Japanese encephalitis primary prevention
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
The control of Japanese encephalitis is based essentially on three interventions: mosquito control, avoiding human exposure to mosquitoes and immunization. Mosquito control has been very difficult to achieve in rural settings and avoidance of exposure is difficult as Culex mosquitoes bite during day time. Immunization is the only effective method for sustainable control. Routine immunization of school-age children is currently in use in Korea, Japan, China, Thailand and Taiwan. The introduction of the JE vaccine into the Expanded Program of Immunization has helped curb the disease in countries like Thailand, Vietnam, Sri Lanka and China[1].
Primary Prevention
- Use insect repellent and wear long pants and sleeves
- Sleep in air-conditioned or well-screened rooms or use bednets
- A vaccine against JE virus is available.
Vaccine
Infection with Japanese encephalitis virus confers life-long immunity. All current vaccines are based on the genotype III virus. Among the currently available vaccines is a formalin-inactivated vaccine derived from mouse brain-grown JEV strain Nakayama[2][3] , which still is produced by manufacturers in Korea, Thailand and Vietnam. It was first produced in Japan in the 1930s and was validated for use in Taiwan in the 1960s and in Thailand in the 1980s. The widespread use of vaccine and urbanisation has led to control of the disease in Japan, Korea, Taiwan and Singapore. The high cost of the vaccine, which is grown in live mice, means that poorer countries have not been able to afford to give it as part of a routine immunization program. The vaccine requires three doses on days 0, 7 and 30, followed by a booster at 1 year and thereafter at intervals of 3 years. The vaccine can often generate neurological adverse reactions. In addition to local and systemic side effects, individual cases of generalized urticaria and angioedema were reported in about 1 case per 1000 vaccinees after vaccination of travelers from western countries.
Inactivated Vaccines
Another formalin-inactivated JE vaccine is prepared in China using the JEV P3 strain propagated in primary hamster kidney cell cultures. The vaccine appears to be more immunogenic than that based on the Nakayama strain and can be integrated into the routine childhood immunization schedule but is not distributed outside of China. It is now largely being replaced by the live attenuated vaccine.
In the UK, the two vaccines used (but which are unlicensed) are JE-Vax® and Green Cross. Three doses are given at 0, 7–14 and 28–30 days. The dose is 1ml for children and adult, and 0.5ml for infants under 36 months of age.
Several attempts are in progress to prepare inactivated JEV vaccines starting from virus grown in controlled cell line cultures. Several manufacturers are developing Vero cell-derived purified inactivated JE vaccines, either using the virulent Nakayama strain, as done by Japanese manufacturers, or starting from the attenuated SA14-14-2 JEV strain, as done by the Austrian biotech company Intercell. Phase I and Phase II clinical trials have shown that the vaccine was safe and immunogenic[4] and a Phase III trial was recently completed[5] . The Japanese vaccine candidates have been recently licensed in Japan, while the Intercell vaccine, Ixiaro, was licensed by the US FDA for adults. A two-dose rapid immunization schedule has been worked up for administration to travelers. Most people immunized with the Intercell vaccine developed protective neutralizing antibody levels that lasted for at least one year[6][7] and the vaccine was well tolerated [8] [9]. The company pursues a separate clinical development for pediatric indication for endemic countries in a joint venture with Biological E, an Indian manufacturer. A large pediatric Phase IIb trial is currently taking place in endemic settings in India. Similarly, a Vero cell inactivated vaccine is now being produced in China by the Beijing Institute of Biological Products.
The most common adverse effects are redness and pain at the injection site. Uncommonly, an urticarial reaction can develop about four days after injection. Because the vaccine is produced from mouse brain, there is a risk of autoimmune neurological complications of around 1 per million vaccinations.
Live Attenuated Vaccines
The live attenuated JE vaccine strain, SA14-14-2, which was obtained after 11 passages in weaning mice followed by 100 passages in primary hamster kidney cells, has been developed and used in China since 1988. The vaccine, which is produced by the Chengdu Institute of Biological Products in China, was licensed in recent years in several Asian countries and was extensively used from 2006 to 2008 in mass immunization campaigns in India. Although the product is not WHO prequalified at this time, much investment and efforts have been made to bring the production and quality control to international standards. The vaccine is produced on primary hamster kidney cells, lyophilized, and administered to children at one year of age and again at two years, in annual spring campaigns[10] . Initial observational studies in southern China involving more than 200,000 children had demonstrated the vaccine safety, immunogenicity (99-100% seroconversion rate in nonimmune subjects) and protective efficacy over 5 years[3]. The short-term effectiveness of a single dose of SA14-2-14 was demonstrated in 2001 in a case control study on Nepalese children where an efficacy of 99.3% was reported[11] . A five year follow-up study found the single-dose efficacy was maintained at 96.2%[12] . Another five-year follow up study showed that neutralizing antibody persistence was close to 90% at 4 years and 64% at 5 years after a single-dose of the vaccine in adult volunteers[13]. Recent studies in the Philippines have demonstrated the safety and efficacy of the vaccine even when co-administered with measles vaccine at 9 months of age. Similar studies in Sri Lanka and Indonesia will help confirm these findings in other Asian settings.
Currently, more than 30 million doses of the live SA14-2-14 vaccine are distributed annually in southern and western China and exported to Nepal, India and Korea. Starting in May 2006, the SA14-2-14 live attenuated vaccine was used in India to vaccinate 9.3 million children in 11 districts scattered among 4 states where JE was considered as highly endemic. More than 500 adverse events were reported during the campaign, including 66 severe AE, of which 22 were fatal. These cases were reviewed by an expert committee which concluded that none of the deaths were attributable to the vaccine. The severe adverse events and critical press coverage nevertheless had a deep negative impact on vaccine acceptance in the rest of the country, highlighting the need for proper safety monitoring and case investigations.
Chimeric Vaccines
A promising approach for a future JE vaccine has been the construction of a YF-JE chimera based on the attenuated 17D YF virus genome, in which the YFV sequences encoding viral structural proteins prM and E were replaced by the corresponding prM and E sequences from JEV strain SA14-2-14. The resulting YF-JE chimeric virus, ChimeriVax-JETM, developed by Acambis and now licensed to Sanofi Pasteur, was grown on Vero cells and shown to elicit JEV neutralizing antibodies as well as protection against nasal and intracerebral virus challenge in rhesus monkeys[14] [15][16]. The vaccine was tested in human adult volunteers in the USA, showing good safety and immunogenicity, with 94% of the vaccinees in the Phase II trial developing protective neutralizing antibody levels after a single dose[17] . The chimeric virus was shown not to replicate in mosquitoes which were fed the Chimerivax-JE vaccine[18], a further proof of attenuation. The vaccine has been undergoing Phase III clinical trials in the USA and Australia for adult indication, whereas a parallel pediatric development program has been launched in Thailand by SanofiPasteur.
Live Recombinant JEV Vaccines
Replication-defective canarypox (ALVAC) and the highly attenuated vaccinia virus strain NYVAC were used as vectors to express the pr-M, E, NS1 and NS2a gene from JEV. The vaccine candidates were found to be well tolerated but their immunogenicity was too weak, especially in non-vaccinia immune volunteers, to warrant further development[19].
Vaccination in Population at Risk
Neutralising antibody persists in the circulation for at least two to three years, and perhaps longer.[20][21] The total duration of protection is unknown, but because there is no firm evidence for protection beyond three years, boosters are recommended every two years for people who remain at risk.
- U.S. Expatriates: Japanese encephalitis vaccine is recommended for persons who plan to reside in areas where Japanese encephalitis is endemic or epidemic (residence during a transmission season). Risk for acquiring Japanese encephalitis is highly variable within the endemic regions. The incidence of Japanese encephalitis in the location of intended residence, the conditions of housing, nature of activities, and the possibility of unexpected travel to high-risk areas are factors that should be considered in the decision to seek vaccination.
- Travelers: JE vaccine is recommended for travelers who plan to spend at least 1 month in endemic areas during the JE virus transmission season. Vaccine should also be considered for the following:
- Short-term (less than 1 month) travelers to endemic areas during the transmission season, if they plan to travel outside an urban area and their activities will increase the risk of exposure. Higher-risk activities include participating in extensive outdoor activities (such as camping, hiking, trekking, biking, fishing, hunting, or farming) and staying in accommodations without air conditioning, screens, or bed nets.
- Travelers to an area with an ongoing outbreak.
- Travelers to endemic areas who are uncertain of specific travel destinations, activities, or duration.
References
- ↑ Tauber E, Dewasthaly S (2008). "Japanese encephalitis vaccines--needs, flaws and achievements". Biol Chem. 389 (5): 547–50. PMID 18953721.
- ↑ Chambers TJ, Tsai TF, Pervikov Y, Monath TP (1997). "Vaccine development against dengue and Japanese encephalitis: report of a World Health Organization meeting". Vaccine. 15 (14): 1494–502. PMID 9330458.
- ↑ 3.0 3.1 Monath TP (2002). "Japanese encephalitis vaccines: current vaccines and future prospects". Curr Top Microbiol Immunol. 267: 105–38. PMID 12082985.
- ↑ Sugawara K, Nishiyama K, Ishikawa Y, Abe M, Sonoda K, Komatsu K; et al. (2002). "Development of Vero cell-derived inactivated Japanese encephalitis vaccine". Biologicals. 30 (4): 303–14. PMID 12421588.
- ↑ Schuller E, Klade CS, Wölfl G, Kaltenböck A, Dewasthaly S, Tauber E (2009). "Comparison of a single, high-dose vaccination regimen to the standard regimen for the investigational Japanese encephalitis vaccine, IC51: a randomized, observer-blind, controlled Phase 3 study". Vaccine. 27 (15): 2188–93. doi:10.1016/j.vaccine.2008.12.062. PMID 19200452.
- ↑ Lyons A, Kanesa-thasan N, Kuschner RA, Eckels KH, Putnak R, Sun W; et al. (2007). "A Phase 2 study of a purified, inactivated virus vaccine to prevent Japanese encephalitis". Vaccine. 25 (17): 3445–53. doi:10.1016/j.vaccine.2006.12.046. PMID 17241714.
- ↑ Schuller E, Jilma B, Voicu V, Golor G, Kollaritsch H, Kaltenböck A; et al. (2008). "Long-term immunogenicity of the new Vero cell-derived, inactivated Japanese encephalitis virus vaccine IC51 Six and 12 month results of a multicenter follow-up phase 3 study". Vaccine. 26 (34): 4382–6. doi:10.1016/j.vaccine.2008.05.081. PMID 18599165.
- ↑ Tauber E, Kollaritsch H, Korinek M, Rendi-Wagner P, Jilma B, Firbas C; et al. (2007). "Safety and immunogenicity of a Vero-cell-derived, inactivated Japanese encephalitis vaccine: a non-inferiority, phase III, randomised controlled trial". Lancet. 370 (9602): 1847–53. doi:10.1016/S0140-6736(07)61780-2. PMID 18061060.
- ↑ Tauber E, Kollaritsch H, von Sonnenburg F, Lademann M, Jilma B, Firbas C; et al. (2008). "Randomized, double-blind, placebo-controlled phase 3 trial of the safety and tolerability of IC51, an inactivated Japanese encephalitis vaccine". J Infect Dis. 198 (4): 493–9. doi:10.1086/590116. PMID 18588481.
- ↑ Woods DL (1992). "Resuscitation of the newborn infant". Nurs RSA. 7 (1): 21–3, 26. PMID 1569999.
- ↑ Ohrr H, Tandan JB, Sohn YM, Shin SH, Pradhan DP, Halstead SB (2005). "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. 366 (9494): 1375–8. doi:10.1016/S0140-6736(05)67567-8. PMID 16226615.
- ↑ Tandan JB, Ohrr H, Sohn YM, Yoksan S, Ji M, Nam CM; et al. (2007). "Single dose of SA 14-14-2 vaccine provides long-term protection against Japanese encephalitis: a case-control study in Nepalese children 5 years after immunization. drjbtandan@yahoo.com". Vaccine. 25 (27): 5041–5. doi:10.1016/j.vaccine.2007.04.052. PMID 17521781.
- ↑ Sohn YM, Tandan JB, Yoksan S, Ji M, Ohrr H (2008). "A 5-year follow-up of antibody response in children vaccinated with single dose of live attenuated SA14-14-2 Japanese encephalitis vaccine: immunogenicity and anamnestic responses". Vaccine. 26 (13): 1638–43. doi:10.1016/j.vaccine.2008.01.021. PMID 18294743.
- ↑ Wienker TF, von Reutern GM, Ropers HH (1979). "Progressive myoclonus epilepsy. A variant with probable X-linked inheritance". Hum Genet. 49 (1): 83–9. PMID 112032.
- ↑ Monath TP, Soike K, Levenbook I, Zhang ZX, Arroyo J, Delagrave S; et al. (1999). "Recombinant, chimaeric live, attenuated vaccine (ChimeriVax) incorporating the envelope genes of Japanese encephalitis (SA14-14-2) virus and the capsid and nonstructural genes of yellow fever (17D) virus is safe, immunogenic and protective in non-human primates". Vaccine. 17 (15–16): 1869–82. PMID 10217584.
- ↑ Beasley DW, Li L, Suderman MT, Guirakhoo F, Trent DW, Monath TP; et al. (2004). "Protection against Japanese encephalitis virus strains representing four genotypes by passive transfer of sera raised against ChimeriVax-JE experimental vaccine". Vaccine. 22 (27–28): 3722–6. doi:10.1016/j.vaccine.2004.03.027. PMID 15315852.
- ↑ Monath TP, Guirakhoo F, Nichols R, Yoksan S, Schrader R, Murphy C; et al. (2003). "Chimeric live, attenuated vaccine against Japanese encephalitis (ChimeriVax-JE): phase 2 clinical trials for safety and immunogenicity, effect of vaccine dose and schedule, and memory response to challenge with inactivated Japanese encephalitis antigen". J Infect Dis. 188 (8): 1213–30. doi:10.1086/378356. PMID 14551893.
- ↑ Reid M, Mackenzie D, Baron A, Lehmann N, Lowry K, Aaskov J; et al. (2006). "Experimental infection of Culex annulirostris, Culex gelidus, and Aedes vigilax with a yellow fever/Japanese encephalitis virus vaccine chimera (ChimeriVax-JE)". Am J Trop Med Hyg. 75 (4): 659–63. PMID 17038690.
- ↑ Kanesa-thasan N, Smucny JJ, Hoke CH, Marks DH, Konishi E, Kurane I; et al. (2000). "Safety and immunogenicity of NYVAC-JEV and ALVAC-JEV attenuated recombinant Japanese encephalitis virus--poxvirus vaccines in vaccinia-nonimmune and vaccinia-immune humans". Vaccine. 19 (4–5): 483–91. PMID 11027812.
- ↑ Gambel JM, DeFraites R, Hoke C; et al. (1995). "Japanese encephalitis vaccine: persistence of antibody up to 3 years after a three-dose primary series (letter)". J Infect Dis. 171: 1074.
- ↑ Kurane I, Takashi T (2000). "Immunogenicity and protective efficacy of the current inactivated Japanese encephalitis vaccine against different Japanese encephalitis virus strains". Vaccine. 18 Suppl: 33&ndash, 5.