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Encephalitis temporally associated with live attenuated Japanese encephalitis vaccine: four case reports

Na Jia1, Qiu-Min Zhao1, Xiao-Fang Guo2, Jing-Xia Cheng3, Chao Wu2, Shu-Qing Zuo1, Pei-Fang Dai3, Jun-Ying Zhao3 and Jiu-Song Zhang1*

Author Affiliations

1 State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, 20 Dong Da-Street, Fengtai District, Beijing 100071, People's Republic of China

2 Yunnan Institute of Parasitic Diseases, Pu'er 665000, People's Republic of China

3 Shanxi Center for Disease Control and Prevention, Taiyuan 030012, People's Republic of China

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BMC Infectious Diseases 2011, 11:344  doi:10.1186/1471-2334-11-344

Published: 14 December 2011



Japanese encephalitis (JE) vaccination is the most effective measure for preventing JE disease. The live attenuated JE vaccine, which has shown good efficacy and safety, has been widely used in China.

Case presentations

We report four laboratory-confirmed JE cases detected in JE-endemic areas during the JE virus (JEV) transmission season, who all received a first dose of live attenuated JE vaccine within 2 weeks prior to the onset of illness. All cases presented with acute encephalitis and rapidly reduced consciousness. All cerebrospinal fluid (CSF) samples from the patients were positive for JEV-specific immunoglobulin M (IgM) antibodies, but viral isolation and polymerase chain reaction (PCR) detection of JEV were both negative.


It is difficult to identify a causal link between the disease and the vaccination, as the source of positive CSF JEV IgM antibodies might be natural JEV infection or possibly due to a traumatic lumbar puncture. Our observations highlight the need for public health officers and doctors to consider reasonable vaccination policies during the JE season. In addition, continued surveillance as well as thorough investigation of any events that occur after JE vaccination is necessary.