A recombinant hepatitis E vaccine, Hecolin®, has been proven safe and effective in healthy adults. As hepatitis B surface antigen (HBsAg) positive individuals have a higher risk of poor prognosis after super-infection with hepatitis E virus (HEV), the safety and immunogenicity of Hecolin® in this population should be assessed. The present study is an extending analysis of data from a large randomized controlled clinical trial of Hecolin®. Healthy participants (n = 14,065) without current or previous evidence of chronic liver disease were randomized to receive Hecolin® or placebo (hepatitis B vaccine) and donated their blood samples before vaccination and subsequently over 31 mo. Most of the adverse events were mild and comparable between participants with and without baseline hepatitis B surface antigen (HBsAg). No vaccine-related serious adverse events were reported. Rates of serious adverse events in HBsAg (+) or HBsAg (-) participants were also comparable between both groups. Almost all participants in the Hecolin® group seroconverted to anti-HEV one month after full vaccination. The antibody response rates and levels were similar in HBsAg (+) and HBsAg (-) participants (98.38%, 19.32 Wu/mL vs. 98.69%, 19.00 Wu/mL). The two-year antibody dynamics of HBsAg (+) participants overlapped perfectly with those of HBsAg (-) participants. In conclusion, the safety and immunogenicity of Hecolin® for HBsAg (+) adults is very similar to that for the general population.

A pseudovirion-based neutralisation assay (PBNA) has been considered the gold standard for measuring specific antibody responses against human papillomavirus (HPV). However, this assay is labor intensive and therefore very difficult to implement in large-scale studies. Previous studies have evaluated the agreement between virus-like particle (VLP)-based ELISA and PBNA for measuring HPV vaccine-induced antibodies. However, the concordance of these assays to detect antibodies induced by natural infection has not yet been fully elucidated. In this study, the results of an Escherichia coli (E. coli)-expressed VLP-based ELISA were found to be highly concordant with those of a baculovirus-expressed VLP-based ELISA (r = 0.96 and 0.97 for HPV-16 and HPV-18) when detecing HPV vaccine induced antibodies and the concordance was medium (r = 0.68 and 0.68 for HPV-16 and HPV-18) when assessing natural infection induced antibodies. The results of the E. coli expressed VLP-based ELISA correlated well with those of the PBNA when testing 1020 post-vaccination human sera collected at one month after vaccination with the E. coli expressed VLP-based bivalent HPV vaccine (r = 0.83 and 0.81 for HPV-16 and HPV-18). The agreement and correlation were moderate (kappa < 0.3 for both HPV types 16 and 18, r = 0.59 and 0.68 for HPV-16 and HPV-18, respectively) when assessing 1600 serum samples from unvaccinated women of age 18–25 years. In conclusion, the VLP-based ELISA is an acceptable surrogate for the neutralizing antibody assay in measuring vaccine responses. However, the use of the VLP-based ELISA in epidemiological studies should be carefully considered.

Special attention has been paid to Hepatitis E (HE) prophylaxis for pregnant women due to poor prognosis of HE in this population. We conducted a post-hoc analysis based on the randomized, double-blind, HE vaccine (Hecolin)-controlled phase 3 clinical trial of human papillomavirus (HPV) vaccine (Cecolin) conducted in China. Eligible healthy women aged 18–45 years were randomly assigned to receive three doses of Cecolin or Hecolin and were followed up for 66 months. All the pregnancy-related events throughout the study period were closely followed up. The incidences of adverse events, pregnancy complications, and adverse pregnancy outcomes were analysed based on the vaccine group, maternal age, and interval between vaccination and pregnancy onset. During the study period, 1263 Hecolin receivers and 1260 Cecolin receivers reported 1684 and 1660 pregnancies, respectively. The participants in the two vaccine groups showed similar maternal and neonatal safety profiles, regardless of maternal age. Among the 140 women who were inadvertently vaccinated during pregnancy, the incidences of adverse reactions had no statistical difference between the two groups (31.8% vs 35.1%, p = 0.6782). The proximal exposure to HE vaccination was not associated with a significantly higher risk of abnormal foetal loss (OR 0.80, 95% CI 0.38–1.70) or neonatal abnormality (OR 2.46, 95% CI 0.74–8.18) than that to HPV vaccination, as did distal exposure. Significant difference was not noted between pregnancies with proximal and distal exposure to HE vaccination. Conclusively, HE vaccination during or shortly before pregnancy is not associated with increased risks for both the pregnant women and pregnancy outcomes.