Retention of neutralizing antibodies to Japanese encephalitis vaccine in age groups above fifteen years in Korea

Abstract

Background: The incidence of Japanese encephalitis (JE) markedly decreased after the national immunization program in Korea, but is still intermittently reported in adults. Prospective studies are needed to determine whether JE virus (JEV)-neutralizing antibody (NAb) levels decline with age after the final JE vaccination. This study evaluated the titers of NAbs against JEV in Korean adolescents and adults. Methods: Specimens were collected from normal, healthy individuals aged 1 to ≥70 years (a total of 1605 cases) from five regional hospitals in Korea. Neutralizing antibody (NAb) titers were determined using a pseudotyped JEV NAb assay. Results: The JEV NAb-positive population was >95% in the 15–29 years age group, 89.42% in the 30–44 years age group, 75.24% in the 55–59 years age group, and 59.77% in the ≥70 years age group. NAb titers from the 20 to 70 years age groups showed a progressive decrease in proportion to age (p < 0.0001). Conclusions: Retention of NAbs after the final JE vaccination in childhood is a key indicator of the vaccination program and will have a significant impact on future JE prevention strategies.

Keywords

• Japanese encephalitis
• Neutralizing antibody
• Vaccination
• Retention
• Korea