Haartman Institute, Faculty of Medicine, University of Helsinki, Finland.
Clin Infect Dis. 2012 Sep;55(6):825-34. doi: 10.1093/cid/cis542. Epub 2012 Jun 13.
A significant part of the world population lives in areas with endemic Japanese encephalitis (JE). For travelers from nonendemic countries, Vero cell-derived vaccine (JE-VC; Ixiaro) has replaced traditional mouse brain-derived vaccines (JE-MB) associated with safety concerns. The 2 vaccines are derived from different viral strains: JE-VC from the SA14-14-2 strain and JE-MB from the Nakayama strain. No data exist regarding whether JE-VC can be used to boost immunity after a primary series of JE-MB; therefore, a primary series of JE-VC has been recommended to all travelers regardless of previous vaccination history.
One hundred twenty travelers were divided into 4 groups: Volunteers with no prior JE vaccination received primary immunization with (group 1) JE-MB or (group 2) JE-VC, and those primed with JE-MB received a single booster dose of (group 3) JE-MB or (group 4) JE-VC. Immune responses were tested before and 4-8 weeks after vaccination using plaque reduction neutralization test (PRNT) against both vaccine strains.
In vaccine-naive travelers, the vaccination response rate for test strains Nakayama and SA14-14-2 was 100% and 87% after primary vaccination with JE-MB and 87% and 94% after JE-VC, respectively. Antibody levels depended on the target virus, with higher titers against homologous than heterologous PRNT(50) target strain (P < .001). In travelers primed with JE-MB, vaccination response rates were 91% and 91%, and 98% and 95% after a booster dose of JE-MB or JE-VC, respectively. Subgroup analysis revealed that a higher proportion of primed (98%/95%) than nonprimed (39%/42%) volunteers responded to a single dose of JE-VC (P < .001).
A single dose of JE-VC effectively boosted immunity in JE-MB-primed travelers. Current recommendations should be reevaluated.
NCT01386827.
世界上很大一部分人口生活在日本脑炎（JE）地方性流行地区。对于来自非地方性流行国家的旅行者，Vero 细胞衍生疫苗（JE-VC；Ixiaro）已取代与安全性相关的传统鼠脑衍生疫苗（JE-MB）。这 2 种疫苗源自不同的病毒株：JE-VC 源自 SA14-14-2 株，JE-MB 源自 Nakayama 株。关于 JE-VC 是否可用于增强 JE-MB 系列疫苗的初次免疫后的免疫力，尚无相关数据；因此，建议所有旅行者（无论之前是否接种过疫苗）都接种 JE-VC 系列疫苗的初次免疫。
120 名旅行者分为 4 组：未接种过 JE 疫苗的志愿者接种（第 1 组）JE-MB 或（第 2 组）JE-VC 作为初次免疫，接种过 JE-MB 的志愿者接种（第 3 组）JE-MB 或（第 4 组）JE-VC 作为加强免疫。使用蚀斑减少中和试验（PRNT）检测接种前后针对疫苗株 Nakayama 和 SA14-14-2 的免疫应答。
在疫苗初免旅行者中，接种 JE-MB 后，Nakayama 和 SA14-14-2 测试株的疫苗接种反应率分别为 100%和 87%，接种 JE-VC 后分别为 87%和 94%。抗体水平取决于靶病毒，针对同源 PRNT（50）靶株的滴度高于异源 PRNT（50）靶株（P <.001）。在接种过 JE-MB 的旅行者中，接种 JE-MB 或 JE-VC 加强免疫后，疫苗接种反应率分别为 91%和 91%，98%和 95%。亚组分析显示，与非初免者（39%/42%）相比，初免者（98%/95%）对 JE-VC 的单剂反应比例更高（P <.001）。
JE-VC 单剂可有效增强 JE-MB 初免旅行者的免疫力。目前的建议应重新评估。
NCT01386827。
