As hepatitis B had seriously endangered the lives and health of its people, the Chinese government integrated the hepatitis B vaccine into its routine immunisation management programme in 1992, and the HB vaccine was included in the national expanded immunisation programme in 2002. With these steps, the prevention and control of HBV entered a new era. With the widespread usage of HB vaccine, the epidemiological characteristics of HBV in China changed greatly. The incidences of acute and chronic HBV dropped significantly with the implementation of the hepatitis B vaccine immunisation programmes in Jiangsu province. In order to maintain HBV at a low epidemic level, we cannot slacken our efforts in the slightest with regards to the prevention and control of HBV.
The survey found that the prevalence rate of HBsAg was 0.41% in people aged 1 to 4 years, while the rate was 3.39% in the >15 years age group in 2014. Similarly, the positive rate of anti-HBc was 5.33%. The anti-HBc positive rate was higher than that in Liaoning province (4.70%),which might be attributed to the coverage, effectiveness of HB vaccine and the failure to block HBV mother to infant transmission. It is worth noting that the anti-HBc positive rate was increased with age, as other studies have observed[14, 15],, which might be attributed to the changing immunization coverage rate in the country and the increase in exposure period as well.
The survey also showed that the prevalence rates of anti-HBs in Jiangsu province for people ages 1 to 4, 5 to 15, and 15 to 29 years were 76.38% (95% CI: 73.91-78.73 %), 61.97% (95% CI: 58.79-65.08%), and 58.35% (95% CI: 54.91-61.74%), respectively. The previous studies have shown that the proportion of patients who were infected with HBV differed by age. Children infected within 1 year of birth had a 80-90% chance of developing a chronic infection. Children infected by 6 years of age had a 30-50% chance, while less than 5% of adolescents and adults developed a chronic infection. Therefore, the high level of anti-HBs in children under 6 years old plays an important role in controlling HBV. Anti-HBs levels were highest in the under-5 year group in our study due to the effect of HB vaccine, and the attenuation of antibodies over time was relatively obvious in the 15- to 29-year-old groups. This may due to the deficiencies of vaccine implement, such as vaccine damage, vaccine freezing, on time inoculation and so on, resulted in the failure of vaccination or the low-level coverage of the HB vaccine in these groups[7, 17]. Therefore, revaccination of such populations is recommended. In China, students (> 20 years old) need to complete a physical examinations before enrolling, and school health staffs could use the results of the test and recommend booster vaccination to those who do not have seroconversion. So following the routine schedule of 3-dose booster may be beneficial.
An interesting finding was that there was no significant difference in the HBsAg positive rates between urban and rural areas. Other studies in China [6, 7, 18-20], have suggested that rural areas may have a higher positive rate, mainly due to the low coverage of the hepatitis B vaccine and differences in sanitary conditions. However, in recent years, more efforts have been made to strengthen basic immunisation in rural areas. The percentage of people receiving the full three-dose immunisation series and receiving the first dose according to the recommended timeline has been greatly improved. These improvements are conducive to the reduction of perinatal transmission[21-25]. Table 1 also shows that the higher rate of receiving the first dose according to the recommended time frame is closely related to lower positive rates of HBsAg and Anti-HBc. Previous studies have found that the infection rate of HBV in males is higher than that in female [20, 26-28], however, this study found no significant correlation between the positive rate of HBsAg and gender (male: 1.33% vs female: 1.06%, P > 0.05). This finding suggests that our long-term HBV vaccine strategy has changed the gender distribution of HBV. Our data also suggest that the positive rates of HBsAg and Anti-HBc are strongly related to educational level. Adults who had completed higher education were far less likely to be positive than those with a lower education level. This finding agrees with the results of many previous studies [7, 29, 30]. It is possible that people with higher education levels more efficiently utilise health services, such as health education, hospital resources and others.
The prevalence rates of HBsAg, Anti-HBc and Anti-HBs were significantly different between the participants with and without an HBV immunisation history, which reflects the critical role of HB vaccine in controlling HBV. As more research is published, most results have suggested that the protective effect of a routine full-course immunisation series can last 10-18 years [31-34]. The present study found that the level of anti-HBs increased significantly in 2014 compared with 2006(see, figure 3). There may be three reasons for this result. First, HB vaccine was introduced into China in 1992; Second, HB vaccine was integrated into the EPI; Third, catch-up strategies targeting all previously unvaccinated children aged <15 years was adopted as a supplement to routine infant vaccination [6, 7]. Other studies have suggested that a HB vaccine booster immunisation should be given 18 years after the completion of the first vaccination series or earlier . However, due to different types and immunisation procedures for HB vaccine, as well as differences in the effectiveness and immunogenicity of HB vaccine in different ethnic groups, the above result should be studied in China to determine whether it is appropriate in the Chinese population. Additionally, we found that 12 HBsAg-positive participants failed to respond to HB vaccine. 5 participants were in the age group of 1 to 4 years, and 7 people in the 5 to 29 age group. In addition, there were 3 participants in the 15-29 age group whose value of anti-HBs is lower than 10 mIU/ml, and the other family members of five positive participants were also HBsAg-positive. There are many factors influencing the effectiveness of the vaccination. Some studies found that antibody levels showed a significant decline in children after HB vaccination in infancy [36-38]. One potential reason may be vaccination age [39, 40]. Other factors that may influence the effectiveness of the vaccine include smoking, obesity, HIV infection, genetic factors and other chronic diseases [41-45].
This study had three key limitations. First, Although this seroepidemiological survey used a cross-sectional design , they were strictly involved random sampling according to the rules. Second, the participants were people who had lived in the surveillance points for six months. Many migrants or unregistered children outside of family planning were excluded, especially in some urban areas, HBsAg prevalence rates in these groups may be higher than those reported in this study, so we may have underestimated the overall prevalence in the province. Third, because the adults included in this study did not have their vaccination records, the acquisition of adult immunisation history was done by individual recall.