Seroprevalence of Japanese Encephalitis Virus, and Immunogenicity of the Vero-Cell Culture-Derived Vaccine in Hematopoietic Stem Cell Transplantation Recipients

Abstract

Background: Revaccination against Japanese encephalitis virus (JEV) in adult hematopoietic stem cell transplantation (HSCT) recipients is not recommended because of insufficient data regarding its efficacy and immunogenicity. Therefore, we aimed to evaluate JEV seropositivity in adult HSCT recipients and explored the seroconversion rate in pediatric HSCT recipients after vaccination against JEV. Methods: This prospective study was conducted at the National Cancer Center, Goyang, Korea. Adult HSCT recipients (n = 103) were enrolled who visited the outpatient clinic. Additionally, pediatric recipients (< 19 years old; n = 11) who received JEV vaccination were enrolled. We collected serum samples from these participants and healthy healthcare workers (n = 50) for comparison. The JEV seropositivity rates and anti-JEV antibody titers were evaluated using the plaque reduction neutralization test. Results: The JEV seropositivity rates were significantly lower in adult HSCT recipients than in healthy healthcare workers (55% vs. 92%, P < 0.001). In addition, only one out of nine pediatric recipients tested seropositive before JEV vaccination. However, six out of seven were seropositive after two doses of vaccination. Furthermore, all three recipients who completed the three-dose vaccination schedule turned seropositive. No significant seropositivity-related factors were identified in the multivariate analysis. Conclusion: The low anti-JEV antibody seropositivity rate in Korean adult HSCT recipients indicates an increased vulnerability to this virus. Our findings provide a theoretical basis for the potential establishment of appropriate prevention strategies targeting this high-risk group.