Live Attenuated Japanese Encephalitis Vaccine Research Articles

Investigating Nonspecific Effects of the Live-Attenuated Japanese Encephalitis Vaccine on Lower Respiratory Tract Infections in Children Aged 25-35 Months: Retrospective Cohort Study.

Live attenuated vaccines may be used to prevent nontargeted diseases such as lower respiratory tract infections (LRTIs) due to their nonspecific effects (NSEs). We aimed to analyze the NSEs of the Japanese encephalitis vaccine on pediatric LRTIs in children aged 25 months to 35 months. A retrospective cohort study was conducted by using a population-based electronic health record database in Zhejiang, China. Enrolled participants were children born from January 1, 2017, to December 31, 2017, and who were inoculated with the live-attenuated Japanese encephalitis vaccine (JE-L) or inactivated Japanese encephalitis vaccine (JE-I) as the most recent vaccine at 24 months of age. The study was carried out between January 1, 2019, and December 31, 2019. All inpatient and outpatient hospital visits for LRTIs among children aged 25 months to 35 months were recorded. The Andersen-Gill model was used to assess the NSEs of JE-L against LRTIs in children and compared with those of JE-I as the most recent vaccine. A total of 810 children born in 2017 were enrolled, of whom 585 received JE-L (JE-L cohort) and 225 received JE-I (JE-I cohort) as their last vaccine. The JE-L cohort showed a reduced risk of LRTIs (adjusted hazard ratio [aHR] 0.537, 95% CI 0.416-0.693), including pneumonia (aHR 0.501, 95% CI 0.393-0.638) and acute bronchitis (aHR 0.525, 95% CI 0.396-0.698) at 25 months to 35 months of age. The NSEs provided by JE-L were especially pronounced in female children (aHR 0.305, 95% CI 0.198-0.469) and children without chronic diseases (aHR 0.553, 95% CI 0.420-0.729), without siblings (aHR 0.361, 95% CI 0.255-0.511), with more than 30 inpatient and outpatient hospital visits prior to 24 months of age (aHR 0.163, 95% CI 0.091-0.290), or with 5 to 10 inpatient and outpatient hospital visits due to infectious diseases prior to 24 months old (aHR 0.058, 95% CI 0.017-0.202). Compared with JE-I, receiving JE-L as the most recent vaccine was associated with lower risk of inpatient and outpatient hospital visits for LRTIs among children aged 25 months to 35 months. The nature of NSEs induced by JE-L should be considered for policymakers and physicians when recommending JE vaccines to those at high risk of infection from the Japanese encephalitis virus.

Japanese Encephalitis Vaccine Acceptance and Strategies for Travelers: Insights from a Scoping Review and Practitioners in Endemic Countries.

Japanese encephalitis (JE) remains the cause of vaccine-preventable encephalitis in individuals living in endemic areas and international travelers. Although rare, the disease's high fatality rate emphasizes the need for effective immunization. This review aims to provide updated data on the JE burden between 2017 and 2023, vaccine acceptance, and vaccine strategies for travelers. We prospectively identified studies, using MEDLINE and PubMed, published through 2023. JE incidence has decreased in local populations and remains low among travelers from non-endemic countries. The local JE risk cannot be utilized to determine traveler risk. Adult travelers naïve to JEV infection or immunization may be at potentially higher risk. The JE vaccine acceptance rates among international travelers visiting JE endemic areas range from 0.2% to 28.5%. The cost of the vaccine and low risk perception could be barriers to JE vaccination. For travelers, an accelerated two-dose regimen of inactivated Vero cell JE vaccine (JE-VC) or a single dosage of live attenuated JE vaccine (JE-LV) may be an option. In conclusion, the JE burden among residents and travelers is lower, but the risk is not negligible. Practitioners should prioritize sharing knowledge, increasing awareness, and promoting vaccinations and preventive measures to reduce tourists' risk of JE along their journey.

Live-attenuated Japanese encephalitis virus inhibits glioblastoma growth and elicits potent antitumor immunity.

Glioblastomas (GBMs) are highly aggressive brain tumors that have developed resistance to currently available conventional therapies, including surgery, radiation, and systemic chemotherapy. In this study, we investigated the safety of a live attenuated Japanese encephalitis vaccine strain (JEV-LAV) virus as an oncolytic virus for intracerebral injection in mice. We infected different GBM cell lines with JEV-LAV to investigate whether it had growth inhibitory effects on GBM cell lines in vitro. We used two models for evaluating the effect of JEV-LAV on GBM growth in mice. We investigated the antitumor immune mechanism of JEV-LAV through flow cytometry and immunohistochemistry. We explored the possibility of combining JEV-LAV with PD-L1 blocking therapy. This work suggested that JEV-LAV had oncolytic activity against GBM tumor cells in vitro and inhibited their growth in vivo. Mechanistically, JEV-LAV increased CD8+ T cell infiltration into tumor tissues and remodeled the immunosuppressive GBM microenvironment that is non-conducive to immunotherapy. Consequently, the results of combining JEV-LAV with immune checkpoint inhibitors indicated that JEV-LAV therapy improved the response of aPD-L1 blockade therapy against GBM. The safety of intracerebrally injected JEV-LAV in animals further supported the clinical use of JEV-LAV for GBM treatment.

Immunogenicity and safety of an inactivated enterovirus 71 vaccine co-administered with measles-mumps-rubella vaccine and live-attenuated Japanese encephalitis vaccine: a phase 4, single-center, randomized controlled trial

ABSTRACT Co-administration of vaccines could be an efficient strategy to increase vaccination uptake and reduce the number of clinic visits. This randomized controlled study aimed to evaluate the immunogenicity and safety of enterovirus 71 (EV71) vaccine co-administered with measles-mumps-rubella (MMR) vaccine and live-attenuated Japanese encephalitis vaccine (LA-JEV). A total of 372 healthy infants were randomly assigned in a 1:1:1 ratio to receive simultaneous administration of EV71 vaccine (dose 1) and MMR on d 0 and EV71 vaccine (dose 2) and LA-JEV on d 30 (Group 1); administration of MMR and LA-JEV on d 0 and 30, respectively (Group 2); or administration of doses 1 and 2 of EV71 vaccine on d 0 and 30, respectively (Group 3). The non-inferiority analysis of the seroconversion for EV71 neutralizing antibody after vaccination was the primary outcome. According to per protocol set, antibody response against EV71, measles, mumps, rubella, and Japanese encephalitis (JE) virus was similar regardless of administration schedule. After vaccination, the seroconversion rate of EV71 neutralizing antibody in Group 1 (107 [97.27%] of 110) was non-inferior to that in Group 3 (109 [97.32%] of 112; difference – 0.05% [95% CI – 5.38 to 5.21]). The incidences of adverse reactions were 62.60% (77/123) in Group 1, 54.84% (68/124) in Group 2, and 37.70% (46/122) in Group 3, and most of them were mild to moderate in severity. No vaccine-related serious adverse events were reported. In total, the co-administration of combined EV71 vaccine with MMR and LA-JEV showed no interference with antibody response and demonstrated good safety profiles.

Immunogenicity and Protective Ability of Genotype I-Based Recombinant Japanese Encephalitis Virus (JEV) with Attenuation Mutations in E Protein against Genotype V JEV.

Genotype V (GV) Japanese encephalitis virus (JEV) has emerged in Korea and China since 2009. Recent findings suggest that current Japanese encephalitis (JE) vaccines may reduce the ability to induce neutralizing antibodies against GV JEV compared to other genotypes. This study sought to produce a novel live attenuated JE vaccine with a high efficacy against GV JEV. Genotype I (GI)-GV intertypic recombinant strain rJEV-EXZ0934-M41 (EXZ0934), in which the E region of the GI Mie/41/2002 strain was replaced with that of GV strain XZ0934, was introduced with the same 10 attenuation substitutions in the E region found in the live attenuated JE vaccine strain SA 14-14-2 to produce a novel mutant virus rJEV-EXZ/SA14142m-M41 (EXZ/SA14142m). In addition, another mutant rJEV-EM41/SA14142m-M41 (EM41/SA14142m), which has the same substitutions in the Mie/41/2002, was also produced. The neuroinvasiveness and neurovirulence of the two mutant viruses were significantly reduced in mice. The mutant viruses induced neutralizing antibodies against GV JEV in mice. The growth of EXZ/SA14142m was lower than that of EM41/SA14142m. In mouse challenge tests, a single inoculation with a high dose of the mutants blocked lethal GV JEV infections; however, the protective efficacy of EXZ/SA14142m was weaker than that of EM41/SA14142m in low-dose inoculations. The lower protection potency of EXZ/SA14142m may be ascribed to the reduced growth ability caused by the attenuation mutations.

Immunogenicity and safety of concomitant inoculation of Measles and rubella combined live vaccine and Japanese encephalitis attenuated live vaccine

Objective: To evaluate the immunogenicity and safety of concomitant inoculation of Measles and Rubella Combined Live-attenuated Japanese encephalitis vaccine. Methods: Healthy children aged 8 months in selected cities in Zhejiang Province were randomly assigned to the MR and JVE-L combined vaccination group (the experimental group), and the MR single vaccination group (the control group) was taken before the exemption and 6 weeks after the exemption. Peripheral venous blood 1 ml was used as serum antibody test for measles and rubella, and the levels of measles and rubella antibodies before and after vaccination were evaluated. The safety of combined vaccination was evaluated. Measles and rubella IgG antibodies were detected by enzyme-linked immunosorbent assay (ELISA). Data were double-entry with Epidata and statistical analysis was performed using Epi Info epidemiological statistical analysis software. Results: The results showed that no severe adverse event occurred in two groups, clinical reactions in each inoculation group were mild.The seroconversion rate of measles antibody and rubella antibody were 96.43% and 88.49% in the experimental group after vaccination, the geometrical mean concentrations(GMC) of measles antibody was 1 526.45 mIU/ml and the GMC of rubella antibody was 47.70 mIU/ml after concomitant inoculation; the seroconversion rate of measles antibody and rubella antibody were 97.62% and 86.11% in the control group, the GMC of Measles antibody was 1 392.28 mIU/ml and the GMC of Rubella antibody was 45.72 mIU/ml after MV inoculation. No difference were detected in two groups of seroconversion rate of measles antibody and rubella antibody and GMC after vaccination. Conclusion: The immunogenicity and safety is equivalent when MR and JVE-L were simultaneous inoculation.

Effectiveness of the SA 14-14-2 Live-Attenuated Japanese Encephalitis Vaccine in Myanmar.

Myanmar is an endemic country for the Japanese encephalitis virus (JEV), and the SA-14-14-2 live-attenuated JEV vaccine was first introduced as a catch-up vaccination campaign in 2017. To determine the effectiveness of vaccination by means of neutralizing antibody titers against JEV, a cross-sectional descriptive study was conducted among five to 15-year-old monastic school children in Mandalay, Myanmar. A total of 198 students who had received vaccines were recruited, and single-time investigation of anti-JEV IgG and neutralizing antibodies against wild-type JEV were determined using anti-JEV IgG ELISA and plaque reduction neutralization tests (PRNT50). All students 100% (198/198) showed positive results on the anti-JEV IgG ELISA, and 87% (172/198) of the students had neutralizing antibodies against JEV six months after immunization. The geometric mean titers of both IgG antibodies and neutralizing antibodies increased with the participants’ age groups, and statistically significant differences in anti-JEV IgG titers were noted across age groups. In this study, we could not investigate the persistence of neutralizing antibodies as only single-time blood collection was done. This study, which is the first report of JEV vaccination among children in Myanmar, showed similar neutralizing antibody production rates among vaccinated individuals as did studies in other countries.

Feasibility of chitosan-based nanoparticles approach for intranasal immunisation of live attenuated Japanese encephalitis vaccine

Intranasal (IN) administration, a non-invasive route, is explored to overcome the limitations of conventional subcutaneous (SC) injection for Japanese encephalitis (JE) immunisation. Mucoadhesive nanoparticles (NPs) are recognised for the benefits they offer via IN delivery, such as extended retention time of the vaccine on the mucosa. The purpose of this study was to evaluate immunisation effect of live attenuated Japanese encephalitis-chimeric virus vaccine (JE-CV)-loaded mucoadhesive NPs based on chitosan (CS) or chitosan maleimide (CM), a novel mucoadhesive polymer, via the IN route to improve the mucosal immunisation against JE. The results revealed that IN immunisation stimulated seroprotection following PRNT50 evaluation. Moreover, compared with SC immunisation, IN immunisation in mice provided a higher sIgA level, leading to improved mucosal immune response. In addition, chitosan-based NPs showed an adjuvant effect on the IN vaccine due to their mucoadhesive and antigen-uptaken properties. CM NPs successfully induced sIgA. In contrast, SC JE-CV immunisation induced negligible mucosal immunity. These immunological advantages revealed that JE-CV-loaded mucoadhesive NPs are a promising approach for IN vaccination as an alternative route for JE protection due to the stimulatory effects on both mucosal and systemic immune responses.

Effectiveness of Japanese encephalitis vaccine SA 14-14-2 and impact of immunization among adults in Assam, India

Background: Japanese encephalitis (JE) is the leading cause of viral encephalitis in India. Assam contributes 2.5% of the country's population, contributing to ∼36% of JE case-load. Vaccination is the only preventive measure available to combat the disease. Live attenuated JE vaccine, SA 14-14-2 is the most widely used JE vaccine in the Asian sub-continent. JE was earlier known as the disease of children. Thus, to combat the disease among the pediatric age-group, the Government of India (GoI) undertook a mass JE vaccination program in campaign mode during 2006 among children (1–15 years). Interestingly, a rising trend of JE among adults became conspicuous since 2007. In response, GoI undertook mass JE vaccination drive among adults in the worst JE affected district of Assam, Sivasagar, on a pilot basis in 2011. Another vaccination drive was carried out in 2014 to cover the missed out adult population. The present study aimed at evaluating vaccine effectiveness (VE) of a single dose of SA 14-14-2 up to seven years post-vaccination and understanding the impact of immunization among adults in Sivasagar. Methods and materials: During 2012–2018, a case-control study was conducted recruiting 261 JE cases and 522 age-sex matched healthy controls. VE was calculated based on the odds ratio. Incidence rate (IR) per 100,000 population during pre (2009–2011) and post-vaccination periods (2012–2018) were compared to assess the impact of immunization. Results: VE among adults was 90% in 2012; it gradually declined to 82% in 2013. Following the second round of vaccination in 2014, a marginal increase in VE was noted (84%). Subsequently (2015–2018), VE stabilized at ∼70%. IR during the pre-vaccination period was 11.5 that came down and maintained at ∼5 (post-vaccination). Vaccine coverage among controls was 39%. Conclusion: In Nepal, the same vaccine showed 96.2% VE among children (5 years’ post-vaccination) with coverage of above 70% that brought down IR <1. Therefore, high vaccine coverage (at least 70%) seems to be a prerequisite for achieving the desired results. As adults are highly mobile population, proper planning and sensitization prior to mass vaccination drive are of paramount importance to get a sizeable population covered.

Persistence of IgM Antibodies after Vaccination with Live Attenuated Japanese Encephalitis Vaccine.

.Japanese encephalitis (JE) is a vaccine-preventable, mosquito-borne disease. Substantial progress with JE control in Asia has been made during the past decade, with most endemic countries now having JE vaccination programs, commonly using live attenuated SA14-14-2 JE vaccine (trade name CD-JEV). If a child develops encephalitis during the weeks to months following CD-JEV vaccination and anti-JE virus IgM (JE IgM) antibody is detected in serum, the question arises if this is JE virus infection indicating vaccine failure, or persistent JE IgM antibody postvaccination. To better understand JE IgM seropositivity following vaccination, sera from 268 children from a previous CD-JEV study were tested by two different JE IgM assays to determine JE IgM antibody frequency on days 28, 180, and 365 postvaccination. With the CDC JE IgM antibody capture ELISA (MAC-ELISA), 110 children (41%) had JE IgM positive or equivocal results on their day 28 sample, and eight (3%) and two (1%) had positive or equivocal results on day 180 and day 365 samples, respectively. With the InBios JE Detect™ MAC-ELISA (Seattle, WA), 118 (44%) children had positive or equivocal results on day 28 sample, and three (1%) and one (0.4%) had positive or equivocal results on day 180 and day 365 samples, respectively. Our results indicate that more than 40% children vaccinated with CD-JEV can have JE IgM antibodies in their serum at 1 month postvaccination but JE IgM antibody is rare by 6 months. These data will help healthcare workers assess the likelihood that JE IgM antibodies in the serum of a child with encephalitis after vaccination are vaccine related.

Immunogenicity and safety of two-visit, intradermal pre-exposure rabies prophylaxis simultaneously administrated with chimeric live-attenuated Japanese encephalitis vaccine in children living in rabies and Japanese encephalitis endemic country

BackgroundReducing the number of doses required for pre-exposure prophylaxis (PrEP) would make it more feasible and cost-effective to implement in children at the highest risk of rabies exposure in Asia. We studied immune response of 2-site intradermal (ID) injection of rabies vaccine on days 0 and 28 for rabies PrEP simultaneously administrated with live-attenuated Japanese encephalitis chimeric virus vaccine (JE-CV) for children living in endemic area. Research design and methodsSeronegative children (n = 49) aged 12–16 months were randomized 2:1 into two groups: Group A subjects were vaccinated with 0.1-mL ID injection of purified Vero cell rabies vaccine (PVRV), each at two sites on day (D) 0 and D28; Group B subjects were vaccinated with conventional 0.5-mL intramuscular PVRV on D0, D7 and D28. Both groups received one dose of JE-CV subcutaneously on D0 and D365. Rabies virus neutralizing antibody (RVNA) titers were measured on D0, D42 and D365 after vaccination; Japanese Encephalitis (JE) neutralizing antibody titers were determined on D0, D42, D365 and D379. ResultsAll children had RVNA ≥ 0.5 IU/mL on D42 (geometric mean titers [GMTs] of RVNA 14.35 IU/mL [Group A] and 14.83 IU/mL [Group B], p > 0.05]). On D365, RVNA GMTs of subjects in group A and B were 1.50 IU/mL and 2.00 IU/mL (p > 0.05), respectively. All children had seroprotection following booster dose of JE-CV. There were no vaccine-related SAEs observed. ConclusionThe 2-site ID PrEP with PVRV on days 0 and 28 co-administrated with JE-CV are safe and immunogenic.

Communication and awareness on a new vaccine: a cross-sectional study in a tertiary care hospital of West Bengal

Background: Japanese encephalitis (JE) vaccination in India started in 2006 with SA-14-14-2 live attenuated JE vaccine (JEV) following large outbreaks of JE in some districts of Eastern Uttar Pradesh and Bihar in 2005. Age groups 1-15 yrs are first vaccinated with a single dose of JEV in a campaign mode followed by integration of this vaccine in routine immunization. It is beyond doubt that added to vaccination campaigns, proper awareness on JE can play significant role in controlling the disease.Methods: An observational study with cross sectional design was conducted in Kolkata Medical College and Hospital, Kolkata during JE Vaccination campaign during January, 2018 among 85 respondents, to assess the awareness on JE, among care-givers who brought their children for vaccination at the immunization clinic.Results: It was found that only 37.6% the respondents attending the campaign knew the name of the disease; 17.6% respondents were aware about disease transmission, and 5.9% could state two or more clinical features that might be associated with Japanese Encephalitis. 69.4% had no knowledge of up to what age JE vaccines can be administered; 23.5% said it can be administered till the beneficiaries attain fifteen years of age.Conclusions: IEC activities during JE vaccination campaign was not able raise awareness on JE to the desired level. However beneficiaries were informed about service availability and could be mobilised to come for vaccination.

Partial cross-protection between Japanese encephalitis virus genotype I and III in mice.

Genotype III (GIII) Japanese encephalitis virus (JEV) predominance has gradually been replaced by genotype I (GI) over the last 20 years in many Asian countries. This genotype shift raises concerns about the protective efficacy of Japanese encephalitis (JE) vaccines, as all of the currently licensed JE vaccines are derived from GIII strains. In this study, we conducted vaccination-challenge protection assays to evaluate the cross-protective efficacy of GI- or GIII-derived vaccines against the challenge of a heterologous genotype using a mouse challenge model. Titration of the neutralizing antibodies elicited by SA14-14-2 live-attenuated JE vaccine (SA14-14-2 vaccine), a GIII-derived vaccine, indicated that the titer of neutralizing antibodies specific to heterologous genotype GI stain was significantly lower than that specific to homologous genotype GIII strain in both pigs and mice immunized with the SA14-14-2 vaccine. Vaccination of mice with SA14-14-2 vaccine or a GIII-inactivated vaccine at high and medium doses completely protected vaccinated mice against challenge with the homologous genotype GIII strains, but failed to provide the vaccinated mice complete protection against the challenge of heterologous genotype GI strains. The protection rates against GI strain challenge were 60%–80%, showing that these vaccines were partially protective against GI strain challenge. Additionally, vaccination of mice with a GI-inactivated vaccine conferred 100% protection against the challenge of homologous genotype GI strains, but 50%–90% protection against the challenge of heterologous genotype GIII strains, showing a reduced protective efficacy of a GI-derived vaccine against GIII strain challenge. Overall, these observations demonstrated a partial cross-protection between GI and GIII strains and suggested a potential need for new JE vaccine strategies, including options like a bivalent vaccine, to control both genotype infection.

Molecular and clinical relationship between live-attenuated Japanese encephalitis vaccination and childhood onset myasthenia gravis.

ObjectiveThe incidence of childhood onset myasthenia gravis (CMG) in China is higher than that in other countries; however, the reasons for this are unclear.MethodsWe investigated the clinical and immunological profiles of CMG, and assessed the potential precipitating factors. For the mouse studies, the possible implication of vaccination in the pathogenesis was explored.ResultsIn our retrospective study, 51.22% of the 4,219 cases of myasthenia gravis (MG) were of the childhood onset type. The cohort study uncovered that the pathophysiology of CMG was mediated by immune deviation, rather than through gene mutations or virus infections. The administration of the live‐attenuated Japanese encephalitis vaccine (LA‐JEV), but not the inactivated vaccine or other vaccines, in mice induced serum acetylcholine receptor (AChR) antibody production, reduced the AChR density at the endplates, and decreased both muscle strength and response to repetitive nerve stimulation. We found a peptide (containing 7 amino acids) of LA‐JEV similar to the AChR‐α subunit, and immunization with a synthesized protein containing this peptide reproduced the MG‐like phenotype in mice.InterpretationOur results describe the immunological profile of CMG. Immunization with LA‐JEV induced an autoimmune reaction against the AChR through molecular mimicry. These findings might explain the higher occurrence rate of CMG in China, where children are routinely vaccinated with LA‐JEV, compared with that in countries, where this vaccination is not as common. Efforts should be made to optimize immunization strategies and reduce the risk for developing autoimmune disorders among children. Ann Neurol 2018;84:386–400

Post-marketing safety surveillance for inactivated and live-attenuated Japanese encephalitis vaccines in China, 2008–2013

IntroductionTwo types of Japanese encephalitis (JE) vaccines, inactivated JE vaccine (JE-I) and live-attenuated JE vaccine (JE-L), are available and used in China. In particular, one JE-L, produced by a domestic manufacturer in China, was prequalified by WHO in 2013. We assessed the safety of JE vaccines in China during 2008–2013 using the Chinese National Adverse Events Following Immunization Information System (CNAEFIS) data. MethodsWe retrieved AEFI reporting data about JE vaccines from CNAEFIS, 2008–2013, examined demographic characteristics of AEFI cases, and used administrative data on vaccine doses as denominator to calculate and compare crude reporting rates. We also used disproportionality reporting analysis between JE-I and JE-L to assess potential safety signals. ResultsA total of 34,879 AEFIs related with JE-I and JE-L were reported, with a ratio of male to female as 1.3:1; 361 (1.0%) cases were classified as serious. JE vaccines were administered concurrently with one or more other vaccines in 13,592 (39.0%) of cases. The overall AEFI reporting rates were 214.4 per million vaccination doses for JE-L and 176.9 for JE-I (rate ratio [RR]: 1.2, 95% confidence interval [CI]: 1.1–1.3) in 2010–2013. Febrile convulsions (FC) following JE-I was found as a signal of disproportionate reporting (SDR). However, there was no significant difference between the reporting rates of FC of JE-I and JE-L (0.3 per million vaccination doses for JE-L, 0.4 for JE-I, p=0.05). ConclusionsWhile our analysis did not find apparent safety concern of JE vaccines in China, further study should consider JE-I vaccines and febrile convulsion, and taking more sensitive methods to detect signals.

Safety of live attenuated Japanese encephalitis vaccine given at the age of 9 months in National Immunisation Programme of Sri Lanka.

This study was designed to describe the safety profile of the single dose live attenuated Japanese encephalitis vaccine (LJEV) SA-14-14-2 given at the age of 9 months in the National Immunisation programme of Sri Lanka. cohort event monitoring (CEM) was conducted in the Jaffna district during November 2012 to January 2015. A representative sample of 3041 infants who received the LJEV at the age of 9 months was followed up actively over telephone interviews on days 1, 3, 14, 30 and 45 for adverse events (AE). Parents were encouraged to self-report in between these interviews. When an AE is notified, further clinical information was obtained through in-depth interviews and home/hospital visits to determine as an adverse event following immunisation (AEFI). Investigators independently reviewed each AEFI for consistent causal association with LJEV according to WHO causality assessment. Of the 2878 (94%) infants who completed the follow up of 14 days, 911 (32%) experienced 1423 AEFIs. Of them, 376 (26%) were identified as AEFI with consistent causal association to LJEV (AEFIc). Irritability (53/ 1000 doses administered) and fever ≥100.4° F (46/1000 doses administered) accounted for 41% and 35% of AEFIcrespectively. Majority of AEFI (940) were identified as inconsistent as there were alternate causes. Nineteen AEFIc in 14 infants were classified as serious since they led to hospitalisation. Of the 2392 (79%) infants who completed 45 days follow up, 1022 experienced 1804 AEFI during 15-45 days. Only 20 were identified as AEFIc. There were no reported fatal or life threatening AEs. LJEV administered to infants at 9 months was devoid of any significant safety concerns as most of the AEFIs were non-serious and resolved completely. CEM is a useful method for AEFI surveillance.

Reemergence of Japanese Encephalitis in South Korea, 2010-2015.

To the Editor: Japanese encephalitis (JE) is caused by a virus transmitted by Culex tritaeniorhynchus mosquitoes. JE was the major public health concern in South Korea until the late 1960s, with several thousand cases reported annually. The national vaccination program with the inactivated mouse brain–derived Nakayama strain was initiated in 1983 and targeted children <15 years of age. During 1983–2000, annual booster vaccinations were given to children <15 years of age, but in 2000, the booster schedule was changed to 2 doses (1 dose each) for children 6 and 12 years of age. The live attenuated JE vaccine SA 14-14-2 was introduced in 2002 and included in the national immunization program in 2014. After introduction of the mandatory immunization program, JE was nearly eliminated; during most of the past 3 decades, <0.02 cases per 100,000 population have been reported annually (1). However, since 2010, JE has reemerged in South Korea. We describe epidemiologic data for JE, focusing on the recent increase in number of cases in South Korea. We accessed demographic information from the disease web statistics system provided by the Korea Centers for Disease Control and Prevention (2). Our study was exempted from review by the Institutional Review Board at Seoul National University Hospital (E-1602-053-739).

Sero-Molecular Epidemiology of Japanese Encephalitis in Zhejiang, an Eastern Province of China.

BackgroundSporadic Japanese encephalitis (JE) cases still have been reported in Zhejiang Province in recent years, and concerns about vaccine cross-protection and population-level immunity have been raised off and on within the public health sphere. Genotype I (GI) has replaced GIII as the dominant genotype in Asian countries during the past few decades, which caused considerable concerns about the potential change of epidemiology characteristics and the vaccine effectiveness. The aim of this study was to investigate the prevalence of JE neutralizing antibody and its waning antibody trend after live attenuated JE vaccine immunization. Additionally, this study analyzed the molecular characteristics of the E gene of Zhejiang Japanese encephalitis virus (JEV) strains, and established genetic relationships with other JEV strains.Methodology/Principal FindingsA total of 570 serum specimens were sampled from community population aged from 0 to 92 years old in Xianju county of Zhejiang Province in 2013–2014. Microseroneutralization test results were analyzed to estimate the population immunity and to observe antibody dynamics in vaccinated children. E genes of 28 JEV strains isolated in Zhejiang Province were sequenced for phylogenetic tree construction and molecular characteristics analysis with other selected strains. Positive JE neutralizing antibody rates were higher in residents ≥35 years old (81%~98%) and lower in residents <35 years old (0~57%). 7 or 8 years after the 2nd live attenuated vaccine dose, the antibodies against for 4 different strains with microseroneutralization test were decreased by 55%~73% on seropositive rates and by 25%~38% on GMTs respectively. JEV strains isolated in recent years were all grouped into GI, while those isolated in the 1980s belonged to GIII. On important amino acid sites related to antigenicity, there was no divergence between the Zhejiang JE virus strains and the vaccine strain (SA14-14-2).Conclusion/SignificancesJE neutralizing antibody positive rates increase in age ≥10 years old population, likely reflecting natural infection or natural boosting of immunity through exposure to wild virus. JE seropositivity rates were quite low in <35 years old age groups in Zhejiang Province. Waning of neutralizing antibody after live attenuated vaccine immunization was observed, but the clinical significance should be further investigated. Both the peripheral antibody response and genetic characterization indicate that current live attenuated JE vaccine conferred equal neutralizing potency against GI or GIII of wild strains. GI has replaced GIII as the dominant genotype in Zhejiang in the past few decades. Although the chance of exposure to wild JE virus has reduced, the virus still circulates in nature; therefore, it is necessary to implement immunization program for children continually and to conduct surveillance activity periodically.

Comparison of the live-attenuated Japanese encephalitis vaccine SA14 -14-2 strain with its pre-attenuated virulent parent SA14 strain: similarities and differences in vitro and in vivo

Japanese encephalitis virus (JEV) is the main cause of acute viral encephalitis, primarily affecting children and young adults in the Asia-Pacific region. JEV is a vaccine-preventable pathogen, with four types of JE vaccine licensed in different regions of the world. To date, the most common JEV strain used in vaccine development and production is SA14-14-2, an attenuated strain derived from its wild-type parental strain SA14. In this study, we directly compared the phenotypic and genotypic characteristics of SA14 and SA14-14-2 to determine the biological and genetic properties associated with their differential virulence. In susceptible BHK-21 cells, SA14-14-2 grew slightly more slowly and formed smaller plaques than SA14, but unlike SA14, it showed almost no expression of the viral protein NS1', the product of a conserved predicted RNA pseudoknot-mediated ribosomal frameshift. In weanling ICR mice, SA14-14-2 was highly attenuated in terms of both neuroinvasiveness and neurovirulence, with its median lethal doses invariably over five logs higher than those of SA14 when inoculated intramuscularly and intracerebrally. Interestingly, the neurovirulence of SA14-14-2 was dependent on mouse age, with the 1- to 7-day-old mice being highly susceptible and the 14- to 21-day-old mice becoming resistant to intracerebral inoculation. At the genome level, SA14-14-2 differed from SA14 by 57 nucleotides, including one silent G-to-A substitution at position 3599 within the predicted RNA pseudoknot for NS1' synthesis; of the 57 differences, 25 resulted in amino acid substitutions. Our data pave the way for the development of new genetically modified JE vaccines.

Cross-protective immunity against circulating Japanese encephalitis virus and West Nile Virus by live attenuated Japanese encephalitis vaccine SA 14-14-2

Cross-protective immunity against circulating Japanese encephalitis virus and West Nile Virus by live attenuated Japanese encephalitis vaccine SA 14-14-2