statistics of α. For this study, α was set 0.05. Considering the variance of hepatitis C virus prevalence in different age groups in the survey (0.5% for age < 5 years, 1.5% for age 5-19 years, and 8% for age > 19 years), the desired sample size was 110466, and included 79600 people age < 5 years, 26266 people age 5-19 years, and 4600 people age > 19 years.

To represent the population of the whole province, a multistage sampling method was applied. First, the whole province was divided into three major groups (south, middle and north) determined by regional distinctions in earnings, education level, awareness of health care among the inhabitants, and health care system. One county was randomly selected from each major regional group: Zhangjiagang, Danyang and Taixing were chosen to represent south, middle and north sites, respectively. There were 887 communities in these three counties, and 20 communities were randomly chosen in each county. Finally, all local residents from those 60 communities were targeted for participation in this study by cluster sampling.

Before the survey was administered, community doctors issued a notice of physical examination to each household in the list of residents. The letter introduced the survey objective, examination items, and matters needing attention. Local residents willing to participate arrived at the survey spots in the community hospital at the appointed time. In each community hospital, there was a survey location and a team of 20-25 trained staff, including physicians, nurses, and community doctors, to carry out the investigation. A structured questionnaire was used by trained staff to ask basic information such as name, gender, birth date, education, occupation, marital status, smoking, drinking, history of hypertension and diabetes, immunization and familial history of HBV, and possible risk factors. All investigations were conducted through face to face interviews. Information on children under 15 years old was provided by their parents. Educational level was defined by academic certificate. Persons who had frequent contact with the public, such as an employee in a hotel, restaurant, barbershop, and market, were defined as public service workers. Children under 17 years old established their immunization status from the record of the immunization certificate kept by the parents. If they had no information about hepatitis B immunization, it was necessary to review the village doctor’s registry; if these sources were not available, the status was recorded as unvaccinated. In cases in which adults had no immunization records, immunization information for adults was from memory recall (vaccinated, unvaccinated, or unknown).

Blood samples collected from each study participant included 5 mL for the population aged > 2 years and 2 mL for children aged ≤ 2 years. Blood samples were collected without anticoagulant and were separated by centrifugation at 1800 ×g for 10 min and room temperature. Serum samples were stored at -70 °C. These procedures were completed within 6 h of sample collection. All samples were collected and frozen according to standardized procedures and tested in a central laboratory. HBsAg was detected by EILSA (Kehua Bio-Engineering Co. Ltd., Shanghai, China). Each reaction plate included two negative controls, three positive controls, and one blank control. More than 10% of the samples were randomly selected for repeated assays, and the results were 97% concordant.

Differences in demographic characteristics between HBsAg-positive and -negative groups were calculated using the Student t test or one-way analysis of variance (for continuous variables) and the χ² test (for categorical variables). The associations of potential risk factors with HBV infection risk were estimated by computing the ORs and their 95%CIs from both univariate and multivariate logistic regression analyses. The Cochran-Armitage test was used for trend analysis. All statistical analyses were performed with SAS 9.1.3 software (SAS Institute, Cary, NC, United States), and P < 0.05 in a two-sided test was considered statistically significant.

The characteristics of the study population are shown in Table 1. Among the 148931 participants, 0.79% were aged 1-4 years, 18.83% aged 5-19 years, and 80.38% ≥ 20 years. The male to female ratio was 0.82:1. Among those aged ≥ 20 years, 88.88% were married, 57.27% were illiterate or had a primary school diploma, 33.72% were agricultural workers, and 72.80% and 79.75% never smoked and drank, respectively. The proportion of those adults without a history of hypertension and diabetes were 82.97% and 97.49%, respectively. In all age groups, subjects with a familial history of HBV and those reporting any hepatitis B vaccination were 8.23% and 34.28%.

Among the 148931 participants studied, 11469 were HBsAg positive, while the overall prevalence of HBsAg in this study population was 7.70% (95%CI: 7.57%-7.84%). There was a great variation in HBsAg positivity among different age and gender groups. The prevalence was low in children (0.70%-0.77%), but increased progressively from adolescents (1.40%-2.55%) to adults aged ≥ 20 years (5.69%-11.22%) (Figure 1). Meanwhile, men had a higher prevalence of HBV infection than women in all age strata except the 5-9 years age group.

The prevalence of HBsAg stratified by other demographic and selected variables in this study population is described in Table 2. Significant differences were observed in marital status, education level, occupation, immunization and familial history of HBV about the prevalence of HBsAg. Among participants aged ≥ 20 years, the HBsAg prevalence among married participants (9.41%, 95%CI: 9.24%-9.59%) was higher than among the unmarried (7.36%, 95%CI: 6.75%-8.02%) or divorced (7.28%, 95%CI: 6.65%-7.95%) participants. HBsAg prevalence increased with decreasing education level. Participants who were illiterate or had primary school diplomas had the highest HBsAg prevalence (9.82%, 95%CI: 9.60%-10.05%), followed by middle school (8.35%, 95%CI: 8.09%-8.62%) and college school groups (8.05%, 95%CI: 7.42%-8.70%). HBsAg prevalence was significantly lower among students (6.81%, 95%CI: 5.48%-8.35%) and unemployed groups (6.74%, 95%CI: 6.41%-7.08%). The prevalence of HBsAg was higher in participants who had no history of hepatitis B vaccine, while it was lower in participants without a family history of HBV (P < 0.05 for both comparisons).

The frequency of various risk factors associated with HBV infection and the calculated crude OR estimated by univariate and multivariate analysis are shown in Tables 3 and 4. Among the population aged 1-19 years, age, sex, hepatitis B immunization, and familial history of HBV were correlated with HBsAg positivity. However, after adjusting for those variables, older age (OR = 4.12, 95%CI: 1.93-8.75 for 15-19 years vs 1-4 years group) and familial history of HBV (OR = 2.0, 95%CI: 1.88-2.13) were associated with an increased risk of HBV infection. Participants with a history of immunization had a 29% decrease in the risk of HBV infection.

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Figure 3 Age- and hepatitis B immunization-specific prevalence of hepatitis B surface antigen in China.

Among the population aged ≥ 20 years, univariate logistic regression showed that age, sex, hepatitis B immunization, familial history of HBV, invasive testing, and sharing needles were correlated with HBsAg positivity. After adjusting for those variables, older age (OR = 1.18, 95%CI: 1.08-1.30 for 30-39 years vs 20-29 years group), familial history of HBV (OR = 1.93, 95%CI: 1.83-2.05), invasive testing (OR = 1.18, 95%CI: 1.11-1.26), and sharing needles (OR = 1.44, 95%CI: 1.12-1.86) were associated with an increased risk of HBV infection. However, female gender and a history of HBV immunization had a significant decrease in the risk of HBV infection (OR = 0.72, 0.52 for gender and immunization, respectively).

Among the 148931 participants studied, 12016 (8.28%, 95%CI: 8.14%-8.43%) had a familial history of HBV. When different classes of relatives were analyzed separately, HBV infection risks showed a statistically significant increase for mothers, fathers, spouses, offspring and siblings (Table 5). In particular, mothers and siblings who were HBsAg seropositive significantly increased risk by 25.7% and 21.0%, respectively. We evaluated the combined effects by adding up the number of families with HBsAg seropositivity. The ORs for risk of HBV infection increased concomitantly with the number of HBsAg-seropositive family members (Table 5). Participants with 3-6 family members who were HBsAg seropositive were significantly associated with HBV infection (OR = 9.82, 95%CI: 4.80-20.11), compared with participants without a familial history of HBV.

Among the 126101 participants effectively surveyed about hepatitis B immunization, 50233 (39.84%, 95%CI: 35.57%-40.11%) had a history of HBV immunization. There was a significant decreasing trend in vaccination prevalence associated with increasing age (Figure 2). There was great variation in immunization prevalence among different age groups, ranging from 98.75% to 4.59%. The rate among children aged 1-19 years born after the hepatitis B vaccine was recommended for routine childhood immunization was 93.30% (95%CI: 93.01%-93.58%). Among all hepatitis-B-vaccinated persons in this study, the main methods of immunization were planned immunization and collective organization vaccination (44.84% and 41.10%, respectively). The main reason for lack of immunization was that participants had little information about hepatitis B vaccination (80.60%).

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Figure 2 Age-specific prevalence of hepatitis B immunization in China.

The prevalence of HBsAg among vaccinated persons was only 3.59% (95%CI: 3.56%-3.90%), compared to 10.22% (95%CI: 10.15%-11.63%) among unvaccinated persons (P < 0.001). This difference was proportionally greater in adult groups (Figure 3).

Hepatitis B virus (HBV) poses a serious global health problem because of its adverse clinical outcomes, such as cirrhosis and hepatocellular carcinoma. The WHO estimates there are approximately 2 billion people infected by HBV worldwide, and 240 million of them have chronic infection. In China, a highly endemic area, the national prevalence for hepatitis B surface antigen (HBsAg) positivity is 7.20%.

Many studies have suggested that the incidence of newly acquired HBV infection in China has declined steadily since the 1990s by virtue of a number of public health interventions, such as the screening of pregnant women and the vaccination of infants and adolescents, the promotion of safe injection practices, and the development of health education in general. Yet HBV infection prevalence is still high among Chinese high-risk populations such as drug users and men who have sex with men.

The present study aimed to evaluate the impact of the hepatitis B vaccination program since 1992 in a large general population, and to clarify the relationship between socioeconomic status or familial history and the HBV carrier state.

7.70% were positive for HBsAg which has not achieved the national goal for the whole population in decreasing the prevalence of HBsAg to < 7%. The prevalence was just 0.77% among children aged < 5 years and the rate of HBV immunization among teenagers < 20 years was 93.30%, which have reached the national goal of < 1% and > 90%, respectively.

It is important to know impact of the hepatitis B vaccination program. The study is innovative in nature. The original study conducted on large groups of participants is very valuable.