Immunogenicity and safety of IXIARO (IC51) in a Phase II study in healthy Indian children between 1 and 3 years of age

Persistence of antibodies, boostability, and interchangeability of Japanese encephalitis vaccines: A systematic review and dose-response meta-analysis

BACKGROUND

The burden of Japanese encephalitis (JE) is substantial and is arguably one of the most serious viral encephalitic diseases with high case fatality and no specific treatment. JE vaccines are the only available mean to prevent the disease; however, the long-term persistence of antibodies, boostability, and interchangeability between different vaccine classes are not well understood.

METHODS

To summarise the evidence, PubMed, Embase, and Cochrane CENTRAL were systematically searched from their inception to March 2021. Dose-response meta-analysis was utilised to synthesise the proportion of individuals who were seropositive over time after a primary vaccination course and a booster dose. Proportion meta-analysis was conducted to estimate the proportion of individuals who were seropositive as well as those who reported adverse events following a booster dose with a different vaccine class.

RESULTS

Of 1053 publications retrieved, 27 studies with 4,558 participants were included. Of these, 11 studies assessed persistence of antibodies, 14 studies boostability, and 8 vaccine class interchangeability. The pooled seropositivity, 1-year after primary vaccination was 83.4% (95 %CI 78.2-89.5%) and remained stable for up to 5 years (82.7%; 95 %CI 76.1-89.4%). Rapid anamnestic response was observed 10 days post-booster dose, the proportion of individuals who were seropositive reached 96.9% (95 %CI 95.9-97.8%) and remained > 95% for up to 6 years. Inactivated mouse brain-derived vaccines followed by a booster dose of a different vaccine class was effective (i.e. seropositive 99%) and well tolerated.

CONCLUSIONS

A booster dose after the primary vaccination is effective and further booster doses may be needed after 7 years. Inactivated mouse brain-derived vaccine followed by a booster with a newer vaccine class is effective and safe; although, there is a paucity of data related to newer classes of vaccines interchangeability.

Comparison of immunogenicity and safety of licensed Japanese encephalitis vaccines: A systematic review and network meta-analysis

INTRODUCTION

Annually more than 100,000 Japanese encephalitis (JE) cases and 25,000 deaths worldwide are caused by JE virus infection. More than 15 JE vaccines are currently in use worldwide. It is unknown whether any of the vaccines is superior to the others in terms of immunogenicity and safety.

METHODS

Four databases were systematically searched for randomised controlled trials that compared two or more types of JE vaccines. Vaccines were classified into four classes: inactivated mouse brain-derived (oldest class), inactivated Vero cell, live chimeric, and live attenuated. Network meta-analysis was used to generate mixed effect estimates against inactivated mouse brain-derived vaccines for seroconversion, and against placebo for adverse event (AE) and severe adverse event (SAE).

RESULTS

23 studies (38,496 participants) were included. All newer vaccine classes had better immunogenicity, the difference was statistically significant for inactivated Vero cell (OR = 2.98; 95 %CI: 1.02-8.65) and live chimeric (OR = 5.93; 95 %CI: 1.73-20.32) vaccines. Inactivated mouse-derived vaccines had the highest odds for AEs (OR = 2.27; 95 %CI: 1.59-3.23), the odds of AE of newer vaccines was not different to placebo. There was no difference in SAEs across vaccine classes.

CONCLUSIONS

All newer JE vaccines have comparable safety profiles, live chimeric and inactivated Vero cell vaccines are the most immunogenic among the newer vaccine classes.

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.

Pediatric Travelers and Immigrant Children

Children comprise a special group of international travelers. Immigrant and refugee children, along with children traveling to visit friends and relatives abroad or on leisure trips, require special attention by clinicians to prevent and treat travel-related conditions. [Pediatr Ann. 2019;48(9):e360-e369.].

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.

Adverse events following vaccination with an inactivated, Vero cell culture-derived Japanese encephalitis vaccine in the United States, 2012-2016

BACKGROUND

In March 2009, the U.S. Food and Drug Administration licensed an inactivated Vero cell culture-derived Japanese encephalitis vaccine (JE-VC [IXIARO®]) for use in persons aged ≥17 years. In 2013, licensure was extended to include children aged ≥2 months. A previous analysis reviewed adverse events reported to the U.S. Vaccine Adverse Event Reporting System (VAERS) from May 2009 through April 2012.

METHODS

We reviewed adverse events reported to VAERS following JE-VC administered from May 1, 2012 through April 30, 2016. Adverse event reporting rates were calculated using 802,229 doses distributed.

RESULTS

During the 4-year period, 119 adverse event reports were received for a reporting rate of 14.8 per 100,000 doses distributed. Nine (8%) adverse events were classified as serious for a reporting rate of 1.1 per 100,000 distributed. The most commonly reported event was hypersensitivity (n = 24; 20%) for a rate of 3.0 per 100,000 doses distributed; 1 anaphylaxis event was reported. Ten (8%) neurologic events were reported for a rate of 1.2 per 100,000 doses distributed; 2 events were classified as seizures. Sixty-three (53%) adverse events occurred after a first dose of JE-VC. Eighty (67%) adverse events occurred after administration of JE-VC with other vaccines. Eleven (9%) adverse events were reported in children; 1 was considered serious.

CONCLUSIONS

These data continue to support the generally favorable safety profile of JE-VC. Reporting rates of adverse events were similar to those of the previous analysis. Although reporting rates of adverse events in children could not be calculated, there were low numbers of reported events in this age group. Post-licensure adverse event surveillance for this relatively new vaccine continues to be important to monitor adverse event reporting rates and identify possible rare serious events.

Overview of Japanese encephalitis disease and its prevention. Focus on IC51 vaccine (IXIARO®)

Japanese encephalitis (JE) is a vector-borne disease caused by the Japanese encephalitis virus (JEV). JEV is transmitted by mosquitoes to a wide range of vertebrate hosts, including birds and mammals. Domestic animals, especially pigs, are generally implicated as reservoirs of the virus, while humans are not part of the natural transmission cycle and cannot pass the virus to other hosts. Although JEV infection is very common in endemic areas (many countries in Asia), less than 1% of people affected develop clinical disease, and severe disease affects about 1 case per 250 JEV infections. Although rare, severe disease can be devastating; among the 30,000-50,000 global cases per year, approximately 20-30% of patients die and 30-50% of survivors develop significant neurological sequelae. JE is a significant public health problem for residents in endemic areas and may constitute a substantial risk for travelers to these areas. The epidemiology of JE and its risk to travelers have changed, and continue to evolve. The rapid economic growth of Asian countries has led to a surge in both inbound and outbound travel, making Asia the second most-visited region in the world after Europe, with 279 million international travelers in 2015. The top destination is China, followed by Thailand, Hong Kong, Malaysia and Japan, and the number of travelers is forecast to reach 535 million by 2030 (+ 4.9% per year). Because of the lack of treatment and the infeasibility of eliminating the vector, vaccination is recognized as the most efficacious means of preventing JE. The IC51 vaccine (IXIARO^®) is a purified, inactivated, whole virus vaccine against JE. It is safe, well tolerated, efficacious and can be administered to children, adults and the elderly. The vaccination schedule involves administering 2 doses four weeks apart. For adults, a rapid schedule (0-7 days) is available, which could greatly enhance the feasibility of its use. Healthcare workers should inform both short- and long-term travelers of the risk of JE in each period of the year and recommend vaccination. Indeed, it has been shown that short-term travelers are also at risk, not only in rural environments, but also in cities and coastal towns, especially in tourist localities where excursions to country areas are organized.

Safety and immunogenicity of an inactivated Vero cell_derived Japanese encephalitis vaccine (IXIARO®, JESPECT®) in a pediatric population in JE non-endemic countries: An uncontrolled, open-label phase 3 study

BACKGROUND

Young travelers to South-East Asia may be at risk for Japanese encephalitis (JE).

METHODS

IXIARO^® (0.25 ml or 0.5 ml, depending on age) were administrated to 100 travelers aged ≥ 2 months to < 18 years. Solicited AEs were collected for 7 days after each injection, unsolicited adverse events (AEs) for a total of 7 months. JE neutralizing antibodies were assessed in 64 subjects.

RESULTS

The most common solicited local AEs were redness (3/12 subjects), induration and tenderness (both 1/12) with 0.25 ml IXIARO^®, and tenderness (44/88) and pain (22/88) with 0.5 ml IXIARO^®. Common solicited systemic AEs were diarrhea (2/12) and loss of appetite (1/12) with 0.25 ml IXIARO^® and muscle pain (27/88) and excessive fatigue (10/88) with 0.5 ml IXIARO^®. In total, up to day 56, AEs were reported by 10/12 (83.3%) of subjects who received the 0.25 ml dose and 67/88 (76.1%) of those vaccinated with the 0.5 ml dose. All subjects (62/62; 100%) developed protective levels of JE neutralizing antibodies by Day 56 and 31/34 (91.2%) retained protective titers at Month 7.

CONCLUSIONS

IXIARO^® was generally well tolerated in children, with an overall AE profile similar to adults. IXIARO^® was highly immunogenic in both dose groups.

Immunogenicity and safety of inactivated chromatographically purified Vero cell-derived Japanese encephalitis vaccine in Thai children

Summary: Inactivated mouse-brain-derived Japanese encephalitis vaccine has a worrisome safety profile and the live attenuated vaccine is unsuitable in immunodeficiency. This study aimed to evaluate the immunogenicity and safety of an inactivated chromatographically purified Vero-cell-derived JE vaccine (CVI-JE, Beijing P-3 strain) in children.

152 healthy Thai children, with an average (SD) age of 14.4 (3.8) months, received 3 doses of CVI-JE on days 0, 7–28, and one year. Homologous JE neutralizing antibody titers (NT) were measured. All subjects had seroprotection [geometric mean titer (GMT) 150] 28 days' post 2nd vaccination. The seroprotection rates at 1 year after primary series and and 1 month after the booster were 89.3% (GMT 49) and 100% (GMT 621), respectively. Local and systemic reactions–fever (17.6%), vomiting (8%), and poor appetite (5.3%)–were noted within 28 days' post-vaccination. All these symptoms were self-limited.

Conclusions: CVI-JE is safe, immunogenic, and provided high NT.

Safety of the Inactivated Japanese Encephalitis Virus Vaccine IXIARO in Children: An Open-label, Randomized, Active-controlled, Phase 3 Study

BACKGROUND

Japanese encephalitis remains a serious health concern in Asian countries and has sporadically affected pediatric travelers. In the present study, we monitored the safety profile of the Japanese encephalitis virus vaccine IXIARO (Valneva Austria GmbH, Vienna, Austria) in a pediatric population.

METHODS

We randomized 1869 children between 2 months and 17 years of age in an age-stratified manner to vaccination with IXIARO or one of the control vaccines, Prevnar (formerly Wyeth Pharmaceuticals Inc., now Pfizer Inc., Kent, United Kingdom) and HAVRIX 720 (GlaxoSmithKline Biologicals, Rixensart, Belgium). Adverse events (AEs) (unsolicited and solicited local and systemic AEs), serious AEs and medically attended AEs were assessed up to day 56 and month 7 after the first dose.

RESULTS

Incidences of AEs, serious AEs or medically attended AEs did not differ significantly between the groups in any age stratum. AEs were most frequent in children <1 year of age and decreased with age. AEs of special interest, predefined as AEs associated with potential hypersensitivity/allergy or neurologic disorders up to day 56, were reported in 4.6% (IXIARO) versus 6.3% (Prevnar) in the ≥2 months to <1 year age group and 3.4% (IXIARO) versus 3.3% (HAVRIX) in the ≥1 to <18 years age group. Fever, the most frequent systemic reaction in 23.7% of infants to 3.8% of adolescents, decreased with age and did not differ between groups.

CONCLUSIONS

The safety profile of IXIARO was comparable to the control vaccines in terms of overall AE rates, serious AEs and medically attended AEs.

Immunogenicity of the Inactivated Japanese Encephalitis Virus Vaccine IXIARO in Children From a Japanese Encephalitis Virus-endemic Region

BACKGROUND

Japanese encephalitis (JE) is a major public health concern in Asia and poses a small but potentially fatal threat to travelers from nonendemic countries, including children. No JE vaccine for pediatric use has been available in Europe and the United States.

METHODS

Age-stratified cohorts of children between 2 months and 17 years received 2 doses of Vero cell-derived inactivated JE virus vaccine (IXIARO; Valneva Austria GmbH, Vienna, Austria) administered 28 days apart [<3 years, 0.25 mL (half adult dose); ≥3 years, 0.5 mL (full adult dose)]. Immunogenicity endpoints were seroconversion rate, 4-fold increase in JE neutralizing antibody titer and geometric mean titer assessed 56 days and 7 months after the first vaccination in 496 subjects of the intent-to-treat population. The immune response to JE virus at both time points was also analyzed according to prevaccination JE virus and dengue virus serostatus.

RESULTS

At day 56, seroconversion was attained in ≥99.2% of subjects with age-appropriate dosing, 4-fold increases in titer were reported for 77.4%-100% in various age groups, and geometric mean titers ranged from 176 to 687, with younger children having the strongest immune response. At month 7, seroconversion was maintained in 85.5%-100% of subjects. Pre-existing JE virus immunity did not impact on immune response at day 56; however, it led to a better persistence of protective antibody titers at month 7.

CONCLUSIONS

IXIARO is highly immunogenic at both doses tested in the pediatric population, leading to protective antibody titers at day 56 in >99% of subjects who received the age-appropriate dose.

Japanese encephalitis vaccines: Immunogenicity, protective efficacy, effectiveness, and impact on the burden of disease

Japanese encephalitis (JE) is a serious public health concern in most of Asia. The disease is caused by JE virus (JEV), a flavivirus transmitted by Culex mosquitoes. Several vaccines have been developed to control JE in endemic areas as well as to protect travelers and military personnel who visit or are commissioned from non-endemic to endemic areas. The vaccines include inactivated vaccines produced in mouse brain or cell cultures, live attenuated vaccines, and a chimeric vaccine based on the live attenuated yellow fever virus 17D vaccine strain. All the marketed vaccines belong to the JEV genotype III, but have been shown to be efficacious against other genotypes and strains, with varying degrees of cross-neutralization, albeit at levels deemed to be protective. The protective responses have been shown to last three or more years, depending on the type of vaccine and the number of doses. This review presents a brief account of the different JE vaccines, their immunogenicity and protective ability, and the impact of JE vaccines in reducing the burden of disease in endemic countries.

Product review on the JE vaccine IXIARO

Japanese encephalitis virus, as the most important vaccine-preventable cause of viral encephalitis in Asia, is estimated to cause over 68,000 clinical cases yearly. In endemic areas, most Japanese encephalitis infections occur in children younger than 10 y and clinical manifestation of this disease is critical, because there is no effective treatment available. As JEV infections are regarded as one of the most serious viral causes of encephalitis and mass immunization programmes are generally recommended for residents in endemic areas, a safe and effective JEV vaccine was needed to protect them as well as others at risk. Due to the safety concerns with the mouse brain derived vaccine, second generation vaccines against JE produced in cell culture like Vero cells were developed. IXIARO® is a purified, inactivated aluminum-adjuvanted JE vaccine, based on the SA14-14-2 virus strain, and is available in North America, Europe, Canada, Switzerland, Singapore, Hong Kong and Israel as well as in Australia & New Zealand (as JESPECT®).The safety, tolerability and immunogenicity profile of IXIARO® is well established through a number of clinical studies comparing IXIARO® with placebo as well as mouse brain derived vaccine. Recent data show that the global incidence of JE remains substantial, especially young children in endemic areas are most susceptible. As vaccination is the most feasible, reliable and cost effective tool for JE control, IXIARO® with confirmed excellent safety profile is highly recommendable, in particular for vaccination of children at risk. The European Commission as well as the FDA approved the extension of indication of IXIARO® to the pediatric segment (2 months of age and older) based on these data.

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.

A Japanese Encephalitis Vaccine From India Induces Durable and Cross-protective Immunity Against Temporally and Spatially Wide-ranging Global Field Strains

BACKGROUND

Japanese encephalitis (JE) is a vaccine-preventable acute disease. We report the results of a phase 2/3 trial of JENVAC, a Vero cell-derived vaccine developed using an Indian strain of JE virus (JEV).

METHODS

JENVAC was administered in 2 doses 28 days apart, and immunogenicity was compared to that from a single dose of SA-14-14-2, the only approved JE vaccine and regimen at the time in India.

RESULTS

After both the doses, seroconversion and seroprotection were >90% for JENVAC. For SA-14-14-2, seroconversion and seroprotection were 57.69% and 77.56%, respectively, on day 28 and 39.74% and 60.26%, respectively, on day 56. The geometric mean titers at day 28 and day 56 were 145.04 and 460.53, respectively, for JENVAC and 38.56 and 25.29, respectively, for SA-14-14-2. With a single dose of JENVAC, seroprotection titers lasted at least 12 months in >80% of the subjects. Following receipt of 2 doses, 61.17% of subjects retained seroprotection titers at 24 months, and immunogenicity criteria were higher than that for SA-14-14-2 at 12, 18, and 24 months each. Sera from JENVAC subjects neutralized JEV genotypes I, II, III, and IV equally well. Adverse events were not significantly different between the 2 vaccines.

CONCLUSIONS

JENVAC elicits long-lasting, broadly protective immunity.

CLINICAL TRIALS REGISTRATION

CTRI/2011/07/001855.

Safety and immunogenicity of a freeze-dried, Vero cell culture-derived, inactivated Japanese encephalitis vaccine (KD-287, ENCEVAC®) versus a mouse brain-derived inactivated Japanese encephalitis vaccine in children: a phase III, multicenter, double-blinded, randomized trial

Background

Although mouse brain-derived, inactivated Japanese encephalitis vaccines (JE-MBs) have been successfully used for a long time, potential rare neurological complications have prompted the development of a Vero cell culture-derived inactivated vaccine (JE-VC). In a phase III clinical study, we aimed to compare the safety and immunogenicity of a JE-VC, KD-287 with a JE-MB, JEV-GCC, in children.

Methods

In this multicenter, double-blinded, randomized controlled trial, the study population consisted of 205 healthy Korean children aged 12–23 months. Each subject was subcutaneously vaccinated with either KD-287 or JEV-GCC twice at an interval of 2 weeks and then vaccinated once 12 months after the second vaccination. Neutralizing antibodies were measured by the plaque reduction neutralization test using the homologous and heterologous, as a post hoc analysis, challenge virus strains.

Results

The three-dose regimen of KD-287 showed a comparable safety profile with JEV-GCC except higher incidence of fever after the first dose (30.4% and 14.7%, respectively). Most of the fever was mild degree (61.3% and 66.7%, respectively). KD-287 fulfilled the non-inferiority criteria for seroconversion rate (SCR) and geometric mean titer (GMT) of the neutralizing antibody, which were the primary endpoints, at 4 weeks after the third vaccination (95% CI: −1.00, 3.10 for the SCR difference and 10.8, 17.6 for the GMT ratio). The SCRs of KD-287 were all 100% and the GMTs were higher in the KD-287 group than in the JEV-GCC group after the second vaccination and before and after the third vaccination (GMT ratio: 5.59, 20.13, and 13.79, respectively, p < 0.001 in all). GMTs were higher in the KD-287 group in the heterologous analysis also (GMT ratio: 4.05, 5.15, and 4.19, respectively, p < 0.001 in all).

Conclusions

This study suggests that the KD-287, a JE-VC is as safe as and may be more effective than the licensed MB-derived vaccine. KD-287 could thus be useful as a second-generation vaccine and substitute for the current JE-MB vaccine in Korean children.

Trial registration

ClinicalTrials.gov: NCT01150942

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-014-0744-4) contains supplementary material, which is available to authorized users.

Comparing the immunogenicity and safety of 3 Japanese encephalitis vaccines in Asia-Pacific area: A systematic review and meta-analysis

Japanese encephalitis virus (JEV), a leading cause of Japanese encephalitis (JE) in children and adults, is a major public health problem in Asian countries. This study reports a meta-analysis of the immunogenicity and safety of vaccines used to protect infants or children from JE. Three types of JE vaccine were examined, namely, Japanese encephalitis live-attenuated vaccine (JEV-L), Japanese encephalitis inactivated vaccine (Vero cell) (JEV-I(Vero)), and Japanese encephalitis inactivated vaccine (primary hamster kidney cell) (JEV-I(PHK)). These vaccines are used to induce fundamental immunity against JE; however, few studies have compared their immunogenicity and safety in infants and young children less than 2 years of age. Data were obtained by searching 5 databases: Web of Science, PubMed, China National Knowledge Infrastructure, the China Wanfang database, and the Cochrane database. Fifteen articles were identified and scored using the Jadad score for inclusion in the meta-analysis. Random effect models were used to calculate the pooled seroconversion rate and adverse reaction rate when tests for heterogeneity were significant. The results showed that the pooled seroconversion rate for JEV-I(PHK) (62.23%) was lower than that for JEV-I(Vero) (86.49%) and JEV-L (83.52%), and that the pooled adverse reaction rate for JEV-L (18.09%) was higher than that for JEV-I(PHK) (10.08%) and JEV-I(Vero) (12.49%). The pooled relative risk was then calculated to compare the seroconversion and adverse reaction rates. The results showed that JEV-I(Vero) and JEV-L were more suitable than JEV-I(PHK) for inducing fundamental immunity to JE in infants and children less than 2 years of age.

Indian Academy of Pediatrics (IAP) recommended immunization schedule for children aged 0 through 18 years, India, 2013 and updates on immunization

JUSTIFICATION

There is a need to review/revise recommendations about existing vaccines in light of recent developments in the field of vaccinology where new developments are taking place regularly at short intervals.

PROCESS

Following an IAP ACVIP meeting on 3rd and 4th August, 2013, a draft of revised recommendations for the year 2013 and updates on certain new vaccine formulations was prepared and circulated among the meeting participants to arrive at a consensus.

OBJECTIVES

To review and revise recommendations for 2013 Immunization timetable for pediatricians in office practice and issue statements on new vaccine formulations.

RECOMMENDATIONS

The major change in the 2013 Immunization timetable was made in the recommendations pertaining to pertussis immunization. Taking in to the consideration of recent outbreaks of pertussis in many industrialized countries using acellular pertussis (aP) vaccines and subsequent finding of faster waning of the same in comparison to whole-cell pertussis (wP) vaccines and superior priming with wP vaccines than aP vaccines, the committee has now recommended wP vaccines for the primary series of infant vaccination. Guidelines are now also issued on the preference/selection of a particular aP vaccine in case it is not feasible to use wP vaccine, and use of Tdap vaccine during pregnancy. The administration schedule of monovalent human rotavirus vaccine, RV1 has been revised to 10 and 14 weeks from existing 6 and 10 weeks. Recommendation is made for the need of booster dose of live attenuated SA-14-14-2 JE vaccine. Updates and recommendations are issued on new typhoid conjugate vaccine, inactivated vero-cell culture derived SA-14-14-2 JE vaccine, inactivated vero-cell derived Kolar strain, 821564XY JE vaccine, and new meningococcal conjugate vaccines. This year the recommended immunization schedule with range for persons aged 0 through 18 years is being published together instead of two separate schedules. A subcategory of general instruction is added in footnotes. The comments and footnotes for several vaccines are revised and separate instructions for routine vaccination and catch-up vaccination are added in the footnotes section wherever applicable.

IXIARO updated: overview of clinical trials and developments with the inactivated vaccine against Japanese encephalitis

The mosquito-borne Japanese encephalitis virus causes an estimated 50,000 cases in Asia, accounting for at least 10,000 deaths and 15,000 cases of neuropsychiatric sequelae. IXIARO (Intercell AG, Vienna, Austria), an inactivated, Vero cell-derived vaccine against Japanese encephalitis was introduced in 2009. The vaccine is highly immunogenic, showing significantly higher geometric mean antibody titers compared with previous, mouse brain-derived vaccines. Postmarketing studies have confirmed the excellent safety profile. Studies on children aged 2 months to 18 years have been published. Based on these data, positive opinion from the EMA for vaccination of children has recently been given. Since a safe and effective vaccine against Japanese encephalitis is now available, outdated guidelines and recommendations have to be revised: travelers to rural areas of Asia should generally be recommended vaccination.

Safety of Japanese encephalitis live attenuated vaccination in post-marketing surveillance in Guangdong, China, 2005-2012

We reviewed the adverse events following immunization of live attenuated Japanese encephalitis vaccine in Guangdong Province, China. During the period of 2005-2012, 23 million doses of live attenuated Japanese encephalitis vaccine were used and 1426 adverse events were reported (61.24 per million doses); of which, 570 (40%) were classified as allergic reactions (24.48 per million doses), 31 (2%) were neurologic events (1.33 per million doses), and 36 (2.5%) were diagnosed as serious adverse events (1.55 per million doses). This study suggests that the JEV-L has a reasonable safety profile, most adverse events are relatively mild, with relatively rare neurologic events being observed.

A review of successful flavivirus vaccines and the problems with those flaviviruses for which vaccines are not yet available

Genus flavivirus comprises many important human pathogens causing public health problems worldwide. Some flavivirus infections are characterized by a relatively high mortality rate and/or high sequelae rate in survivors. Because most flavivirus life cycles are maintained between arthropod vectors and amplifying/reservoir hosts in the absence of humans, eradication of flaviviruses might be extremely difficult. Flavivirus vaccine development is considered a reasonable method to prevent flavivirus infections. Some vaccines have been successfully developed, but others have not, regardless of much effort. This review article describes currently available flavivirus vaccines against yellow fever, Japanese encephalitis, and tick-borne encephalitis. In addition, the current status of dengue and West Nile virus vaccine development is reviewed and problems regarding their development are discussed.

Immunogenicity and safety of currently available Japanese encephalitis vaccines: a systematic review

A number of Japanese encephalitis (JE) vaccines have been used for preventing Japanese encephalitis around the world. We here reviewed the immunogenicity and safety of the currently available Japanese encephalitis vaccines. We searched Pubmed, Embase, Web of Science, the Cochrane Library and other online databases up to March 25, 2014 for studies focusing on currently used JE vaccines in any language. The primary outcomes were the seroconversion rate against JEV and adverse events. Meta-analysis was performed for the primary outcome when available. A total of 51 articles were included. Studies were grouped on the basic types of vaccines. This systematic review led to 2 aspects of the conclusions. On one hand, all the currently available JE vaccines are safe and effective. On the other hand, the overall of JE vaccine evaluation is disorganized, the large variation in study designs, vaccine types, schedules, doses, population and few hand-to-hand trails, make direct comparisons difficult. In order to make a more evidence-based decision on optimizing the JE vaccine, it is warranted to standardize the JE vaccine evaluation research.

Japanese B Encephalitis: An Overview of the Disease and Use of Chimerivax-JE as a Preventative Vaccine

The Japanese encephalitis virus (JEV) is endemic in many countries in southern Asia and the western Pacific Rim, with new spread to previously unrecognized countries. It is an important cause of childhood neurological disease associated with permanent neurological sequelae and death. Fortunately, JE is a vaccine-preventable disease. The ChimeriVax™-JE (Sanofi Pasteur, Lyon, France) is a live-attenuated chimeric vaccine derived from the live-attenuated yellow fever virus, YF17D, which expresses the envelope proteins of the attenuated JEV vaccine strain, SA14-14-2. It is a safe, well-tolerated vaccine that is highly immunogenic in adults and children. The average geometric mean neutralizing antibody titer (GMT) in adults is 1,392 and over 90% of adults remain seroprotected 5 years after vaccination. In children and toddlers, more than 80% remain seroprotected 2 years after primary vaccination and demonstrate a robust and durable anamnestic response (>500-fold rise in GMT) with 99.1% seroprotection rates 1 year after a booster vaccine dose. The ChimeriVax™-JE is effective in children living in endemic regions where the vaccine could possibly be integrated into existing childhood vaccination programs. ChimeriVax™-JE is also indicated for travelers at risk of JE infection.

Japanese encephalitis: the virus and vaccines

Japanese encephalitis (JE) is an infectious disease of the central nervous system caused by Japanese encephalitis virus (JEV), a zoonotic mosquito-borne flavivirus. JEV is prevalent in much of Asia and the Western Pacific, with over 4 billion people living at risk of infection. In the absence of antiviral intervention, vaccination is the only strategy to develop long-term sustainable protection against JEV infection. Over the past half-century, a mouse brain-derived inactivated vaccine has been used internationally for active immunization. To date, however, JEV is still a clinically important, emerging, and re-emerging human pathogen of global significance. In recent years, production of the mouse brain-derived vaccine has been discontinued, but 3 new cell culture-derived vaccines are available in various parts of the world. Here we review current aspects of JEV biology, summarize the 4 types of JEV vaccine, and discuss the potential of an infectious JEV cDNA technology for future vaccine development.

IXIARO® updated: overview of clinical trials and developments with the inactivated vaccine against Japanese encephalitis

The mosquito-borne Japanese encephalitis virus causes an estimated 50,000 cases in Asia, accounting for at least 10,000 deaths and 15,000 cases of neuropsychiatric sequelae. IXIARO® (Intercell AG, Vienna, Austria), an inactivated, Vero cell-derived vaccine against Japanese encephalitis was introduced in 2009. The vaccine is highly immunogenic, showing significantly higher geometric mean antibody titers compared with previous, mouse brain-derived vaccines. Postmarketing studies have confirmed the excellent safety profile. Studies on children aged 2 months to 18 years have been published. Based on these data, positive opinion from the EMA for vaccination of children has recently been given. Since a safe and effective vaccine against Japanese encephalitis is now available, outdated guidelines and recommendations have to be revised: travelers to rural areas of Asia should generally be recommended vaccination.

Memory immune response and safety of a booster dose of Japanese encephalitis chimeric virus vaccine (JE-CV) in JE-CV-primed children

Japanese encephalitis chimeric virus vaccine (JE-CV) is a licensed vaccine indicated in a single dose administration for primary immunization. This controlled phase III comparative trial enrolled children aged 36-42 mo in the Philippines. 345 children who had received one dose of JE-CV in a study two years earlier, received a JE-CV booster dose. 105 JE-vaccine-naïve children in general good health were randomized to receive JE-CV (JE-vaccine naïve group; 46 children) or varicella vaccine (safety control group; 59 children). JE neutralizing antibody titers were assessed using PRNT50. Immunological memory was observed in children who had received the primary dose of JE-CV before. Seven days after the JE-CV booster dose administration, 96.2% and 66.8% of children were seroprotected and had seroconverted, respectively, and the geometric mean titer (GMT) was 231 1/dil. Twenty-eight days after the JE-CV booster dose seroprotection and seroconversion were achieved in 100% and 95.3% of children, respectively, and the GMT was 2,242 1/dil. In contrast, only 15.4% of JE-CV-vaccine naïve children who had not received any prior JE vaccine were seroprotected seven days after they received JE-CV. One year after receiving the JE-CV booster dose, 99.4% of children remained seroprotected. We conclude that JE-CV is effective and safe, both as a single dose and when administrated as a booster dose. A booster dose increases the peak GMT above the peak level reached after primary immunization and the antibody persistence is maintained at least one year after the JE-CV booster dose administration. Five year follow up is ongoing.

Safety and immunogenicity of a freeze-dried, cell culture-derived Japanese encephalitis vaccine (Inactivated) (JEBIK(®)V) in children

Freeze dried, cell culture-derived Japanese encephalitis vaccine (Inactivated) (JEBIK(®)V) is approved for a three-dose primary immunization followed by a one-dose booster immunization in Japan. We conducted a multicenter, double-blinded, randomized controlled trial of the safety and immunogenicity of the vaccine in 370 healthy children who received three doses of 5, 2.5 or 1.25 μg of virus protein per 0.5 mL formulation subcutaneously. Children received two doses of test vaccine 7-28 days apart followed by a dose 6-12 months after the second vaccination. The three-dose regimen showed a good safety profile with no serious vaccine-related adverse events. Fever and reactions at the injection site were common adverse reactions at each dose of vaccine. The seroconversion rates were 100%, 99.2% and 95.0% after two doses in the 5, 2.5 and 1.25 μg groups, respectively, and 100.0% after three doses in all groups. The geometric mean titers were high for all three formulations after the second and third doses, with a very clear dose-response relationship. These results indicate that JEBIK(®)V is likely to be a useful vaccine.

Vaccination of travelers: how far have we come and where are we going?

Vaccine recommendations are a prominent part of health preparations before international travel. We review progress made in the past decade regarding vaccines used primarily by persons traveling from high-income countries to low- and middle-income countries. The combined hepatitis A-B vaccine, the recently licensed Vero cell-derived Japanese encephalitis vaccine and conjugated quadrivalent meningococcal vaccines are discussed. This article provides updates on yellow fever vaccine-associated visceral and neurologic adverse events, indications for influenza vaccine in travelers, the rapid immunization schedule for tick-borne encephalitis vaccine, schedules for postexposure rabies prophylaxis, and new insights about oral cholera vaccines following the outbreak in Haiti. The future should bring vaccines for serogroup B Neiserria meningitidis, dengue and malaria, as well as an inactivated yellow fever vaccine.

Japanese Encephalitis Vaccines

Japanese encephalitis (JE) is a significant human health concern in Asia, Indonesia and parts of Australia with more than 3 billion people potentially at risk of infection with Japanese encephalitis virus (JEV), the causative agent of JE. Given the risk to human health and the theoretical potential for JEV use as a bioweapon, the development of safe and effective vaccines to prevent JEV infection is vital for preserving human health. The development of vaccines for JE began in the 1940s with formalin-inactivated mouse brain-derived vaccines. These vaccines have been shown to induce a protective immune response and to be very effective. Mouse brain-derived vaccines were still in use until May 2011 when the last lots of the BIKEN(®) JE-VAX(®) expired. Development of modern JE vaccines utilizes cell culture-derived viruses and improvements in manufacturing processes as well as removal of potential allergens or toxins have significantly improved vaccine safety. China has developed a live-attenuated vaccine that has proven to induce protective immunity following a single inoculation. In addition, a chimeric vaccine virus incorporating the prM and E structural proteins derived from the live-attenuated JE vaccine into the live-attenuated yellow fever 17D vaccine virus backbone is currently in clinical trials. In this article, we provide a summary of JE vaccine development and on-going clinical trials. We also discuss the potential risk of JEV as a bioweapon with a focus on virus sustainability if used as a weapon.

IMOJEV(®): a Yellow fever virus-based novel Japanese encephalitis vaccine

Japanese encephalitis (JE) is a disease of the CNS caused by Japanese encephalitis virus (JEV). The disease appears in the form of frequent outbreaks in most south- and southeast Asian countries and the virus has become endemic in several areas. There is no licensed therapy available and disease control by vaccination is considered to be most effective. Mouse brain-derived inactivated JE vaccines, although immunogenic, have several limitations in terms of safety, availability and requirement for multiple doses. Owing to these drawbacks, the WHO called for the development of novel, safe and more efficacious JE vaccines. Several candidate vaccines have been developed and at least three of them that demonstrated strong immunogenicity after one or two doses of the vaccine in animal models were subsequently tested in various clinical trials. One of these vaccines, IMOJEV(®) (JE-CV and previously known as ChimeriVax™-JE), is a novel recombinant chimeric virus vaccine, developed using the Yellow fever virus (YFV) vaccine vector YFV17D, by replacing the cDNA encoding the envelope proteins of YFV with that of an attenuated JEV strain SA14-14-2. IMOJEV was found to be safe, highly immunogenic and capable of inducing long-lasting immunity in both preclinical and clinical trials. Moreover, a single dose of IMOJEV was sufficient to induce protective immunity, which was similar to that induced in adults by three doses of JE-VAX(®), a mouse brain-derived inactivated JE vaccine. Recently, Phase III trials evaluating the immunogenicity and safety of the chimeric virus vaccine have been successfully completed in some JE-endemic countries and the vaccine manufacturers have filed an application for vaccine registration. IMOJEV may thus be licensed for use in humans as an improved alternative to the currently licensed JE vaccines.

Long term immunity following a booster dose of the inactivated Japanese Encephalitis vaccine IXIARO®, IC51

INTRODUCTION

IXIARO (IC51), a recently approved inactivated Japanese Encephalitis vaccine, is immunogenic and safe in a 0/28 days primary immunization schedule. Neutralizing antibody titers decline with time and booster doses are likely needed to enhance persistence of immunity.

OBJECTIVES

To assess the effect of a booster dose on neutralizing JE antibody titers for up to 12 months after boostering.

METHODS

In this phase III trial, 198 subjects, who had received primary immunization in a preceding randomized trial, were boosted with IXIARO 15 months after the primary immunization. Neutralizing antibody titers were assessed by plaque-reduction neutralisation test, PRNT.

RESULTS

Prior to the booster dose, 69.2% (137/198) of subjects had PRNT50 titers ≥ 1:10. One month after the booster, the rate of subjects with PRNT50 ≥ 1:10 (recognized as a protective titer) was 100%. This rate remained high at 98.5% at 6 and 12 months; GMTs were 22.5 before the booster and 900, 487 and 361 at 1, 6 and 12 months after the booster, respectively.

CONCLUSION

A booster dose of IXIARO at 15 months after primary immunization was highly immunogenic with GMTs >5-fold higher than those seen immediately after primary immunization, and remained at high levels for at least 12 months after the booster.

Pediatric travelers visiting friends and relatives (VFR) abroad: illnesses, barriers and pre-travel recommendations

Global mobility has shown a steady rise in recent years, with increased immigration and international travel. The VFR traveler is a traveler whose primary purpose of travel is to visit friends and relatives (VFR), where there is a gradient of risk between home and destination. Children are more likely to be VFR travelers than adults. Pediatric VFR travelers have higher risks for certain infectious travel-related illnesses and face multiple barriers in receiving comprehensive pre-travel care. This review focuses on the current state of knowledge of the pediatric VFR traveler, including epidemiological risks, barriers to adequate pre-travel services, and specific recommendations for disease prevention.

Combating Japanese encephalitis: Vero-cell derived inactivated vaccines and the situation in Japan

Japanese encephalitis (JE) is a major public health threat in Asia, because of its high mortality and high incidence of psychoneurological sequelae in survivors. It is caused by JE virus (JEV) infection, transmitted by vector mosquitoes. The disease is vaccine preventable and has been well controlled in some countries. Since no specific antivirals have been approved, prevention with vaccine is important in this disease. This article provides a general overview of JE and JEV, but special focus has been put on recently developed Vero cell-derived formalin-inactivated JE vaccines, and the situation in Japan relating to these vaccines. In Japan, where JE has been well controlled, the strong governmental recommendation of the mouse brain-derived vaccine for routine immunization was suspended in 2005, owing to a patient suffering severe postvaccination events. In 2010, the recommendation was reinstated, targeting a limited population utilizing a Vero cell-derived vaccine.

Safety analysis of a Vero-cell culture derived Japanese encephalitis vaccine, IXIARO (IC51), in 6 months of follow-up

Japanese encephalitis (JE) is the most common viral encephalitis in Asia. IXIARO is a Vero cell-derived, inactivated JE virus vaccine which has recently been approved in the US, Europe, Canada and Australia (trade name JESPECT). This overview of the safety and tolerability of IXIARO, for 6 months after the first vaccination in 7 Phase III trials, includes: 3558 subjects with at least one IXIARO vaccination, 435 subjects with a JE-VAX (manufactured by BIKEN, distributed by Sanofi Pasteur) vaccination, and 657 with phosphate-buffered saline solution with 0.1% Al(OH)(3) (PBS+Alum) control vaccination. The percentage of subjects reporting solicited local adverse events (AEs) with IXIARO (54%) was similar to PBS+Alum vaccination (56%) as were solicited systemic adverse events (40% IXIARO; 40% PBS+Alum vaccination). JE-VAX showed a higher frequency of subjects with solicited local adverse events (61%) but a slightly lower frequency of subjects with solicited systemic adverse events (36%). The frequency of subjects with any solicited and unsolicited AE with IXIARO (64%) was also similar to PBS+Alum vaccination (61%) and JE-VAX (64%); as for subjects with serious AEs (1% IXIARO; 2% PBS+Alum vaccination, 1% JE-VAX). No serious allergic reactions were observed in any group. This safety analysis indicates that IXIARO has a favorable safety profile, comparable to PBS+Alum control vaccination and appears to have a better local tolerability profile than JE-VAX.