Correspondence

Effectiveness of One Dose of SA 14-14-2 Vaccine against Japanese Encephalitis

N Engl J Med 2009; 360:1465-1466April 2, 2009

Article

To the Editor:

Japanese encephalitis remains a major cause of viral encephalitis in Asia, imposing a significant burden on poor rural families. Vaccination is an important element of disease control. Japanese encephalitis is endemic in the eastern districts of Uttar Pradesh, and these districts had a severe epidemic of the illness in 2005,1 after which a decision was made to import the Chinese live attenuated vaccine (SA 14-14-2 strain). Since 2006, summer campaigns for mass vaccination against Japanese encephalitis have been conducted among children 1 to 15 years of age in selected districts of the state. The 2007 cycle covered several districts in the catchment area of our hospital.

We studied the efficacy of a single dose of this vaccine within 6 months after its administration in India, using a case–control design similar to that described in previously published studies.2,3 Our study was approved by the university's institutional review board. Informed consent was received from the parents of the patients.

Children admitted to our hospital with an illness that was consistent with encephalitis were tested for Japanese encephalitis IgM antibodies in serum or cerebrospinal fluid by means of commercial IgM antibody–capture enzyme-linked immunosorbent assay kits (Excyton).4 In villages where the campaign for vaccination against Japanese encephalitis had been held in the summer of 2007, children with laboratory tests that were positive for Japanese encephalitis virus were evaluated. A history of vaccination was elicited, and investigators asked for a vaccination card. After the Japanese encephalitis season, trained investigators visited the villages of patients. Parents of available age- and sex-matched controls living in the same neighborhood were interviewed regarding a history of vaccination.

Twenty patients with Japanese encephalitis were identified, of whom 4 had been vaccinated. Cerebrospinal fluid from 15 of the 20 patients, including all 4 vaccinated patients, was positive for IgM antibodies against Japanese encephalitis. A vaccination card was available for all four vaccinated patients. Of a total of 441 controls, the vaccination status could be confirmed in 429. Of these controls, 339 (79.0%) had been vaccinated, and 90 had not been vaccinated. The campaign-style vaccination program was easily recalled. The crude odds ratio for disease among vaccinated children was 0.07 (95% confidence interval [CI], 0.02 to 0.22), the exact odds ratio was 0.055 (95% CI, 0.012 to 0.184), and the vaccine efficacy was 94.5% (95% CI, 81.5 to 98.9) (Table 1Table 1Efficacy of the SA 14-14-2 Vaccine against Japanese Encephalitis.). The efficacy of a single dose of the SA14-14-2 vaccine for the prevention of Japanese encephalitis for 6 months after vaccination in Uttar Pradesh is consistent with the efficacy reported in previous studies in Nepal.2,3

Rashmi Kumar, M.D.
Piyush Tripathi, M.Sc.
Chhatrapati Shahuji Maharaj Medical University, Lucknow 226003, India
rashmik2005@gmail.com

Anwar Rizvi, B.M.S.
Maseeha Cancer Foundation, Lucknow 226003, India

Supported by a grant (5/8/7/13/2001-ECDI, to Dr. Kumar) from the Indian Council of Medical Research, New Delhi.

4 References

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   Ohrr H, Tandon JB, Sohn YMN, Shin SH, Pradhan DP, Halstead SB. Effect of single dose of SA 14-14-2 vaccine 1 year after immunisation in Nepalese children with Japanese encephalitis: a case-control study. Lancet 2005;366:1375-1378
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   Ravi V, Desai A, Balaji M, et al. Development and evaluation of a rapid IgM capture ELISA (JEV-Chex) for the diagnosis of Japanese encephalitis. J Clin Virol 2006;35:429-434
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Citing Articles (5)

Citing Articles

1. 1

   Jiu-Song Zhang, Qiu-Min Zhao, Shu-Qing Zuo, Na Jia, Xiao-Fang Guo. (2012) Cytokine and chemokine responses to Japanese encephalitis live attenuated vaccine in a human population. International Journal of Infectious Diseases
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2. 2

   Scott B Halstead, Stephen J Thomas. (2011) New Japanese encephalitis vaccines: alternatives to production in mouse brain. Expert Review of Vaccines 10:3, 355-364
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3. 3

   Tomohiro Ishikawa, Eiji Konishi. (2010) Combating Japanese encephalitis: Vero-cell derived inactivated vaccines and the situation in Japan. Future Virology 5:6, 785-799
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4. 4

   A Wilder-Smith, SB Halstead. (2010) Japanese encephalitis: update on vaccines and vaccine recommendations. Current Opinion in Infectious Diseases 23:5, 426-431
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5. 5

   Scott B. Halstead, Stephen J. Thomas. (2010) New Vaccines for Japanese Encephalitis. Current Infectious Disease Reports 12:3, 174-180
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