Short-Term Immunogenicity and Safety of an Accelerated Pre-Exposure Prophylaxis Regimen With Japanese Encephalitis Vaccine in Combination With a Rabies Vaccine: A Phase III, Multicenter, Observer-Blind Study

Immunogenicity and safety of Vero cell culture-derived Japanese encephalitis vaccine: a phase 3 study in Chinese infants

BACKGROUND

Japanese encephalitis (JE) is a severe infectious disease of the central nervous system. Vaccination with Vero cell culture-derived vaccines may effectively reduce JE incidence.

RESEARCH DESIGN AND METHODS

In this single-center, randomized, blinded, positive-controlled clinical trial in China involving 600 healthy infants aged 6-11 months, participants were divided into experimental and control groups administered JEV-PI and JEV-LI, respectively. Antibody titers were determined after 0- and 7-day immunization schedules. A booster dose followed 12 months later.

RESULTS

After primary vaccination and before booster vaccination, the positive conversion rate, geometric mean titer (GMT), and geometric mean increase (GMI) of JEV-PI-neutralizing antibodies exceeded those of JEV-LI. After booster immunization, the GMT and GMI of JEV-PI were higher than those of JEV-LI. After primary immunization, the local, systemic, and overall adverse reactions were of grades 1 and 2, with a low incidence of grade 3. After booster immunization, these differences were mainly grades 1 and 2, with no differences between JEV-PI and JEV-LI.

CONCLUSION

JEV-PI is a promising vaccine as infants acquired long-lasting and highly neutralizing immune antibodies after inoculation with JEV-PI.

TRIAL REGISTRATION

The trial was registered in the Chinese Clinical Trial Registry (https://www.chictr.org.cn/showproj.html?proj = 203130; registration number: ChiCTR2300074692; registration date: 14/08/2023).

Immune response at 12-23 months following a single dose of Vero cell culture-derived Japanese encephalitis (JE) vaccine in adults previously vaccinated with mouse brain-derived JE vaccine

BACKGROUND

Japanese encephalitis (JE) virus is an important cause of neurological disease in Asia. JE vaccine is recommended for travelers with higher JE risk itineraries. Inactivated Vero cell culture-derived JE vaccine (JE-VC) is the only JE vaccine currently available in the United States. An inactivated mouse brain-derived JE vaccine (JE-MB) previously was available but production was discontinued. One JE-VC dose administered to adults previously vaccinated with ≥3 doses of JE-MB provides good short-term protection for at least one month, but data on longer-term protection are limited. We evaluated non-inferiority of the JE virus neutralizing antibody response at 12-23 months in JE-MB-vaccinated adults administered one JE-VC dose compared with JE vaccine-naïve adults administered a JE-VC two-dose primary series.

METHODS

We obtained archived sera from U.S. military personnel and performed a 50% plaque reduction neutralization test for anti-JE virus neutralizing antibodies. We compared the geometric mean titer (GMT) and seroprotection rate at 12-23 months after one JE-VC dose in previously JE-MB-vaccinated personnel and after the second JE-VC dose in previously JE vaccine-naïve personnel. Non-inferiority was concluded if the lower bound of the two-sided 95% confidence interval (CI) of the GMT ratio in previously vaccinated to vaccine-naïve personnel was >1/1.5.

RESULTS

The GMT in previously JE-MB-vaccinated persons was 75 (95% CI 63-90) and in previously JE vaccine-naïve persons was 12 (95% CI 11-14), and seroprotection rates were 94% (235/250) and 54% (135/250), respectively. The ratio of GMTs was 6.3 (95% CI: 5.0-7.7), satisfying the criterion for non-inferiority.

CONCLUSIONS

One JE-VC dose in previously JE-MB-vaccinated military personnel provides good protection for at least 1-2 years. The benefits of administration of a single JE-VC dose in previously JE-MB-vaccinated adults include a shorter time to completion of re-vaccination before travel, a decrease in the risk of adverse events, and reduced costs.

Vaccination against Japanese encephalitis with IC51: systematic review on immunogenicity, duration of protection and safety

Japanese encephalitis is a disease caused by a flavivirus which is transmitted by mosquitos in endemic countries. Considering the potentially severe outcomes of the disease, vaccination is recommended for those at risk of exposure. During recent years, IC51 (IXIARO®, JESPECT®, JEVAL®) has increasingly been used to protect travellers from Europe and the USA. However, no systematic review exists that summarizes the currently available evidence on the immunogenicity and safety of this vaccine. We conducted a systematic review on the immunogenicity and safety of IC51, using the databases PubMed, MEDLINE, EMBASE and ClinicalTrials.gov (search date: 31 August 2019). Data extracted from included studies were grouped by outcomes and stratified by population and setting. Risk of bias (ROB) was assessed using the RoB 2 tool for randomized controlled trials (RCTs) and ROBINS-I for non-randomized studies. Due to high heterogeneity, meta-analysis was not performed. A total of 32 studies from 16 countries met the inclusion criteria (15 RCTs, 17 non-randomized studies). ROB was serious or high in the majority of studies. Seroprotection rates ranged from 93 to 100% in adults (seven studies) and from 91 to 100% in children (four studies). In the study involving adults aged 64 years and older, seroprotection was 65% with higher rates in persons who were previously vaccinated against tick-borne encephalitis virus. Safety was investigated in 27 studies. Rates of serious adverse events were below 5% in all age groups, with the majority not being causally related to the vaccine. IC51 is a safe vaccine with good seroprotective abilities in persons aged >2 months to <64 years. The body of evidence, however, is weakened by a large amount of heterogeneity in study and clinical trial methodology. Further well-designed RCTs with special risk groups are needed.

Characteristics and preparation of the last-minute traveler: analysis of vaccine usage in the Global TravEpiNet Consortium

BACKGROUND

Last-minute travellers (LMTs) present challenges for health care providers because they may have insufficient time for recommended vaccinations or pre-travel preparation. Our objective was to obtain a better understanding of LMTs in order to help travel medicine providers develop improved strategies to decrease the number of LMTs and potentially reduce travel-related morbidity.

METHODS

We defined LMTs as travellers with a departure date of 7 days or fewer from the medical encounter. We analysed the characteristics and health preparation of 12 494 LMTs who presented to a network of US clinical practices for pre-travel health advice between January 2009 and December 2015.

RESULTS

LMTs comprised 16% of all travellers. More LMTs than non-LMTs travelled for business or to visit friends and relatives (VFR) (26% vs 16% and 15% vs 8%, respectively; P < 0.0001). More LMTs also travelled for longer than 1 month (27% vs 21%; P < 0.0001) and visited only urban areas (40% vs 29%; P < 0.0001). At least one travel vaccine was deferred by 18% of LMTs because of insufficient time before departure. Vaccines that required multiple vaccinations, such as Japanese encephalitis and rabies, were the most likely to be deferred because of time constraints.

CONCLUSION

Interventions to improve the timing of pre-travel health consultations should be developed, particularly for business and VFR travellers. Recently endorsed accelerated vaccine schedules for Japanese encephalitis and rabies may help some LMTs receive protection against these infections despite late presentation for pre-travel health care.

Japanese Encephalitis Vaccine: Recommendations of the Advisory Committee on Immunization Practices

This report updates the 2010 recommendations from the CDC Advisory Committee on Immunization Practices (ACIP) regarding prevention of Japanese encephalitis (JE) among U.S. travelers and laboratory workers (Fischer M, Lindsey N, Staples JE, Hills S. Japanese encephalitis vaccines: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recomm Rep 2010;59[No. RR-1]). The report summarizes the epidemiology of JE, describes the JE vaccine that is licensed and available in the United States, and provides recommendations for its use among travelers and laboratory workers.JE virus, a mosquitoborne flavivirus, is the most common vaccine-preventable cause of encephalitis in Asia. JE occurs throughout most of Asia and parts of the western Pacific. Approximately 20%-30% of patients die, and 30%-50% of survivors have neurologic, cognitive, or behavioral sequelae. No antiviral treatment is available.Inactivated Vero cell culture-derived JE vaccine (Ixiaro [JE-VC]) is the only JE vaccine that is licensed and available in the United States. In 2009, the U.S. Food and Drug Administration (FDA) licensed JE-VC for use in persons aged ≥17 years; in 2013, licensure was extended to include children aged ≥2 months.Most travelers to countries where the disease is endemic are at very low risk for JE. However, some travelers are at increased risk for infection on the basis of their travel plans. Factors that increase the risk for JE virus exposure include 1) traveling for a longer period; 2) travel during the JE virus transmission season; 3) spending time in rural areas; 4) participating in extensive outdoor activities; and 5) staying in accommodations without air conditioning, screens, or bed nets. All travelers to countries where JE is endemic should be advised to take precautions to avoid mosquito bites to reduce the risk for JE and other vectorborne diseases. For some persons who might be at increased risk for JE, the vaccine can further reduce the risk for infection. The decision about whether to vaccinate should be individualized and consider the 1) risks related to the specific travel itinerary, 2) likelihood of future travel to countries where JE is endemic, 3) high morbidity and mortality of JE, 4) availability of an effective vaccine, 5) possibility (but low probability) of serious adverse events after vaccination, and 6) the traveler's personal perception and tolerance of risk.JE vaccine is recommended for persons moving to a JE-endemic country to take up residence, longer-term (e.g., ≥1 month) travelers to JE-endemic areas, and frequent travelers to JE-endemic areas. JE vaccine also should be considered for shorter-term (e.g., <1 month) travelers with an increased risk for JE on the basis of planned travel duration, season, location, activities, and accommodations and for travelers to JE-endemic areas who are uncertain about their specific travel duration, destinations, or activities. JE vaccine is not recommended for travelers with very low-risk itineraries, such as shorter-term travel limited to urban areas or outside of a well-defined JE virus transmission season.

Molecular interaction of the antiviral compound CW‑33 and its analogues with the NS2B‑NS3 protease of the Japanese encephalitis virus

In a previous study from our group, a novel compound, namely CW‑33 (ethyl 2‑(3',5'‑dimethylanilino)‑​4‑oxo‑4,5‑dihydrofuran‑3‑carboxylate) was identified that exhibited antiviral activity for Japanese encephalitis virus (JEV). The viral NS2B‑NS3 serine protease serves an important role in cytoplasmic cleavage events that occur during viral polyprotein maturation. The inhibition of viral RNA and protein syntheses was responsible for the antiviral activities of the novel furanonaphthoquinone derivatives that were discovered for the prevention of JEV infection. Consequently, the present study examined the molecular docking simulation of JEV protease with compound CW‑33 and its analogues, and developed quantitative structure‑activity relationship (QSAR) models to assess the potential antiviral activities of these compounds with regard to JEV. Molecular docking simulation indicated the potential ligand‑protein interactions associated with the antiviral activities of these compounds. According to the results of the QSAR models, the secondary amine group was an important moiety required for compound bioactivity, which enabled the formation of hydrogen bonding with the residue Glu155. Furthermore, the aromatic ring mapping of the phenyl moiety of each compound was predicted to form a π‑cation interaction with residue Arg76, whereas the hydrophobic feature represented by the ethyl moiety exhibited hydrophobic contacts with residue Glu74. Finally, the hydrophobic substituents in the meta‑position of the phenyl ring further contributed to the efficacy of the antiviral activity. These results unravel the structural characteristics that are required for binding of CW‑33 to the JEV protease and can be used for potential therapeutic and drug development purposes for JEV.

Risk assessment for Japanese encephalitis vaccination

Japanese encephalitis (JE) is the most commonly diagnosed viral encephalitis in Asia. JE is caused by a virus called JE virus (JEV), a member of the genus Flavivirus, family Flaviviridae, and is transmitted by Culex mosquitoes. Neutralising antibody to JEV protects against JE, and can be induced by vaccination. JE is a potential threat to travellers to endemic areas, which are most of South and Southeast Asia and some Pacific Islands. The risk of JE can be expected to increase with increasing mosquito exposure and time spent in regions and seasons of active transmission. JE is very rare in travellers, but mortality is high, around 1 in 3, and there is a high rate of lasting neurological damage. JE can therefore be a profoundly life changing event for a traveller. Travellers and their healthcare providers need to balance the low risk of disease against the very high severity of disease if it does occur. In order to make an informed decision, the severity of JE disease should be carefully explained to travellers to Asia.

The changing epidemiology of Japanese encephalitis and New data: the implications for New recommendations for Japanese encephalitis vaccine

The epidemiology of Japanese Encephalitis and risk to the traveler has changed and continues to evolve. The spread of Japanese Encephalitis virus into new environments, changes in agricultural practice and animal vectors, climate change, peri-urban growth, changes in international travel to Asia, personal risk factors, mosquito vector free transmission, interactions with other flaviviruses and better information on infections without encephalitis and other factors make Japanese Encephalitis an underappreciated risk. There has also been a change in the incidence of Japanese Encephalitis cases that questions the current travel duration and geographic based recommendations. A safe, effective vaccine (Ixiaro) that may be administered in a short course regimen is now available in the United States without the risks of the previous vaccine. However, the vaccine is significantly underutilized. These changes in the epidemiology and new data on the risks of the Japanese Encephalitis virus require a review of the practice guidelines and expert recommendations that do not reflect the current state of knowledge.

An Update on Travel Vaccines and Issues in Travel and International Medicine

The fields of travel and international medicine are rapidly changing and growing. The role of occupational and travel health nurses is expanding and should be a focus for the future. At the American Association of Occupational Health Nurses Annual meeting on March 24, 2015, in Boston, five presentations were included in the session, An Update on Travel Vaccines and Issues in Travel and International Medicine. This article summarizes three of the presentations and includes a portion of the information generated by the Centers for Disease Control and Prevention (CDC) included in the fourth presentation. The first section focuses on the Essential Elements of Travel Medicine Programs including the pre-travel care assessment, trip research and risk identification, medication intervention review, non-pharmaceutical and prevention strategies, and post-travel care. The next section is an overview of key issues for business travelers. The growth in the number of international business travelers and unique aspects of business travel are emphasized in a comprehensive travel health program. This section also includes a discussion of expatriates and their special risks identified in recent literature (e.g., an assessment of the significant costs of health events and productivity losses by both business travelers and expatriates). The final section offers a specific example of a vaccine-preventable disease, namely, Japanese encephalitis (JE) virus, and needed changes in JE vaccine recommendations.

Travel vaccination recommendations and endemic infection risks in solid organ transplantation recipients

BACKGROUND

Solid organ transplant (SOT) recipients are often heavily immunosuppressed and consequently at risk of serious illness from vaccine preventable viral and bacterial infections or with endemic fungal and parasitic infections. We review the literature to provide guidance regarding the timing and appropriateness of vaccination and pathogen avoidance related to the immunological status of SOT recipients.

METHODS

A PUBMED search ([Vaccination OR vaccine] AND/OR ["specific vaccine"] AND/OR [immunology OR immune response OR cytokine OR T lymphocyte] AND transplant was performed. A review of the literature was performed in order to develop recommendations on vaccination for SOT recipients travelling to high-risk destinations.

RESULTS

Whilst immunological failure of vaccination in SOT is primarily the result of impaired B-cell responses, the role of T-cells in vaccine failure and success remains unknown. Vaccination should be initiated at least 4 weeks prior to SOT or more than 6 months post-SOT. Avoidance of live vaccination is generally recommended, although some live vaccines may be considered in the specific situations (e.g. yellow fever). The practicing physician requires a detailed understanding of region-specific endemic pathogen risks.

CONCLUSIONS

We provide a vaccination and endemic pathogen guide for physicians and travel clinics involved in the care of SOT recipients. In addition, recommendations based on timing of anticipated immunological recovery and available evidence regarding vaccine immunogenicity in SOT recipients are provided to help guide pre-travel consultations.

Immunizations

Vaccinations are a cornerstone of the pretravel consultation. The pretravel provider should assess a traveler's past medical history, planned itinerary, activities, mode of travel, and duration of stay and make appropriate vaccine recommendations. Given that domestic vaccine-preventable illnesses are more common in international travelers than are exotic or low-income nation-associated vaccine-preventable illnesses, clinicians should first ensure that travelers are current regarding routine immunizations. Additional immunizations may be indicated in some travelers. Familiarity with geographic distribution and seasonality of infectious diseases is essential. Clinicians should be cognizant of which vaccines are live, as there exist contraindications for live vaccines.

Japanese encephalitis: a review of clinical guidelines and vaccine availability in Asia

Travelers to Asia are at risk for acquiring Japanese Encephalitis (JEV), an arbovirus with high rates of morbidity and mortality. Recent advances in vaccination resulting in vaccines with low rates of side effects have strengthened the rationale to vaccinate more travelers to this region, as reflected in many updated national guidelines for prevention of disease in travelers. Vaccines however still require a complex pre-travel schedule and are costly, often leading to a requirement or desire for a vaccination option in the destination country. We explore current national guidelines for prevention of Japanese Encephalitis and seek to provide information on availability of JEV vaccines in various Asian countries.

Characteristics of Travelers to Asia Requiring Multidose Vaccine Schedules: Japanese Encephalitis and Rabies Prevention

BACKGROUND

Japanese encephalitis (JE) and rabies are serious vaccine preventable diseases which are an important consideration for travelers to Asia.

METHODS

Five Boston-area travel clinics collected demographic data, trip information, and interventions for travelers to Asia seen at pre-travel consultations from March 1, 2008, through July 31, 2010. We evaluated travelers for proportion vaccinated for JE and rabies, those traveling for >1 month, and whether travelers had adequate time to complete the JE series (clinic visit ≥28 days before departure) and rabies pre-exposure prophylaxis (clinic visit ≥21 days before departure).

RESULTS

Among 15,440 travelers from five Boston Area Travel Medicine Network travel clinics, Asia was the most common destination region, visited by 5,582 (36%) of travelers. Among these travelers, 4,810 (86%) planned to travel to only one Asian subregion. Median trip duration was 17 days, with more than 20% traveling for >1 month. The most common destinations were South (41%), Southeast (26%), and East (23%) Asia. Of those traveling to South, Southeast, or East Asia, over one-third with trips >1 month had insufficient time to complete a series for either JE or rabies vaccine. Overall, only 10% of travelers were vaccinated (past and pre-travel visit) for either JE or rabies, with lowest percentages among travelers visiting friends and relatives. Most travelers received advice on vector precautions (96%) and rabies prevention, which included avoiding animal contact, washing wounds, and obtaining appropriate post-exposure prophylaxis (88%).

CONCLUSION

Given the insufficient time for completion and relatively low vaccination rates, greater awareness of earlier pre-travel consultations, at least 4-6 weeks before travel, and accurate risk assessment for travelers are important. Effective counseling about vector avoidance, rabies, and animal bite prevention and management remains critical.

The Vero cell-derived, inactivated, SA14-14-2 strain-based vaccine (Ixiaro) for prevention of Japanese encephalitis

With an estimated 68,000 cases each year, Japanese encephalitis (JE) is the leading cause of viral encephalitis in Asia. Vaccination against the disease is recommended for endemic populations and also for travelers at risk. Recently, a Vero cell-derived, inactivated, SA14-14-2 strain-based JE vaccine (JE-VC) became available for travelers from non-endemic regions, replacing the traditional mouse brain-derived vaccines. First licensed in 2009, JE-VC is currently available in Europe, the USA, Canada, Australia and several other countries. In 2013, the vaccine was approved by the European Medicines Agency and the US Food and Drug Administration for use in children. This review summarizes current data on the immunogenicity, safety and clinical use of JE-VC.