Japanese Encephalitis Vaccine Research Articles

Coverage of Second Dose of Measles-Containing Vaccine (MCV-2) and Japanese Encephalitis Vaccine (JE-2) and Its Predictors Among Children 2–5 Years Old in the Ormanjhi Block of Ranchi, Jharkhand, India: A Mixed Method Study

Coverage of Second Dose of Measles-Containing Vaccine (MCV-2) and Japanese Encephalitis Vaccine (JE-2) and Its Predictors Among Children 2–5 Years Old in the Ormanjhi Block of Ranchi, Jharkhand, India: A Mixed Method Study

5-year vaccine protection following a single dose of Vi-tetanus toxoid conjugate vaccine in Bangladeshi children (TyVOID): a cluster randomised trial

WHO currently recommends a single dose of typhoid conjugate vaccine (TCV) in high-burden countries based on 2-year vaccine efficacy data from large randomised controlled trials. Given the decay of immunogenicity, the protection beyond 2 years is unknown. We therefore extended the follow-up of the TyVAC trial in Bangladesh to assess waning of vaccine protection to 5 years after vaccination. We conducted a cluster randomised controlled trial (TyVAC; ISRCTN11643110) in Dhaka, Bangladesh, between 2018 and 2021. Children aged 9 months to 15 years were invited to receive a single dose of TCV or Japanese encephalitis vaccine between April 15, 2018, and November 16, 2019, based on the randomisation of their clusters of residence. Children who received the Japanese encephalitis vaccine were invited to receive TCV at the final visit between Jan 6, and Aug 31, 2021, according to the protocol. This follow-on study extended the follow-up of the original trial until Aug 14, 2023. The primary endpoint of this study was to compare the incidence of blood culture-confirmed typhoid between children who received TCV in 2018-19 (the previous-TCV group) and those who received the vaccine in 2021 (the recent-TCV group), to evaluate the relative decline in vaccine protection. We also did a nested study using the test-negative design comparing the recent-TCV and previous-TCV groups with unvaccinated individuals, as well as an immunogenicity study in a subset of 1500 children. Compared with the recent-TCV group, the previous-TCV group had an increased risk of typhoid fever between 2021-23, with an adjusted incidence rate ratio of 3·10 (95% CI 1·53 to 6·29; p<0·0001), indicating a decline in the protection of a single-dose of TCV 3-5 years after vaccination. The extrapolated vaccine effectiveness in years 3-5 was 50% (95% CI -13 to 78), and was validated using the test-negative design analysis, with a vaccine effectiveness of 84% (74 to 90) in the recent-TCV group and 55% (36 to 68) in the previous-TCV group, compared with unvaccinated individuals. Anti-Vi-IgG responses declined over the study period. The highest rate of decay was seen in children vaccinated at younger than 2 years in the original trial. The inverse correlation between age and the decay of antibodies was also seen in the subgroup analysis of vaccine effectiveness, where the youngest age group (<7 years at fever visits) exhibited the fastest waning, with vaccine effectiveness dropping to 24% (95% CI -29 to 55) at 3-5 years after vaccination. A decline in the protection conferred by a single-dose TCV was observed 3-5 years after vaccination, with the greatest decline in protection and immune responses observed in children vaccinated at younger ages. A booster dose of TCV around school entry age might be needed for children vaccinated while younger than 2 years to sustain protection against typhoid fever during the school years when the risk is the highest. The Bill & Melinda Gates Foundation.

ASSESSMENT OF JAPANESE ENCEPHALITIS VACCINATION STATUS IN TRIBAL AREAS OF THE MAYURBHANJ DISTRICT OF ODISHA – A COMMUNITY-BASED CROSS-SECTIONAL STUDY

Objectives: Japanese encephalitis (JE) is a vector-borne viral disease that primarily infects swines, equids, and humans. Outbreaks of JE-acute encephalitis syndrome were reported from September to November 2012 and 9th September to 2nd December 2016 in Malkangiri district, Odisha. Due to the paucity of studies on JE transmission, causation, and prevention in tribal areas, the present study was undertaken to assess the JE vaccination status of children between 12 and 36 months in the Mayurbhanj district and to determine the association between sociodemographic characteristics of study participants with JE vaccination status. Methods: To estimate the JE vaccination coverage, a cluster sampling method was adopted to conduct survey in the Mayurbhanj district of Odisha by selecting 45 clusters. Twenty children aged 12–36 months were selected from each cluster, and their mothers were interviewed about JE vaccination. House-to-house survey was conducted in selected villages. Mothers were interviewed about the knowledge on JE vaccination. Results: A total of 900 children were surveyed, of which a majority were born in government hospitals. The association between the literacy status of mothers and awareness regarding JE is found to be statistically significant. Furthermore, it was found that the association between vaccination coverage and area of residence of the beneficiaries in relation to session sites is statistically significant. Conclusion and Recommendation: The association of maternal literacy status with JE vaccination coverage was not significant, whereas the association with the awareness regarding JE was statistically significant. Four key messages of immunization should be delivered to every mother during vaccination.

Long-term immunogenicity of the SA14-14-2 Japanese encephalitis (JE) vaccine (CD.JEVAX®) booster following chimeric JE (IMOJEV®) vaccine priming in Thai children

ABSTRACT Japanese encephalitis (JE) is a significant public health concern in Asia, particularly in children, where vaccination plays a crucial role in prevention. In this study, we investigated the immunogenicity and safety of two different live-attenuated JE vaccines used as primary and booster doses. Fifty healthy participants aged 1–3 years, who were primed with the chimeric JE vaccine IMOJEV® a year earlier, received a booster dose of the SA14-14-2 JE vaccine CD.JEVAX®. To evaluate the immune response, JE-neutralizing antibody titers were assessed on day 0 (pre-booster), day 30, and annually from 1 to 5 years post-booster using the 50% plaque reduction neutralization test (JEPRNT50). The assessment revealed strong immunogenicity 30 d post-booster, with a geometric mean titer of 2092.4 [95% confidence interval (CI): 1473.9–2970.5] and a seroprotection rate of 100%, which gradually decreased to 97.5% at 5 years post-booster. No severe adverse events were observed. The most common reaction within 7 d of vaccination was fever (20%; 95% CI: 10.7–32.3). These results indicate that a booster dose of CD.JEVAX® elicits a strong immune response in children previously vaccinated with IMOJEV® while maintaining a good safety profile, thus supporting the interchangeability of these two live-attenuated JE vaccines. Registered at www.thaiclinicaltrials.org (TCTR ID: TCTR20221102003), our study suggests that CD.JEVAX® can be a viable option for booster vaccination in JE prevention programs, potentially enhancing vaccine flexibility and accessibility.

Coverage of Japanese Encephalitis Vaccine in Kalaburagi City, Karnataka, India: A Cross-Sectional Study after the Vaccination Campaign

Coverage of Japanese Encephalitis Vaccine in Kalaburagi City, Karnataka, India: A Cross-Sectional Study after the Vaccination Campaign

Impact of vaccination against Japanese encephalitis in endemic countries.

Japanese encephalitis (JE) virus is the leading cause of vaccine-preventable encephalitis and a significant cause of disability in Asia and the western Pacific. Many countries have introduced JE vaccination programs, including several low resource countries following WHO's prioritization of JE vaccination in 2006. We sought to characterize the public health impact of JE vaccination programs. JE case data and vaccination coverage rates, were requested from country health officials in 23 JE endemic countries and Chinese Taipei. Additional data were extracted from meeting presentations and published literature. JE incidence was compared before and after vaccination using a minimum three year period pre and post program introduction or expansion. Data suitable for analysis were available for 13 JE-endemic countries and Chinese Taipei, for either all age groups or for children aged under 15 years only. Five countries and Chinese Taipei introduced vaccine prior to 2006 and the all-age JE incidence was reduced by 73-100% in about 5-20 years following introduction. Six countries have introduced JE vaccine since 2006, and JE incidence in children aged younger than 15 years has been reduced by 14-79% as of 2015-2021. JE-specific data were unavailable before introduction in Thailand and Vietnam, but vaccination programs reduced acute encephalitis incidence by 80% and 74%, respectively. Even in the programs with greatest impact, it took several years to achieve their results. JE vaccination has greatly reduced JE in 13 JE-endemic countries and Chinese Taipei. Highest impact has been observed in countries that introduced prior to 2006, but it often took roughly two decades and substantial resources to achieve that level of success. For greatest possible impact, more recently introducing countries and funding agencies should commit to continuous improvements in delivery systems to sustain coverage after initial vaccine introduction.

Informing an investment case for Japanese encephalitis vaccine introduction in Bangladesh.

Japanese encephalitis virus (JEV) is a major threat to human health. Bangladesh is considering introducing a JEV vaccine; however, the investment case is hampered by a limited understanding of key aspects of JEV ecology. We conducted a seroprevalence study in a high-incidence region using an assay that limits cross-reactivity with dengue virus. We also trapped mosquitoes and collected information about potential host species. We used mathematical models to recover risk factors for infection and underlying probabilities of severe disease and death. We observed 19.0% [95% confidence interval (CI):17.1 to 21.1] of JEV antibodies. On average, 0.7% (95% CI: 0.2 to 2.0) of the susceptible population gets infected yearly, with pig proximity being the main human infection risk factor. Our traps captured 10 different mosquito species that have been linked with JEV transmission. We estimated that 1 in 1000 infections results in severe disease, 1 in 10,000 results in death, and 76% of severe cases are missed by surveillance.

Generation of soluble, immunoreactive recombinant JEV E protein through a simplified inclusion body extraction and refolding approach in vitro

Japanese encephalitis (JE) is a mosquito-borne infectious disease caused by the Japanese encephalitis virus (JEV). There is currently no effective treatment for JE, and all approved Japanese encephalitis vaccine products originated from the JEV genotype III (GIII). In recent years, JEV genotype I (GI) has gradually replaced GIII as the dominant genotype, and a new symptom of peripheral nerve injury (PNI) caused by JEV NX1889 strain has attracted wide attention, in which JEV envelope (E) protein may be involved in early peripheral nerve injury. Here, the envelope (E) gene of JEV GIb, NX1889 strain was cloned into pET-32a (+) plasmid, and then the E protein was successfully expressed as the high-yield inclusion body form in Escherichia coli (E. coli) BL21 (DE3). Subsequently, we successfully developed a simplified approach to generate soluble JEV E protein by solubilization, and a stepwise dialysis refolding approach with the introduction of a redox system. The refolding recombinant E protein was identified by anti-JEV-E polyclonal antibody and the serum anti-E titer of mice immunized with refolded E protein was higher than 1: 409,600, which proves it has highly immunoreactive. Moreover, the recombinant E protein could recognize antibodies in samples of multiple species and types, such as mice, rabbits, and humans. The approach described above is economical and does not require complex eukaryotic expression systems to produce immunoreactive JEV E protein, which may be of great significance for the diagnosis and pathogenesis of JEV GI strain.

Efficacy and Safety of a Tetravalent Dengue Vaccine (TAK-003) in Children With Prior Japanese Encephalitis or Yellow Fever Vaccination.

We explored the impact of prior Yellow fever (YF) or Japanese encephalitis (JE) vaccination on the efficacy of Takeda's dengue vaccine candidate, TAK-003 (NCT02747927). Children 4-16 years of age were randomized 2:1 to receive TAK-003 or placebo and were under active febrile surveillance. Symptomatic dengue was confirmed by serotype-specific RT-PCR. YF and JE vaccination history was recorded. Of the 20,071 children who received TAK-003 or placebo, 21.1% had a YF and 23.9% had a JE vaccination history at randomization. Fifty-seven months after vaccination, vaccine efficacy was 55.7% (95% CI, 39.7%-67.5%) in those with YF vaccination, 77.8% (70.8%-83.1%) for JE vaccination, and 53.5% (45.4%-60.4%) for no prior YF/JE vaccination. Regional differences in serotype distribution confound these results. The apparent higher vaccine efficacy in the JE vaccination subgroup could be largely explained by serotype-specific efficacy of TAK-003. Within 28 days of any vaccination, the proportions of participants with serious adverse events in the YF/JE prior vaccination population were comparable between the TAK-003 and placebo groups. The available data do not suggest a clinically relevant impact of prior JE or YF vaccination on TAK-003 performance. Overall, TAK-003 was well-tolerated and efficacious in different epidemiological settings.

Awareness About Child Immunization among Women in Rural Area of District Jalaun

Introduction; Universal Immunization Programme (UIP) is one of the largest public health programmes targeting close of 2.67 crore newborns and 2.9 crore pregnant women annually. It is one of the most cost-effective public health interventions and largely responsible for reduction of vaccine preventable under-5 mortality rate. Under UIP, immunization is providing free of cost against 12 vaccine preventable diseases. Mission Indra dhanush (MI) was launched in December 2014 and aims at increasing the full immunization coverage to children to 90 % (1). Mother play a very important role in child immunization, so awareness and correct knowledge about immunization is very essential in women, keeping this thing in mind, the present study was undertaken. Aims and objectives;1. To assess the awareness about child immunization among women in rural area.2. To know the correct knowledge of vaccine given in children among women .Material and methods;A cross sectional study was carried out in a rural area of district Jalaun. Aata block was selected randomly for study area. RHTC Aata was selected and women attending the OPD during month of August to October were included in study. Sample size were calculated and 140 mothers were interviewed by using predesigned and pretested questionnaire after taking verbal consent and data was collected and analyzed using appropriate statistical tool. Results; mostly women had heard about immunization in children (82.1%) and most of the women got information from health workers like ASHA/ANM followed by family and friends. vaccine given to child that shows knowledge about BCG/POLIO/MMR was found good but average about DPT and HEPATITIS. Very few women had knowledge about HIB, JE and ROTA vaccine. Conclusion; need to focus on education and awareness programme on women regarding child immunization in rural areas.

A Mathematical modelling for co-infection dynamics of Japanese encephalitis-Dengue and influence of JE Vaccine on Dengue disease

A non-linear deterministic mathematical model has been described with the co-infection dynamics of Japanese encephalitis(JE) and dengue disease, incorporating the JE vaccine. A basic reproduction number is discussed to study transmission potential of the co-infection model. In co-infection model, disease-free equilibrium points of Japanese encephalitis and dengue, along with endemic, are presented in system and investigated their stability with the help of their specified method. Our analysis suggests that vaccination against Japanese encephalitis positively affect control of co-infection. By using Center Manifold Theory, the model undergoes backwards bifurcation phenomenon and this has been occurred when basic reproduction number is smaller than unity. It is shown that by taking simultaneous preventive steps, the basic reproduction number of co-infection can be reduced to less than one after eliminating both infections. Sensitivity analysis has been performed to determine which parameters significantly affect disease dynamics. The effects of these parameters on transmission of disease were investigated using a numerical simulation. According to the findings, we obtain that JE-dengue co-infection can be managed with use of JE vaccine, also minimize JE transmission rate rapidly.

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.

Hesitancy towards Japanese Encephalitis vaccine and its socio-demographic correlates among parents attending to children aged

Problem consideredJapanese encephalitis (JE) is a mosquito-borne disease with a vaccine as the main preventive strategy. Vaccine hesitancy among parents can pose a threat to the success of child vaccination programmes. ObjectivesTo determine the level of awareness regarding the transmission, treatment and sequelae of JE, assess the levels and determining factors of vaccine hesitancy and acceptance among parents accompanying their children aged <15 years to the study hospitals. MethodsThis hospital-based cross-sectional study was conducted among 204 parents of children aged <15 years from February to May 2023. Data were collected using a pretested validated proforma and analysed using Jamovi software 2.3. Chi-square test and Binary Logistic Regression analyses were used. ResultsAmong, the 204 study participants (mean age 29.6 (±3.65) years), 73% (n = 129) were aged </ = 30 years, 71.1% (n = 145) were aware of the presence of JE in the study area. Awareness about transmission and consequences was less than 30%. Overall vaccine hesitancy was 84.3% (n = 172); it was higher among those >30 years (85.3% versus 83.7% among </ = 30 years, with >2 children (90% versus 84.0% among those having </ = 2 children). With overall 72.5% vaccine acceptance, participants aged ≤30 years (OR = 2.08 (95% CI: 1.01–4.34; p = 0.047) and those aware of JE cases in the area (OR 27.76 (95% CI, 12.67–65.53), p < 0001), had higher vaccine acceptance rate. ConclusionThe participants had high level of awareness about JE cases being reported; lack of knowledge regarding the JE transmission, treatment, and consequences; high JE vaccine hesitancy and low acceptance rate.

Mass immunisation to eradicate Japanese encephalitis: Real-world evidence from Guizhou Province in 2005–2021

ObjectivesTo explore epidemiological changes of Japanese encephalitis (JE) in a long-time span and evaluate the impact of mass immunisation. MethodData on JE cases from hospitals and the county Centers for Disease Control and Prevention in Guizhou Province was collected between 2005 and 2021. Epidemiological changes were analyzed according to a series of policy implementations and the coronavirus disease 2019 (COVID-19) pandemic. ResultsA total of 5138 JE cases and 152 deaths were reported in Guizhou Province during 2005–2021. The average incidence and case fatality rates were 0.83/100,000 and 2.96%, respectively. The JE prevalence showed a declining trend over the years with the reduced incidence gap between age groups and narrowing of the high-epidemic regions. During the COVID-19 pandemic, the JE activity reached its nadir in 2020. The inclusion in the Expanded Program on Immunization of the JE vaccine and catch-up immunisations showed a significant impact on the JE declining incidence rate. ConclusionsThe implementation of JE immunisation programs has played a crucial role in controlling its spread. Continued efforts should be made to maintain high coverage of the JE vaccine and strengthen disease surveillance systems, ensuring JE effective control and eventual elimination.

A novel alternative for pyrogen detection based on a transgenic cell line

Pyrogen, often as a contaminant, is a key indicator affecting the safety of almost all parenteral drugs (including biologicals, chemicals, traditional Chinese medicines and medical devices). It has become a goal to completely replace the in vivo rabbit pyrogen test by using the in vitro pyrogen test based on the promoted ‘reduction, replacement and refinement’ principle, which has been highly considered by regulatory agencies from different countries. We used NF-κB, a central signalling molecule mediating inflammatory responses, as a pyrogenic marker and the monocyte line THP-1 transfected with a luciferase reporter gene regulated by NF-κB as an in vitro model to detect pyrogens by measuring the intensity of a fluorescence signal. Here, we show that this test can quantitatively and sensitively detect endotoxin (lipopolysaccharide from different strains) and nonendotoxin (lipoteichoic acid, zymosan, peptidoglycan, lectin and glucan), has good stability in terms of NF-κB activity and cell phenotypes at 39 cell passages and can be applied to detect pyrogens in biologicals (group A & C meningococcal polysaccharide vaccine; basiliximab; rabies vaccine (Vero cells) for human use, freeze-dried; Japanese encephalitis vaccine (Vero cells), inactivated; insulin aspart injection; human albumin; recombinant human erythropoietin injection (CHO Cell)). The within-laboratory reproducibility of the test in three independent laboratories was 85%, 80% and 80% and the interlaboratory reproducibility among laboratories was 83.3%, 95.6% and 86.7%. The sensitivity (true positive rate) and specificity (true negative rate) of the test were 89.9% and 90.9%, respectively. In summary, the test provides a novel alternative for pyrogen detection.

COVID-19 and Japanese Encephalitis Vaccination: Occurrence of Disease in Area with and without Mandatory Vaccination Policies

COVID-19 and Japanese Encephalitis Vaccination: Occurrence of Disease in Area with and without Mandatory Vaccination Policies

Japanese Encephalitis: Risk of Emergence in the United States and the Resulting Impact.

Japanese encephalitis virus is a mosquito-borne member of the Flaviviridae family. JEV is the leading cause of viral encephalitis in Asia and is characterized by encephalitis, high lethality, and neurological sequelae in survivors. The virus also causes severe disease in swine, which are an amplifying host in the transmission cycle, and in horses. US agricultural authorities have recently recognized the threat to the swine industry and initiated preparedness activities. Other mosquito-borne viruses exotic to the Western Hemisphere have been introduced and established in recent years, including West Nile, Zika, and chikungunya viruses, and JEV has recently invaded continental Australia for the first time. These events amply illustrate the potential threat of JEV to US health security. Susceptible indigenous mosquito vectors, birds, feral and domestic pigs, and possibly bats, constitute the receptive ecological ingredients for the spread of JEV in the US. Fortunately, unlike the other virus invaders mentioned above, an inactivated whole virus JE vaccine (IXIARO®) has been approved by the US Food and Drug Administration for human use in advance of a public health emergency, but there is no veterinary vaccine. This paper describes the risks and potential consequences of the introduction of JEV into the US, the need to integrate planning for such an event in public health policy, and the requirement for additional countermeasures, including antiviral drugs and an improved single dose vaccine that elicits durable immunity in both humans and livestock.

Shift in dominant genotypes of Japanese encephalitis virus and its impact on current vaccination strategies.

Japanese encephalitis (JE) is a zoonotic ailment from the Japanese encephalitis virus (JEV). JEV belongs to the flavivirus genus and is categorized into a solitary serotype consisting of five genetically diverse genotypes (I, II, III, IV, and V). The JEV genotype III (GIII) was the prevailing strain responsible for multiple outbreaks in countries endemic to JEV until 1990. In recent years, significant improvements have occurred in the epidemiology of JE, encompassing the geographical expansion of the epidemic zone and the displacement of prevailing genotypes. The dominant genotype of the JEV has undergone a progressive shift from GIII to GI due to variations in its adaptability within avian populations. From 2021 to 2022, Australia encountered an epidemic of viral encephalitis resulting from infection with the GIV JEV pathogen. The current human viral encephalitis caused by GIV JEV is the initial outbreak since its initial discovery in Indonesia during the late 1970s. Furthermore, following a time frame of 50 years, the detection and isolation of GV JEV have been reported in Culex mosquitoes across China and South Korea. Evidence suggests that the prevalence of GIV and GV JEV epidemic regions may be on the rise, posing a significant threat to public safety and the sustainable growth of animal husbandry. The global approach to preventing and managing JE predominantly revolves around utilizing the GIII strain vaccine for vaccination purposes. Nevertheless, research has demonstrated that the antibodies generated by the GIII strain vaccine exhibit limited capacity to neutralize the GI and GV strains. Consequently, these antibodies cannot protect against JEV challenge caused by animal GI and GV strains. The limited cross-protective and neutralizing effects observed between various genotypes may be attributed to the low homology of the E protein with other genotypes. In addition, due to the GIV JEV outbreak in Australia, further experiments are needed to evaluate the protective efficiency of the current GIII based JE vaccine against GIV JEV. The alteration of the prevailing genotype of JEV and the subsequent enlargement of the geographical extent of the epidemic have presented novel obstacles in JE prevention and control. This paper examines the emerging features of the JE epidemic in recent years and the associated problems concerning prevention and control.

New Vaccine Introductions in WHO African Region between 2000 and 2022.

Significant progress has been made in vaccine development worldwide. This study examined the WHO African Region's vaccine introduction trends from 2000 to 2022, excluding COVID-19 vaccines. We extracted data on vaccine introductions from the WHO/UNICEF joint reporting form for 17 vaccines. We examined the frequency and percentages of vaccine introductions from 2000 to 2022, as well as between two specific time periods (2000-2010 and 2011-2022). We analysed Gavi eligible and ineligible countries separately and used a Chi-squared test to determine if vaccine introductions differed significantly. Three vaccines have been introduced in all 47 countries within the region: hepatitis B (HepB), Haemophilus influenzae type b (Hib), and inactivated polio vaccine (IPV). Between 2011 and 2022, HepB, Hib, IPV, the second dose of measles-containing vaccine (MCV2), and pneumococcal conjugate vaccine (PCV) were the five most frequently introduced vaccines. Hepatitis A vaccine has only been introduced in Mauritius, while Japanese encephalitis vaccine has not been introduced in any African country. Between 2000-2010 and 2011-2022, a statistically significant rise in the number of vaccine introductions was noted (p < 0.001) with a significant positive association between Gavi eligibility and vaccine introductions (p < 0.001). Significant progress has been made in the introduction of new vaccines between 2000 and 2022 in the WHO African Region, with notable introductions between 2011 and 2022. Commitments from countries, and establishing the infrastructure required for effective implementation, remain crucial.

The reemerging and outbreak of genotypes 4 and 5 of Japanese encephalitis virus.

The Japanese encephalitis virus (JEV) is classified into five distinct genotypes, with genotypes 1 and 3 historically showing higher activity. These genotypes are the primary agents of viral encephalitis in the Asian continent. Genotypes 4 and 5 have remained silent in low-latitude tropical regions since their discovery. From 2009, the hidden genotype 5 suddenly emerged simultaneously in mosquitoes from the Tibetan region of China and those from South Korea in East Asia. The detection of genotype 5 of JEV in these mosquitoes was associated with cases of viral encephalitis in the local population. Similarly, in 2022, the long-silent genotype 4 of JEV emerged in Australia, resulting in a local outbreak of viral encephalitis that primarily affected adults and caused fatalities. The emergence and outbreaks of genotypes 4 and 5 of JEV present new challenges for the prevention and control of Japanese encephalitis (JE). This study not only analyzes the recent emergence of these new genotypes but also discusses their implications in the development of JE vaccines and laboratory tests for newly emerging JEV infections.